mGCA: Validate const literal against expected type by reddevilmidzy · Pull Request #152001 · rust-lang/rust

reddevilmidzy · 2026-02-02T16:10:33Z

also fix: #133966 (moved crashes test)

BoxyUwU · 2026-02-04T12:44:13Z

very cool :) thanks for working on this

…=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see rust-lang#152139 rust-lang#152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixesrust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though

Rollup merge of #152234 - BoxyUwU:dont_strip_const_blocks, r=oli-obk Dont strip const blocks in array lengths r? oli-obk mGCA now handles const blocks by *always* handling them during `lower_expr_to_const_arg_direct` instead of *sometimes* stripping them out at parse time. This is just generally a lot clearer/nicer but also means parsing isn't lossy which is just straight up wrong. We now use `MgcaDisambiguation::Direct` for const blocks because we "directly" represent a const block as `hir::ConstArgKind::Anon` :> The only time that an anon const for const generics uses `MgcaDisambiguation::AnonConst` is for unbraced literals. Once we properly support literals in `hir::ConstArgKind` (see #152139 #152001) then `MgcaDisambiguation` can be renamed to `AnonConstKind` with `TypeSystem` and `NonTypeSystem` variants. We can also get rid of `mgca_direct_lit_hack`. I expect this to be a very nice cleanup :) Fixesrust-lang/rustfmt#6788 The diff relating to passing spans around is to avoid a bunch of mGCA diagnostics changing from `const {}` to `{}`. I'm not entirely sure why this was happening. cc @rust-lang/rustfmt How do I run the tests in the rustfmt repo from here? `x test rustfmt` only seems to run like 100 tests and doesn't result in a `target/issue-6788.rs` getting created. I've verified locally that this formats correctly though

reddevilmidzy · 2026-02-07T12:19:39Z

Haha, ICE occurs in other tests...

reddevilmidzy

Thanks for your quick review. 😊

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reddevilmidzy

In ten crash tests, the ICE disappeared; however, in ‎tests/crashes/117460.rs, tests/crashes/114212-2.rs and tests/crashes/114212.rs, adding the main function caused the ICE to occur again.

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reddevilmidzy · 2026-02-08T09:12:14Z

@@ -0,0 +1,23 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/116554>


This issue was closed; is there a need to add further testing?

unsure, I will look over all the GCE tests (outside of this PR) at some point soon and see which ones are worth keeping

reddevilmidzy · 2026-02-08T09:35:23Z

Could the following issues also be closed? 🤔

#119824
#133966
#136416

already closed
#94846
#106473
#116554

…uwer Rollup of 8 pull requests Successful merges: - #152618 (stdarch subtree update) - #152001 (mGCA: Validate const literal against expected type) - #152120 (Don't ICE on layout error in vtable computation) - #152531 (`proc_macro::bridge`: simplify `ExecutionStrategy` and `DispatcherTrait`) - #152577 (Port #[rustc_proc_macro_decls] to the new attribute parser.) - #152570 (Port #[rustc_test_marker] to the attribute parser) - #152590 (DepGraphQuery: correctly skip adding edges with not-yet-added nodes) - #152612 (Rename `inline_fluent!` to `msg!`)

Rollup merge of #152001 - reddevilmidzy:mgca-i, r=BoxyUwU mGCA: Validate const literal against expected type close: #151625close: #150983 also fix: #133966 (moved crashes test)

…uwer Rollup of 8 pull requests Successful merges: - rust-lang/rust#152618 (stdarch subtree update) - rust-lang/rust#152001 (mGCA: Validate const literal against expected type) - rust-lang/rust#152120 (Don't ICE on layout error in vtable computation) - rust-lang/rust#152531 (`proc_macro::bridge`: simplify `ExecutionStrategy` and `DispatcherTrait`) - rust-lang/rust#152577 (Port #[rustc_proc_macro_decls] to the new attribute parser.) - rust-lang/rust#152570 (Port #[rustc_test_marker] to the attribute parser) - rust-lang/rust#152590 (DepGraphQuery: correctly skip adding edges with not-yet-added nodes) - rust-lang/rust#152612 (Rename `inline_fluent!` to `msg!`)

mGCA: Lower negated literals directly and reject non-integer negations follow up rust-lang#152001resolve: rust-lang#152246 r? BoxyUwU

Rollup merge of #153075 - reddevilmidzy:mgca-neg, r=BoxyUwU mGCA: Lower negated literals directly and reject non-integer negations follow up #152001resolve: #152246 r? BoxyUwU

Fix ICE in `try_to_raw_bytes` when array elements have mismatched close: rust-lang#152683 After rust-lang#152001, suffixed integer literals preserve their own type during const lowering, so `try_to_raw_bytes` could call `.to_u8()` on a scalar with size > 1, causing an ICE. Fix by using `try_to_bits(Size::from_bytes(1)).ok()` instead. r? BoxyUwU

Rollup merge of #152794 - reddevilmidzy:mgca-print, r=BoxyUwU Fix ICE in `try_to_raw_bytes` when array elements have mismatched close: #152683 After #152001, suffixed integer literals preserve their own type during const lowering, so `try_to_raw_bytes` could call `.to_u8()` on a scalar with size > 1, causing an ICE. Fix by using `try_to_bits(Size::from_bytes(1)).ok()` instead. r? BoxyUwU

Fix ICE in `try_to_raw_bytes` when array elements have mismatched close: rust-lang/rust#152683 After rust-lang/rust#152001, suffixed integer literals preserve their own type during const lowering, so `try_to_raw_bytes` could call `.to_u8()` on a scalar with size > 1, causing an ICE. Fix by using `try_to_bits(Size::from_bytes(1)).ok()` instead. r? BoxyUwU

oli-obk · 2026-05-12T06:58:15Z

+ match tcx.at(span).lit_to_const(input) {
+ Some(value) => ty::Const::new_value(tcx, value.valtree, value.ty),
+ None => {
+ let e = tcx.dcx().span_err(span, "type annotations needed for the literal");


This is the cause of the ICEs you're seeing I think. You need to do self.dcx() to make sure that the lowering context gets tainted
View changes since the review

…uwer Rollup of 8 pull requests Successful merges: - rust-lang/rust#152618 (stdarch subtree update) - rust-lang/rust#152001 (mGCA: Validate const literal against expected type) - rust-lang/rust#152120 (Don't ICE on layout error in vtable computation) - rust-lang/rust#152531 (`proc_macro::bridge`: simplify `ExecutionStrategy` and `DispatcherTrait`) - rust-lang/rust#152577 (Port #[rustc_proc_macro_decls] to the new attribute parser.) - rust-lang/rust#152570 (Port #[rustc_test_marker] to the attribute parser) - rust-lang/rust#152590 (DepGraphQuery: correctly skip adding edges with not-yet-added nodes) - rust-lang/rust#152612 (Rename `inline_fluent!` to `msg!`)

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Feb 2, 2026

reddevilmidzy commented Feb 2, 2026
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Comment threadtests/ui/const-generics/mgca/literal-type-mismatch.rs Outdated

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BoxyUwU self-assigned this Feb 3, 2026

reddevilmidzy force-pushed the mgca-i branch from b401801 to e08830eCompare February 4, 2026 03:48

BoxyUwU reviewed Feb 4, 2026
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Comment threadcompiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs Outdated

BoxyUwU mentioned this pull request Feb 4, 2026
mGCA: Support directly represented negated literals #152123
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khyperia mentioned this pull request Feb 6, 2026
mGCA: Support directly represented negated literals #152139
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This was referenced Feb 6, 2026
Dont strip const blocks in array lengths #152234
Merged
mGCA: remove parser special case for literals #152246
Closed

rust-cloud-vmsBotforce-pushed the mgca-i branch from e08830e to cd5b323Compare February 7, 2026 10:09

BoxyUwU reviewed Feb 7, 2026
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Comment threadcompiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs Outdated

BoxyUwU reviewed Feb 7, 2026
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Comment threadcompiler/rustc_mir_build/src/thir/constant.rs Outdated

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rust-cloud-vmsBotforce-pushed the mgca-i branch from ac69206 to ca77eabCompare February 7, 2026 16:16

reddevilmidzy commented Feb 7, 2026
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Comment threadcompiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs Outdated
Comment threadtests/ui/const-generics/mgca/type_const-mismatched-types.rs Outdated

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reddevilmidzy commented Feb 8, 2026
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rust-cloud-vmsBotforce-pushed the mgca-i branch from 75e7e18 to 2b5c8b7Compare February 8, 2026 14:37

rust-borsBot merged commit 5ae6bb3 into rust-lang:mainFeb 14, 2026
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rustbot added this to the 1.95.0 milestone Feb 14, 2026

rust-timer added a commit that referenced this pull request Feb 14, 2026
Unrolled build for#152001
b5fd2a5
Rollup merge of #152001 - reddevilmidzy:mgca-i, r=BoxyUwU mGCA: Validate const literal against expected type close: #151625close: #150983 also fix: #133966 (moved crashes test)

reddevilmidzy deleted the mgca-i branch February 15, 2026 00:41

This was referenced Feb 15, 2026
[ICE]: Binder / Cond<UnevaluatedConst has parameters, but no args were provided in instantiate #152647
Open
[ICE]: attempting to project to field at offset 0 with size 8 into immediate #152653
Closed
[ICE]: expected int of size 1, but got size 8#152683
Closed

reddevilmidzy mentioned this pull request Feb 18, 2026
Fix ICE in try_to_raw_bytes when array elements have mismatched #152794
Merged

lapla-cogito mentioned this pull request Feb 20, 2026
Make const_lit_matches_ty check literal suffixes for exact type match #152906
Merged

reddevilmidzy mentioned this pull request Feb 25, 2026
mGCA: Lower negated literals directly and reject non-integer negations #153075
Merged

jhpratt added a commit to jhpratt/rust that referenced this pull request Feb 26, 2026
Rollup merge ofrust-lang#153075- reddevilmidzy:mgca-neg, r=BoxyUwU
cd09c56
mGCA: Lower negated literals directly and reject non-integer negations follow up rust-lang#152001resolve: rust-lang#152246 r? BoxyUwU

rust-timer added a commit that referenced this pull request Feb 26, 2026
Unrolled build for#153075
eb9365b
Rollup merge of #153075 - reddevilmidzy:mgca-neg, r=BoxyUwU mGCA: Lower negated literals directly and reject non-integer negations follow up #152001resolve: #152246 r? BoxyUwU

BoxyUwU mentioned this pull request Feb 28, 2026
Tracking Issue for Generic Constant Arguments MVP #132980
Open
29 tasks

reddevilmidzy mentioned this pull request Apr 4, 2026
[ICE]: invalid field access on immediate #154748
Closed

oli-obk reviewed May 12, 2026
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		@@ -0,0 +1,23 @@
		//! Regression test for <https://github.com/rust-lang/rust/issues/116554>

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