Remove `Session.used_attrs` and move logic to `CheckAttrVisitor` by Aaron1011 · Pull Request #87739 · rust-lang/rust

Aaron1011 · 2021-08-03T20:56:32Z

Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).

Session.check_name is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
Attribute.has_name

Additionally, AttributeType::AssumedUsed is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in CheckAttrVisitor for a particular attribute.

We no longer emit unused attribute warnings for the #[rustc_dummy]
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.

With this commit, a large source of global untracked state is removed.

rust-highfive · 2021-08-03T20:56:36Z

r? @wesleywiser

(rust-highfive has picked a reviewer for you, use r? to override)

bors · 2021-08-04T04:56:50Z

☔ The latest upstream changes (presumably #87568) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2021-08-12T07:54:35Z

☔ The latest upstream changes (presumably #85296) made this pull request unmergeable. Please resolve the merge conflicts.

wesleywiser · 2021-08-20T16:39:44Z

Seems like a behavior change. Do we need a signoff of some kind to do this?

This attribute is pretty under-specified - it seems to suppress a handful of lints, which aren't documented anywhere. I think the best approach would be to warn when it's used on a non-impl (since impls are the only places where we currently check for it).

Instead of updating global state to mark attributes as used, we now explicitly emit a warning when an attribute is used in an unsupported position. As a side effect, we are to emit more detailed warning messages (instead of just a generic "unused" message). `Session.check_name` is removed, since its only purpose was to mark the attribute as used. All of the callers are modified to use `Attribute.has_name` Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed used' attribute is implemented by simply not performing any checks in `CheckAttrVisitor` for a particular attribute. We no longer emit unused attribute warnings for the `#[rustc_dummy]` attribute - it's an internal attribute used for tests, so it doesn't mark sense to treat it as 'unused'. With this commit, a large source of global untracked state is removed.

Aaron1011 · 2021-08-21T19:12:39Z

@wesleywiser I've addressed your comments

wesleywiser

This looks great to me!

wesleywiser · 2021-08-23T15:28:44Z

@bors r+

bors · 2021-08-23T15:28:45Z

📌 Commit 62aea8c has been approved by wesleywiser

bors · 2021-08-24T03:58:25Z

⌛ Testing commit 62aea8c with merge f66e825...

bors · 2021-08-24T06:39:07Z

☀️ Test successful - checks-actions
Approved by: wesleywiser
Pushing f66e825 to master...

eddyb · 2021-08-27T13:02:48Z

 }
- let check_name = |attr, sym| tcx.sess.check_name(attr, sym);
+ let check_name = |attr: &Attribute, sym| attr.has_name(sym);
 if let Some(name) = weak_lang_items::link_name(check_name, &attrs) {


Can this be inlined into weak_lang_items::link_name? I'm guessing it only took a closure because the Session type wasn't available or something?

Posted #92702 to clean this up.

eddyb · 2021-08-27T13:06:58Z

 pub fn is_proc_macro_attr(&self, attr: &Attribute) -> bool {
 [sym::proc_macro, sym::proc_macro_attribute, sym::proc_macro_derive]
 .iter()
- .any(|kind| self.check_name(attr, *kind))
+ .any(|kind| attr.has_name(*kind))
 }

 pub fn contains_name(&self, attrs: &[Attribute], name: Symbol) -> bool {
- attrs.iter().any(|item| self.check_name(item, name))
+ attrs.iter().any(|item| item.has_name(name))
 }

 pub fn find_by_name<'a>(
 &'a self,
 attrs: &'a [Attribute],
 name: Symbol,
 ) -> Option<&'a Attribute> {
- attrs.iter().find(|attr| self.check_name(attr, name))
+ attrs.iter().find(|attr| attr.has_name(name))
 }

 pub fn filter_by_name<'a>(
 &'a self,
 attrs: &'a [Attribute],
 name: Symbol,
 ) -> impl Iterator<Item = &'a Attribute> {
- attrs.iter().filter(move |attr| self.check_name(attr, name))
+ attrs.iter().filter(move |attr| attr.has_name(name))
 }

 pub fn first_attr_value_str_by_name(
 &self,
 attrs: &[Attribute],
 name: Symbol,
 ) -> Option<Symbol> {
- attrs.iter().find(|at| self.check_name(at, name)).and_then(|at| at.value_str())
+ attrs.iter().find(|at| at.has_name(name)).and_then(|at| at.value_str())
 }


Do any of these methods need to be on Session, or can they be moved back to being on the attributes themselves?

eddyb · 2021-08-27T13:14:59Z

 let attrs = self.tcx.hir().attrs(hir_id);
- let check_name = |attr, sym| self.tcx.sess.check_name(attr, sym);
+ let check_name = |attr: &Attribute, sym| attr.has_name(sym);
 if let Some((value, span)) = extract(check_name, &attrs) {


Same here as with the weak lang items, I'm guessing?

eddyb · 2021-08-27T13:22:09Z

+ fn check_stability_promotable(&self, attr: &Attribute, _span: &Span, target: Target) -> bool {
+ match target {
+ Target::Expression => {
+ self.tcx
+ .sess
+ .struct_span_err(attr.span, "attribute cannot be applied to an expression")
+ .emit();
+ false
+ }
+ _ => true,
+ }
+ }
+
+ fn check_deprecated(&self, hir_id: HirId, attr: &Attribute, _span: &Span, target: Target) {
+ match target {
+ Target::Closure | Target::Expression | Target::Statement | Target::Arm => {
+ self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
+ lint.build("attribute is ignored here").emit();
+ });
+ }
+ _ => {}
+ }
+ }


Shouldn't these checks have lists of allowed Targets, as opposed to disallowed Targets?

eddyb · 2021-08-27T13:23:44Z

+ | sym::unstable
+ | sym::stable
+ | sym::rustc_promotable => self.check_stability_promotable(&attr, span, target),
 _ => true,


If we're handling all the builtin attributes, shouldn't we disallow unknown attributes?

Maybe this could be an exhaustive match over an enum generated by rustc_feature::builtin_attrs? So that there's no way it can go out of sync.

Noted in rust-lang#87739 (review), lang_items::extract no longer needs to take a closure.

…etrochenkov Clean up lang_items::extract Noted in rust-lang#87739 (review), lang_items::extract no longer needs to take a closure.

rust-highfive assigned wesleywiser Aug 3, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 3, 2021

petrochenkov self-assigned this Aug 3, 2021

petrochenkov reviewed Aug 5, 2021
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Comment threadcompiler/rustc_expand/src/expand.rs Outdated

petrochenkov removed their assignment Aug 5, 2021

Aaron1011 force-pushed the remove-used-attrs branch from 0d06da4 to fe702a4Compare August 5, 2021 22:59

wesleywiser reviewed Aug 20, 2021
View reviewed changes

Aaron1011 added 3 commits August 21, 2021 13:27

Remove NonMacroAttr.mark_used
17aef21

Address review comments
62aea8c

Aaron1011 force-pushed the remove-used-attrs branch from fe702a4 to 62aea8cCompare August 21, 2021 19:12

wesleywiser approved these changes Aug 23, 2021
View reviewed changes

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 23, 2021

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 24, 2021

bors merged commit f66e825 into rust-lang:masterAug 24, 2021

rustbot added this to the 1.56.0 milestone Aug 24, 2021

This was referenced Aug 24, 2021
Make AST->HIR lowering incremental #88186
Closed
Refactor named_asm_labels to a HIR lint #88196
Merged

eddyb reviewed Aug 27, 2021
View reviewed changes

ehuss mentioned this pull request Sep 6, 2021
Check for duplicate attributes. #88681
Merged

ehuss mentioned this pull request Nov 12, 2021
Add passes to mark stability and must-use attributes as used #14407
Closed

ehuss added a commit to ehuss/rust that referenced this pull request Jan 9, 2022
Clean up lang_items::extract
2b75720
Noted in rust-lang#87739 (review), lang_items::extract no longer needs to take a closure.

ehuss mentioned this pull request Jan 9, 2022
Clean up lang_items::extract #92702
Merged

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