Rollup merge of #128701 - veera-sivarajan:fix-128604, r=estebank

Don't Suggest Labeling `const` and `unsafe` Blocks

Fixes #128604

Previously, both anonymous constant blocks (E.g. The labeled block
inside `['_'; 'block: { break 'block 1 + 2; }]`) and inline const
blocks (E.g. `const { ... }`) were considered to be the same
kind of blocks. This caused the compiler to incorrectly suggest
labeling both the blocks when only anonymous constant blocks can be
labeled.

This PR adds an other enum variant to `Context` so that both the
blocks can be handled appropriately.

Also, adds some doc comments and removes unnecessary `&mut` in a
couple of places.

compiler/rustc_passes/src/loops.rs

@@ -19,17 +19,25 @@ use crate::errors::{
     OutsideLoopSuggestion, UnlabeledCfInWhileCondition, UnlabeledInLabeledBlock,
 };
 
+/// The context in which a block is encountered.
 #[derive(Clone, Copy, Debug, PartialEq)]
 enum Context {
     Normal,
     Fn,
     Loop(hir::LoopSource),
     Closure(Span),
-    Coroutine { coroutine_span: Span, kind: hir::CoroutineDesugaring, source: hir::CoroutineSource },
+    Coroutine {
+        coroutine_span: Span,
+        kind: hir::CoroutineDesugaring,
+        source: hir::CoroutineSource,
+    },
     UnlabeledBlock(Span),
     UnlabeledIfBlock(Span),
     LabeledBlock,
-    Constant,
+    /// E.g. The labeled block inside `['_'; 'block: { break 'block 1 + 2; }]`.
+    AnonConst,
+    /// E.g. `const { ... }`.
+    ConstBlock,
 }
 
 #[derive(Clone)]
@@ -90,11 +98,11 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
     }
 
     fn visit_anon_const(&mut self, c: &'hir hir::AnonConst) {
-        self.with_context(Constant, |v| intravisit::walk_anon_const(v, c));
+        self.with_context(AnonConst, |v| intravisit::walk_anon_const(v, c));
     }
 
     fn visit_inline_const(&mut self, c: &'hir hir::ConstBlock) {
-        self.with_context(Constant, |v| intravisit::walk_inline_const(v, c));
+        self.with_context(ConstBlock, |v| intravisit::walk_inline_const(v, c));
     }
 
     fn visit_fn(
@@ -128,7 +136,7 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
                         && matches!(
                             ck_loop.cx_stack.last(),
                             Some(&Normal)
-                                | Some(&Constant)
+                                | Some(&AnonConst)
                                 | Some(&UnlabeledBlock(_))
                                 | Some(&UnlabeledIfBlock(_))
                         )
@@ -175,14 +183,18 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
             hir::ExprKind::Block(ref b, Some(_label)) => {
                 self.with_context(LabeledBlock, |v| v.visit_block(b));
             }
-            hir::ExprKind::Block(ref b, None) if matches!(self.cx_stack.last(), Some(&Fn)) => {
+            hir::ExprKind::Block(ref b, None)
+                if matches!(self.cx_stack.last(), Some(&Fn) | Some(&ConstBlock)) =>
+            {
                 self.with_context(Normal, |v| v.visit_block(b));
             }
-            hir::ExprKind::Block(ref b, None)
-                if matches!(
-                    self.cx_stack.last(),
-                    Some(&Normal) | Some(&Constant) | Some(&UnlabeledBlock(_))
-                ) =>
+            hir::ExprKind::Block(
+                ref b @ hir::Block { rules: hir::BlockCheckMode::DefaultBlock, .. },
+                None,
+            ) if matches!(
+                self.cx_stack.last(),
+                Some(&Normal) | Some(&AnonConst) | Some(&UnlabeledBlock(_))
+            ) =>
             {
                 self.with_context(UnlabeledBlock(b.span.shrink_to_lo()), |v| v.visit_block(b));
             }
@@ -353,7 +365,7 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
             UnlabeledIfBlock(_) if br_cx_kind == BreakContextKind::Break => {
                 self.require_break_cx(br_cx_kind, span, break_span, cx_pos - 1);
             }
-            Normal | Constant | Fn | UnlabeledBlock(_) | UnlabeledIfBlock(_) => {
+            Normal | AnonConst | Fn | UnlabeledBlock(_) | UnlabeledIfBlock(_) | ConstBlock => {
                 self.sess.dcx().emit_err(OutsideLoop {
                     spans: vec![span],
                     name: &br_cx_kind.to_string(),
@@ -365,7 +377,7 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
     }
 
     fn require_label_in_labeled_block(
-        &mut self,
+        &self,
         span: Span,
         label: &Destination,
         cf_type: &str,
@@ -380,7 +392,7 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
         false
     }
 
-    fn report_outside_loop_error(&mut self) {
+    fn report_outside_loop_error(&self) {
         for (s, block) in &self.block_breaks {
             self.sess.dcx().emit_err(OutsideLoop {
                 spans: block.spans.clone(),

tests/ui/inline-const/break-inside-inline-const-issue-128604.rs

@@ -0,0 +1,25 @@
+fn main() {
+    let _ = ['a'; { break 2; 1 }];
+    //~^ ERROR `break` outside of a loop or labeled block
+    //~| HELP consider labeling this block to be able to break within it
+
+    const {
+        {
+            //~^ HELP consider labeling this block to be able to break within it
+            break;
+            //~^ ERROR `break` outside of a loop or labeled block
+        }
+    };
+
+    const {
+        break;
+        //~^ ERROR `break` outside of a loop or labeled block
+    };
+
+    {
+        const {
+            break;
+            //~^ ERROR `break` outside of a loop or labeled block
+        }
+    }
+}

tests/ui/inline-const/break-inside-inline-const-issue-128604.stderr

@@ -0,0 +1,39 @@
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-inline-const-issue-128604.rs:15:9
+   |
+LL |         break;
+   |         ^^^^^ cannot `break` outside of a loop or labeled block
+
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-inline-const-issue-128604.rs:21:13
+   |
+LL |             break;
+   |             ^^^^^ cannot `break` outside of a loop or labeled block
+
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-inline-const-issue-128604.rs:2:21
+   |
+LL |     let _ = ['a'; { break 2; 1 }];
+   |                     ^^^^^^^ cannot `break` outside of a loop or labeled block
+   |
+help: consider labeling this block to be able to break within it
+   |
+LL |     let _ = ['a'; 'block: { break 'block 2; 1 }];
+   |                   +++++++         ++++++
+
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-inline-const-issue-128604.rs:9:13
+   |
+LL |             break;
+   |             ^^^^^ cannot `break` outside of a loop or labeled block
+   |
+help: consider labeling this block to be able to break within it
+   |
+LL ~         'block: {
+LL |
+LL ~             break 'block;
+   |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0268`.

tests/ui/unsafe/break-inside-unsafe-block-issue-128604.rs

@@ -0,0 +1,34 @@
+fn main() {
+    let a = ["_"; unsafe { break; 1 + 2 }];
+    //~^ ERROR `break` outside of a loop or labeled block
+
+    unsafe {
+        {
+            //~^ HELP consider labeling this block to be able to break within it
+            break;
+            //~^ ERROR `break` outside of a loop or labeled block
+        }
+    }
+
+    unsafe {
+        break;
+        //~^ ERROR `break` outside of a loop or labeled block
+    }
+
+    {
+        //~^ HELP consider labeling this block to be able to break within it
+        unsafe {
+            break;
+            //~^ ERROR `break` outside of a loop or labeled block
+        }
+    }
+
+    while 2 > 1 {
+        unsafe {
+            if true || false {
+                break;
+            }
+        }
+    }
+
+}

tests/ui/unsafe/break-inside-unsafe-block-issue-128604.stderr

@@ -0,0 +1,42 @@
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-unsafe-block-issue-128604.rs:2:28
+   |
+LL |     let a = ["_"; unsafe { break; 1 + 2 }];
+   |                            ^^^^^ cannot `break` outside of a loop or labeled block
+
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-unsafe-block-issue-128604.rs:14:9
+   |
+LL |         break;
+   |         ^^^^^ cannot `break` outside of a loop or labeled block
+
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-unsafe-block-issue-128604.rs:8:13
+   |
+LL |             break;
+   |             ^^^^^ cannot `break` outside of a loop or labeled block
+   |
+help: consider labeling this block to be able to break within it
+   |
+LL ~         'block: {
+LL |
+LL ~             break 'block;
+   |
+
+error[E0268]: `break` outside of a loop or labeled block
+  --> $DIR/break-inside-unsafe-block-issue-128604.rs:21:13
+   |
+LL |             break;
+   |             ^^^^^ cannot `break` outside of a loop or labeled block
+   |
+help: consider labeling this block to be able to break within it
+   |
+LL ~     'block: {
+LL |
+LL |         unsafe {
+LL ~             break 'block;
+   |
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0268`.