Rollup merge of rust-lang#111757 - lowr:fix/lint-attr-on-match-arm, r=eholk

Consider lint check attributes on match arms

Currently, lint check attributes on match arms have no effect for some lints. This PR makes some lint passes to take those attributes into account.

- `LateContextAndPass` for late lint doesn't update `last_node_with_lint_attrs` when it visits match arms. This leads to lint check attributes on match arms taking no effects on late lints that operate on the arms' pattern:

  ```rust
  match value {
      #[deny(non_snake_case)]
      PAT => {} // `non_snake_case` only warned due to default lint level
  }
  ```

  To be honest, I'm not sure whether this is intentional or just an oversight. I've dug the implementation history and searched up issues/PRs but couldn't find any discussion on this.

- `MatchVisitor` doesn't update its lint level when it visits match arms. This leads to check lint attributes on match arms taking no effect on some lints handled by this visitor, namely: `bindings_with_variant_name` and `irrefutable_let_patterns`.

  This seems to be a fallout from rust-lang#108504. Before 05082f5, when the visitor operated on HIR rather than THIR, check lint attributes for the said lints were effective. [This playground][play] compiles successfully on current stable (1.69) but fails on current beta and nightly.

  I wasn't sure where best to place the test for this. Let me know if there's a better place.

[play]: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=38432b79e535cb175f8f7d6d236d29c3
[play-match]: https://play.rust-lang.org/?version=beta&mode=debug&edition=2021&gist=629aa71b7c84b269beadeba664e2221d

Author: compiler-errors

compiler/rustc_lint/src/late.rs

@@ -240,8 +240,10 @@ impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPas
     }
 
     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
-        lint_callback!(self, check_arm, a);
-        hir_visit::walk_arm(self, a);
+        self.with_lint_attrs(a.hir_id, |cx| {
+            lint_callback!(cx, check_arm, a);
+            hir_visit::walk_arm(cx, a);
+        })
     }
 
     fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -90,35 +90,34 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for MatchVisitor<'a, '_, 'tcx> {
 
     #[instrument(level = "trace", skip(self))]
     fn visit_arm(&mut self, arm: &Arm<'tcx>) {
-        match arm.guard {
-            Some(Guard::If(expr)) => {
-                self.with_let_source(LetSource::IfLetGuard, |this| {
-                    this.visit_expr(&this.thir[expr])
-                });
-            }
-            Some(Guard::IfLet(ref pat, expr)) => {
-                self.with_let_source(LetSource::IfLetGuard, |this| {
-                    this.check_let(pat, expr, LetSource::IfLetGuard, pat.span);
-                    this.visit_pat(pat);
-                    this.visit_expr(&this.thir[expr]);
-                });
+        self.with_lint_level(arm.lint_level, |this| {
+            match arm.guard {
+                Some(Guard::If(expr)) => {
+                    this.with_let_source(LetSource::IfLetGuard, |this| {
+                        this.visit_expr(&this.thir[expr])
+                    });
+                }
+                Some(Guard::IfLet(ref pat, expr)) => {
+                    this.with_let_source(LetSource::IfLetGuard, |this| {
+                        this.check_let(pat, expr, LetSource::IfLetGuard, pat.span);
+                        this.visit_pat(pat);
+                        this.visit_expr(&this.thir[expr]);
+                    });
+                }
+                None => {}
             }
-            None => {}
-        }
-        self.visit_pat(&arm.pattern);
-        self.visit_expr(&self.thir[arm.body]);
+            this.visit_pat(&arm.pattern);
+            this.visit_expr(&self.thir[arm.body]);
+        });
     }
 
     #[instrument(level = "trace", skip(self))]
     fn visit_expr(&mut self, ex: &Expr<'tcx>) {
         match ex.kind {
             ExprKind::Scope { value, lint_level, .. } => {
-                let old_lint_level = self.lint_level;
-                if let LintLevel::Explicit(hir_id) = lint_level {
-                    self.lint_level = hir_id;
-                }
-                self.visit_expr(&self.thir[value]);
-                self.lint_level = old_lint_level;
+                self.with_lint_level(lint_level, |this| {
+                    this.visit_expr(&this.thir[value]);
+                });
                 return;
             }
             ExprKind::If { cond, then, else_opt, if_then_scope: _ } => {
@@ -190,6 +189,17 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
         self.let_source = old_let_source;
     }
 
+    fn with_lint_level(&mut self, new_lint_level: LintLevel, f: impl FnOnce(&mut Self)) {
+        if let LintLevel::Explicit(hir_id) = new_lint_level {
+            let old_lint_level = self.lint_level;
+            self.lint_level = hir_id;
+            f(self);
+            self.lint_level = old_lint_level;
+        } else {
+            f(self);
+        }
+    }
+
     fn check_patterns(&self, pat: &Pat<'tcx>, rf: RefutableFlag) {
         pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
         check_for_bindings_named_same_as_variants(self, pat, rf);
@@ -236,7 +246,9 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
         for &arm in arms {
             // Check the arm for some things unrelated to exhaustiveness.
             let arm = &self.thir.arms[arm];
-            self.check_patterns(&arm.pattern, Refutable);
+            self.with_lint_level(arm.lint_level, |this| {
+                this.check_patterns(&arm.pattern, Refutable);
+            });
         }
 
         let tarms: Vec<_> = arms

tests/ui/lint/lint-attr-everywhere-early.rs

@@ -134,6 +134,14 @@ fn expressions() {
         }
     }
 
+    match f {
+        #[deny(ellipsis_inclusive_range_patterns)]
+        Match{f1: 0...100} => {}
+        //~^ ERROR range patterns are deprecated
+        //~| WARNING this is accepted in the current edition
+        _ => {}
+    }
+
     // Statement Block
     {
         #![deny(unsafe_code)]

tests/ui/lint/lint-attr-everywhere-early.stderr

@@ -384,103 +384,117 @@ note: the lint level is defined here
 LL |         #[deny(while_true)]
    |                ^^^^^^^^^^
 
+error: `...` range patterns are deprecated
+  --> $DIR/lint-attr-everywhere-early.rs:139:20
+   |
+LL |         Match{f1: 0...100} => {}
+   |                    ^^^ help: use `..=` for an inclusive range
+   |
+   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
+note: the lint level is defined here
+  --> $DIR/lint-attr-everywhere-early.rs:138:16
+   |
+LL |         #[deny(ellipsis_inclusive_range_patterns)]
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:140:9
+  --> $DIR/lint-attr-everywhere-early.rs:148:9
    |
 LL |         unsafe {}
    |         ^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:139:17
+  --> $DIR/lint-attr-everywhere-early.rs:147:17
    |
 LL |         #![deny(unsafe_code)]
    |                 ^^^^^^^^^^^
 
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:144:9
+  --> $DIR/lint-attr-everywhere-early.rs:152:9
    |
 LL |         unsafe {}
    |         ^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:143:16
+  --> $DIR/lint-attr-everywhere-early.rs:151:16
    |
 LL |         #[deny(unsafe_code)]
    |                ^^^^^^^^^^^
 
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:149:5
+  --> $DIR/lint-attr-everywhere-early.rs:157:5
    |
 LL |     unsafe {};
    |     ^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:148:12
+  --> $DIR/lint-attr-everywhere-early.rs:156:12
    |
 LL |     #[deny(unsafe_code)]
    |            ^^^^^^^^^^^
 
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:151:27
+  --> $DIR/lint-attr-everywhere-early.rs:159:27
    |
 LL |     [#[deny(unsafe_code)] unsafe {123}];
    |                           ^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:151:13
+  --> $DIR/lint-attr-everywhere-early.rs:159:13
    |
 LL |     [#[deny(unsafe_code)] unsafe {123}];
    |             ^^^^^^^^^^^
 
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:152:27
+  --> $DIR/lint-attr-everywhere-early.rs:160:27
    |
 LL |     (#[deny(unsafe_code)] unsafe {123},);
    |                           ^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:152:13
+  --> $DIR/lint-attr-everywhere-early.rs:160:13
    |
 LL |     (#[deny(unsafe_code)] unsafe {123},);
    |             ^^^^^^^^^^^
 
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:154:31
+  --> $DIR/lint-attr-everywhere-early.rs:162:31
    |
 LL |     call(#[deny(unsafe_code)] unsafe {123});
    |                               ^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:154:17
+  --> $DIR/lint-attr-everywhere-early.rs:162:17
    |
 LL |     call(#[deny(unsafe_code)] unsafe {123});
    |                 ^^^^^^^^^^^
 
 error: usage of an `unsafe` block
-  --> $DIR/lint-attr-everywhere-early.rs:156:38
+  --> $DIR/lint-attr-everywhere-early.rs:164:38
    |
 LL |     TupleStruct(#[deny(unsafe_code)] unsafe {123});
    |                                      ^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:156:24
+  --> $DIR/lint-attr-everywhere-early.rs:164:24
    |
 LL |     TupleStruct(#[deny(unsafe_code)] unsafe {123});
    |                        ^^^^^^^^^^^
 
 error: `...` range patterns are deprecated
-  --> $DIR/lint-attr-everywhere-early.rs:167:18
+  --> $DIR/lint-attr-everywhere-early.rs:175:18
    |
 LL |             f1: 0...100,
    |                  ^^^ help: use `..=` for an inclusive range
    |
    = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 note: the lint level is defined here
-  --> $DIR/lint-attr-everywhere-early.rs:166:20
+  --> $DIR/lint-attr-everywhere-early.rs:174:20
    |
 LL |             #[deny(ellipsis_inclusive_range_patterns)]
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 36 previous errors
+error: aborting due to 37 previous errors
 

tests/ui/lint/lint-attr-everywhere-late.rs

@@ -162,6 +162,11 @@ fn expressions() {
         }
     }
 
+    match 123 {
+        #[deny(non_snake_case)]
+        ARM_VAR => {} //~ ERROR variable `ARM_VAR` should have a snake case name
+    }
+
     // Statement Block
     {
         #![deny(enum_intrinsics_non_enums)]