[pull] main from react:main#643

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Merged
pull merged 4 commits into from
Aug 24, 2026
Merged

[pull] main from react:main #643

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05769e0
React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…
andrewimm Aug 24, 2026
8c94e0e
React Compiler: Avoid unnecessary clone in effect inference (#37207)
andrewimm Aug 24, 2026
b939280
React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)
andrewimm Aug 24, 2026
3d05080
[Fizz] Construct the render lifetime controller only when it is neede…
unstubbable Aug 24, 2026
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157 changes: 110 additions & 47 deletions compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
value_id,
AbstractValue {
kind: ValueKind::Context,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
},
);
initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
let param_kind: AbstractValue = if is_function_expression {
AbstractValue {
kind: ValueKind::Mutable,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
}
} else {
AbstractValue {
kind: ValueKind::Frozen,
reason: hashset_of(ValueReason::ReactiveFunctionArgument),
reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
}
};

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
value_id,
AbstractValue {
kind: ValueKind::Mutable,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
},
);
initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
};

states_by_block.insert(block_id, incoming_state.clone());
let mut state = incoming_state.clone();
let mut state = incoming_state;

infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
kind: ValueKind,
reason: IndexSet<ValueReason, FxBuildHasher>,
reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
/// Members in insertion order. Only the first `len` entries are meaningful.
members: [ValueReason; VALUE_REASON_CAPACITY],
len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
let mut s = IndexSet::default();
s.insert(r);
s
impl Default for ValueReasonSet {
fn default() -> Self {
ValueReasonSet {
members: [ValueReason::Other; VALUE_REASON_CAPACITY],
len: 0,
}
}
}

impl ValueReasonSet {
fn single(reason: ValueReason) -> Self {
let mut set = Self::default();
set.insert(reason);
set
}

fn contains(&self, reason: ValueReason) -> bool {
self.members[..self.len as usize].contains(&reason)
}

fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
self.members[..self.len as usize].iter().copied()
}

/// Appends `reason` if not already present, preserving insertion order.
fn insert(&mut self, reason: ValueReason) {
if self.contains(reason) {
return;
}
debug_assert!(
(self.len as usize) < VALUE_REASON_CAPACITY,
"ValueReasonSet capacity must cover every ValueReason variant"
);
if (self.len as usize) < VALUE_REASON_CAPACITY {
self.members[self.len as usize] = reason;
self.len += 1;
}
}

/// True when every member of `other` is also a member of `self`.
fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
other.iter().all(|reason| self.contains(reason))
}

/// Adds every member of `other`, keeping `self`'s existing order and
/// appending newcomers in `other`'s order — matching `IndexSet::insert`.
fn union_with(&mut self, other: &ValueReasonSet) {
for reason in other.iter() {
self.insert(reason);
}
}
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
}
return AbstractValue {
kind: ValueKind::Mutable,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
};
}
};
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
}
merged_kind.unwrap_or_else(|| AbstractValue {
kind: ValueKind::Mutable,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
})
}

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
vid,
AbstractValue {
kind: ValueKind::Mutable,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
},
);
}
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
value_id,
AbstractValue {
kind: ValueKind::Frozen,
reason: hashset_of(reason),
reason: ValueReasonSet::single(reason),
},
);
// Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
if let Some(other_value) = other.values.get(id) {
let merged = merge_abstract_values(this_value, other_value);
if merged.kind != this_value.kind
|| !is_superset(&this_value.reason, &merged.reason)
|| !this_value.reason.is_superset_of(&merged.reason)
{
let nv = next_values.get_or_insert_with(|| self.values.clone());
nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
}
}

fn is_superset(
a: &IndexSet<ValueReason, FxBuildHasher>,
b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
let kind = merge_value_kinds(a.kind, b.kind);
if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
return a.clone();
}
let mut reason = a.reason.clone();
for r in &b.reason {
reason.insert(*r);
}
let mut reason = a.reason;
reason.union_with(&b.reason);
AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
vid,
AbstractValue {
kind: ValueKind::Mutable,
reason: hashset_of(ValueReason::Other),
reason: ValueReasonSet::single(ValueReason::Other),
},
);
state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
value_id,
AbstractValue {
kind,
reason: hashset_of(reason),
reason: ValueReasonSet::single(reason),
},
);
state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
value_id,
AbstractValue {
kind: from_value.kind,
reason: from_value.reason.clone(),
reason: from_value.reason,
},
);
state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
} else {
ValueKind::Frozen
},
reason: IndexSet::default(),
reason: ValueReasonSet::default(),
},
);
state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
value_id,
AbstractValue {
kind: from_value.kind,
reason: from_value.reason.clone(),
reason: from_value.reason,
},
);
state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
value_id,
AbstractValue {
kind: from_value.kind,
reason: from_value.reason.clone(),
reason: from_value.reason,
},
);
state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
for r in reasons.iter() {
if r != ValueReason::Other {
return r;
}
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
if abstract_value.reason.contains(&ValueReason::Global) {
if abstract_value.reason.contains(ValueReason::Global) {
"Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
} else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
} else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
"Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
} else if abstract_value.reason.contains(&ValueReason::Context) {
} else if abstract_value.reason.contains(ValueReason::Context) {
"Modifying a value returned from 'useContext()' is not allowed.".to_string()
} else if abstract_value
.reason
.contains(&ValueReason::KnownReturnSignature)
.contains(ValueReason::KnownReturnSignature)
{
"Modifying a value returned from a function whose return value should not be mutated"
.to_string()
} else if abstract_value
.reason
.contains(&ValueReason::ReactiveFunctionArgument)
.contains(ValueReason::ReactiveFunctionArgument)
{
"Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
} else if abstract_value.reason.contains(&ValueReason::State) {
} else if abstract_value.reason.contains(ValueReason::State) {
"Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
} else if abstract_value.reason.contains(&ValueReason::ReducerState) {
} else if abstract_value.reason.contains(ValueReason::ReducerState) {
"Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
} else if abstract_value.reason.contains(&ValueReason::Effect) {
} else if abstract_value.reason.contains(ValueReason::Effect) {
"Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
} else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
} else if abstract_value.reason.contains(ValueReason::HookCaptured) {
"Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
} else if abstract_value.reason.contains(&ValueReason::HookReturn) {
} else if abstract_value.reason.contains(ValueReason::HookReturn) {
"Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
} else {
"This modifies a variable that React considers immutable".to_string()
Expand Down
34 changes: 19 additions & 15 deletions compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
}

// Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
.iter()
.filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
.filter_map(|n| working.get(n).cloned())
.collect();
let neighbor_intersection = {
let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
.iter()
.filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
.filter_map(|n| working.get(n))
.collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
match done_neighbor_sets.split_first() {
None => BTreeSet::new(),
Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
acc.intersection(s).copied().collect()
}),
}
};

let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
// Temporarily remove the previous set out of the map so it can be safely
// borrowed and compared without a heavy deep clone.
let prev_objects = working.remove(&node_id).unwrap_or_default();
let mut merged: BTreeSet<usize> = prev_objects
.union(&neighbor_intersection)
.copied()
.collect();
reduce_maybe_optional_chains(&mut merged, registry);

working.insert(node_id, merged.clone());
traversal_state.insert(node_id, TraversalState::Done);

// Compare with previous value — can't just check size due to reduce_maybe_optional_chains
changed |= prev_objects != merged;

working.insert(node_id, merged);
traversal_state.insert(node_id, TraversalState::Done);

changed
}

Expand Down
Loading
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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[pull] main from react:main#643

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to your account

 Merged

pull
merged 4 commits into

from

Aug 24, 2026
 Merged


[pull] main from react:main
#643
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05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[pull] main from react:main#643

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pull
merged 4 commits into

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Aug 24, 2026
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[pull] main from react:main
#643
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05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[pull] main from react:main#643

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to your account

 Merged

pull
merged 4 commits into

from

Aug 24, 2026
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[pull] main from react:main
#643
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05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
Loading
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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 Merged

pull
merged 4 commits into

from

Aug 24, 2026
 Merged


[pull] main from react:main
#643
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4 commits


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Hold shift + click to select a range
05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[pull] main from react:main#643

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 Merged

pull
merged 4 commits into

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Aug 24, 2026
 Merged


[pull] main from react:main
#643
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05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[pull] main from react:main#643

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

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to your account

 Merged

pull
merged 4 commits into

from

Aug 24, 2026
 Merged


[pull] main from react:main
#643
Show file tree
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4 commits


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Hold shift + click to select a range
05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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Filter by extension
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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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Aug 24, 2026
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[pull] main from react:main
#643
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05769e0

React Compiler: Make AbstractValue Copy to reduce heap allocation (#3…


andrewimm Aug 24, 2026
8c94e0e

React Compiler: Avoid unnecessary clone in effect inference (#37207)


andrewimm Aug 24, 2026
b939280

React Compiler: avoid deep ast clone and quadratic-time codegen (#37206)


andrewimm Aug 24, 2026
3d05080

[Fizz] Construct the render lifetime controller only when it is neede…


unstubbable Aug 24, 2026

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157 changes: 110 additions & 47 deletions
compiler/crates/react_compiler_inference/src/infer_mutation_aliasing_effects.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -11,7 +11,7 @@
//! creation, aliasing, mutation, freezing, and error conditions for each
//! instruction and terminal in the HIR.

use indexmap::{IndexMap, IndexSet};
use indexmap::IndexMap;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};

use react_compiler_diagnostics::CompilerDiagnostic;
Expand DownExpand Up@@ -69,7 +69,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Context,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ctx_place.identifier, value_id);
Expand All@@ -78,12 +78,12 @@ pub fn infer_mutation_aliasing_effects(
 let param_kind: AbstractValue = if is_function_expression {
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 }
 } else {
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(ValueReason::ReactiveFunctionArgument),
 reason: ValueReasonSet::single(ValueReason::ReactiveFunctionArgument),
 }
 };

Expand All@@ -103,7 +103,7 @@ pub fn infer_mutation_aliasing_effects(
 value_id,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 initial_state.define(ref_place.identifier, value_id);
Expand DownExpand Up@@ -185,7 +185,7 @@ pub fn infer_mutation_aliasing_effects(
 };

 states_by_block.insert(block_id, incoming_state.clone());
 let mut state = incoming_state.clone();
 let mut state = incoming_state;

 infer_block(&mut context, &mut state, block_id, func, env)?;

Expand DownExpand Up@@ -258,16 +258,88 @@ impl ValueId {
// AbstractValue
// =============================================================================

#[derive(Debug, Clone)]
#[derive(Debug, Clone, Copy)]
struct AbstractValue {
 kind: ValueKind,
 reason: IndexSet<ValueReason, FxBuildHasher>,
 reason: ValueReasonSet,
}

/// Capacity of [`ValueReasonSet`]. A set holds at most one of each `ValueReason`
/// variant, of which there are currently 12; the extra slots are headroom so
/// that adding variants upstream cannot overflow the set.
const VALUE_REASON_CAPACITY: usize = 16;

/// An insertion-ordered set of [`ValueReason`]s, stored inline.
///
/// This is a deliberate replacement for `IndexSet`, enabling insertion-order
/// memory while avoiding any heap allocation. At `AbstractValue`'s scale, this
/// has a dramatic impact on heap memory and wall time.
/// This takes advantage of the format of the data it's actually storing. A set
/// can hold at most one of each variant, so the members fit into a fixed inline
/// array. `ValueReason` is implemented as a single byte, so this struct is
/// ~18 bytes on the stack.
///
/// Insertion order is preserved deliberately: [`primary_reason`] returns the
/// first non-`Other` member, matching the iteration order of the `Set` used by
/// the TypeScript implementation this is ported from.
#[derive(Debug, Clone, Copy)]
struct ValueReasonSet {
 /// Members in insertion order. Only the first `len` entries are meaningful.
 members: [ValueReason; VALUE_REASON_CAPACITY],
 len: u8,
}

fn hashset_of(r: ValueReason) -> IndexSet<ValueReason, FxBuildHasher> {
 let mut s = IndexSet::default();
 s.insert(r);
 s
impl Default for ValueReasonSet {
 fn default() -> Self {
 ValueReasonSet {
 members: [ValueReason::Other; VALUE_REASON_CAPACITY],
 len: 0,
 }
 }
}

impl ValueReasonSet {
 fn single(reason: ValueReason) -> Self {
 let mut set = Self::default();
 set.insert(reason);
 set
 }

 fn contains(&self, reason: ValueReason) -> bool {
 self.members[..self.len as usize].contains(&reason)
 }

 fn iter(&self) -> impl Iterator<Item = ValueReason> + '_ {
 self.members[..self.len as usize].iter().copied()
 }

 /// Appends `reason` if not already present, preserving insertion order.
 fn insert(&mut self, reason: ValueReason) {
 if self.contains(reason) {
 return;
 }
 debug_assert!(
 (self.len as usize) < VALUE_REASON_CAPACITY,
 "ValueReasonSet capacity must cover every ValueReason variant"
 );
 if (self.len as usize) < VALUE_REASON_CAPACITY {
 self.members[self.len as usize] = reason;
 self.len += 1;
 }
 }

 /// True when every member of `other` is also a member of `self`.
 fn is_superset_of(&self, other: &ValueReasonSet) -> bool {
 other.iter().all(|reason| self.contains(reason))
 }

 /// Adds every member of `other`, keeping `self`'s existing order and
 /// appending newcomers in `other`'s order — matching `IndexSet::insert`.
 fn union_with(&mut self, other: &ValueReasonSet) {
 for reason in other.iter() {
 self.insert(reason);
 }
 }
}

// =============================================================================
Expand DownExpand Up@@ -315,7 +387,7 @@ impl InferenceState {
 }
 return AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 };
 }
 };
Expand All@@ -332,7 +404,7 @@ impl InferenceState {
 }
 merged_kind.unwrap_or_else(|| AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 })
 }

Expand DownExpand Up@@ -360,7 +432,7 @@ impl InferenceState {
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 }
Expand DownExpand Up@@ -438,7 +510,7 @@ impl InferenceState {
 value_id,
 AbstractValue {
 kind: ValueKind::Frozen,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 // Note: In TS, this also transitively freezes FunctionExpression captures
Expand DownExpand Up@@ -493,7 +565,7 @@ impl InferenceState {
 if let Some(other_value) = other.values.get(id) {
 let merged = merge_abstract_values(this_value, other_value);
 if merged.kind != this_value.kind
 || !is_superset(&this_value.reason, &merged.reason)
 || !this_value.reason.is_superset_of(&merged.reason)
 {
 let nv = next_values.get_or_insert_with(|| self.values.clone());
 nv.insert(*id, merged);
Expand DownExpand Up@@ -566,13 +638,6 @@ impl InferenceState {
 }
}

fn is_superset(
 a: &IndexSet<ValueReason, FxBuildHasher>,
 b: &IndexSet<ValueReason, FxBuildHasher>,
) -> bool {
 b.iter().all(|x| a.contains(x))
}

#[derive(Debug, Clone, Copy)]
enum MutateVariant {
 Mutate,
Expand DownExpand Up@@ -738,13 +803,11 @@ fn hash_effect(effect: &AliasingEffect) -> String {

fn merge_abstract_values(a: &AbstractValue, b: &AbstractValue) -> AbstractValue {
 let kind = merge_value_kinds(a.kind, b.kind);
 if kind == a.kind && kind == b.kind && is_superset(&a.reason, &b.reason) {
 if kind == a.kind && kind == b.kind && a.reason.is_superset_of(&b.reason) {
 return a.clone();
 }
 let mut reason = a.reason.clone();
 for r in &b.reason {
 reason.insert(*r);
 }
 let mut reason = a.reason;
 reason.union_with(&b.reason);
 AbstractValue { kind, reason }
}

Expand DownExpand Up@@ -1233,7 +1296,7 @@ fn apply_signature(
 vid,
 AbstractValue {
 kind: ValueKind::Mutable,
 reason: hashset_of(ValueReason::Other),
 reason: ValueReasonSet::single(ValueReason::Other),
 },
 );
 state.define(instr.lvalue.identifier, vid);
Expand DownExpand Up@@ -1341,7 +1404,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind,
 reason: hashset_of(reason),
 reason: ValueReasonSet::single(reason),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1370,7 +1433,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1487,7 +1550,7 @@ fn apply_effect(
 } else {
 ValueKind::Frozen
 },
 reason: IndexSet::default(),
 reason: ValueReasonSet::default(),
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -1599,7 +1662,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand All@@ -1615,7 +1678,7 @@ fn apply_effect(
 value_id,
 AbstractValue {
 kind: from_value.kind,
 reason: from_value.reason.clone(),
 reason: from_value.reason,
 },
 );
 state.define(into.identifier, value_id);
Expand DownExpand Up@@ -3410,8 +3473,8 @@ fn compute_effects_for_aliasing_signature(
/// since the primary reason is always inserted first, this effectively
/// picks the most specific non-Other reason. We replicate this by
/// preferring any non-Other reason over Other.
fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason {
 for &r in reasons {
fn primary_reason(reasons: &ValueReasonSet) -> ValueReason {
 for r in reasons.iter() {
 if r != ValueReason::Other {
 return r;
 }
Expand All@@ -3420,32 +3483,32 @@ fn primary_reason(reasons: &IndexSet<ValueReason, FxBuildHasher>) -> ValueReason
}

fn get_write_error_reason(abstract_value: &AbstractValue) -> String {
 if abstract_value.reason.contains(&ValueReason::Global) {
 if abstract_value.reason.contains(ValueReason::Global) {
 "Modifying a variable defined outside a component or hook is not allowed. Consider using an effect".to_string()
 } else if abstract_value.reason.contains(&ValueReason::JsxCaptured) {
 } else if abstract_value.reason.contains(ValueReason::JsxCaptured) {
 "Modifying a value used previously in JSX is not allowed. Consider moving the modification before the JSX".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Context) {
 } else if abstract_value.reason.contains(ValueReason::Context) {
 "Modifying a value returned from 'useContext()' is not allowed.".to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::KnownReturnSignature)
 .contains(ValueReason::KnownReturnSignature)
 {
 "Modifying a value returned from a function whose return value should not be mutated"
 .to_string()
 } else if abstract_value
 .reason
 .contains(&ValueReason::ReactiveFunctionArgument)
 .contains(ValueReason::ReactiveFunctionArgument)
 {
 "Modifying component props or hook arguments is not allowed. Consider using a local variable instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::State) {
 } else if abstract_value.reason.contains(ValueReason::State) {
 "Modifying a value returned from 'useState()', which should not be modified directly. Use the setter function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::ReducerState) {
 } else if abstract_value.reason.contains(ValueReason::ReducerState) {
 "Modifying a value returned from 'useReducer()', which should not be modified directly. Use the dispatch function to update instead".to_string()
 } else if abstract_value.reason.contains(&ValueReason::Effect) {
 } else if abstract_value.reason.contains(ValueReason::Effect) {
 "Modifying a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the modification before calling useEffect()".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookCaptured) {
 } else if abstract_value.reason.contains(ValueReason::HookCaptured) {
 "Modifying a value previously passed as an argument to a hook is not allowed. Consider moving the modification before calling the hook".to_string()
 } else if abstract_value.reason.contains(&ValueReason::HookReturn) {
 } else if abstract_value.reason.contains(ValueReason::HookReturn) {
 "Modifying a value returned from a hook is not allowed. Consider moving the modification into the hook where the value is constructed".to_string()
 } else {
 "This modifies a variable that React considers immutable".to_string()
Expand Down

34 changes: 19 additions & 15 deletions
compiler/crates/react_compiler_inference/src/propagate_scope_dependencies_hir.rs

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1472,32 +1472,36 @@ fn recursively_propagate_non_null(
 }

 // Compute intersection of 'done' neighbors only (filter out 'active' = cycle nodes)
 let done_neighbor_sets: Vec<BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n).cloned())
 .collect();
 let neighbor_intersection = {
 let done_neighbor_sets: Vec<&BTreeSet<usize>> = neighbors
 .iter()
 .filter(|n| traversal_state.get(n) == Some(&TraversalState::Done))
 .filter_map(|n| working.get(n))
 .collect();

let neighbor_intersection = if done_neighbor_sets.is_empty() {
 BTreeSet::new()
} else {
let mut iter = done_neighbor_sets.into_iter();
let first = iter.next().unwrap();
iter.fold(first, |acc, s| acc.intersection(&s).copied().collect())
 match done_neighbor_sets.split_first() {
 None => BTreeSet::new(),
 Some((first, rest)) => rest.iter().fold((*first).clone(), |acc, s| {
 acc.intersection(s).copied().collect()
 }),
}
 };

 let prev_objects = working.get(&node_id).cloned().unwrap_or_default();
 // Temporarily remove the previous set out of the map so it can be safely
 // borrowed and compared without a heavy deep clone.
 let prev_objects = working.remove(&node_id).unwrap_or_default();
 let mut merged: BTreeSet<usize> = prev_objects
 .union(&neighbor_intersection)
 .copied()
 .collect();
 reduce_maybe_optional_chains(&mut merged, registry);

 working.insert(node_id, merged.clone());
 traversal_state.insert(node_id, TraversalState::Done);

 // Compare with previous value — can't just check size due to reduce_maybe_optional_chains
 changed |= prev_objects != merged;

 working.insert(node_id, merged);
 traversal_state.insert(node_id, TraversalState::Done);

 changed
}

Expand Down
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