Check for shadowing issues involving block labels

Author: tmiasko

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -1652,7 +1652,11 @@ fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body<'_>) {
     }
 
     fn expression_label(ex: &hir::Expr<'_>) -> Option<Ident> {
-        if let hir::ExprKind::Loop(_, Some(label), ..) = ex.kind { Some(label.ident) } else { None }
+        match ex.kind {
+            hir::ExprKind::Loop(_, Some(label), ..) => Some(label.ident),
+            hir::ExprKind::Block(_, Some(label)) => Some(label.ident),
+            _ => None,
+        }
     }
 
     fn check_if_label_shadows_lifetime(tcx: TyCtxt<'_>, mut scope: ScopeRef<'_>, label: Ident) {

src/test/ui/loops/loops-reject-duplicate-labels-2.rs

@@ -1,7 +1,7 @@
 // check-pass
+#![feature(label_break_value)]
 
-
-// Issue #21633: reject duplicate loop labels in function bodies.
+// Issue #21633: reject duplicate loop labels and block labels in function bodies.
 //
 // This is testing the generalization (to the whole function body)
 // discussed here:
@@ -26,6 +26,8 @@ pub fn foo() {
     { 'lt: loop { break; } }
     { 'lt: while let Some(_) = None::<i32> { break; } }
                                          //~^ WARN label name `'lt` shadows a label name that is already in scope
+    { 'bl: {} }
+    { 'bl: {} } //~ WARN label name `'bl` shadows a label name that is already in scope
 }
 
 

src/test/ui/loops/loops-reject-duplicate-labels-2.stderr

@@ -62,5 +62,13 @@ LL |     { 'lt: loop { break; } }
 LL |     { 'lt: while let Some(_) = None::<i32> { break; } }
    |       ^^^ label `'lt` already in scope
 
-warning: 8 warnings emitted
+warning: label name `'bl` shadows a label name that is already in scope
+  --> $DIR/loops-reject-duplicate-labels-2.rs:30:7
+   |
+LL |     { 'bl: {} }
+   |       --- first declared here
+LL |     { 'bl: {} }
+   |       ^^^ label `'bl` already in scope
+
+warning: 9 warnings emitted
 

src/test/ui/loops/loops-reject-duplicate-labels.rs

@@ -1,8 +1,7 @@
 // check-pass
+#![feature(label_break_value)]
 
-
-// Issue #21633: reject duplicate loop labels in function bodies.
-// This is testing the exact cases that are in the issue description.
+// Issue #21633: reject duplicate loop labels and block labels in function bodies.
 
 #[allow(unused_labels)]
 fn foo() {
@@ -24,6 +23,8 @@ fn foo() {
     'lt: loop { break; }
     'lt: while let Some(_) = None::<i32> { break; }
                                    //~^ WARN label name `'lt` shadows a label name that is already in scope
+    'bl: {}
+    'bl: {} //~ WARN label name `'bl` shadows a label name that is already in scope
 }
 
 // Note however that it is okay for the same label to be reused in
@@ -33,12 +34,16 @@ struct S;
 impl S {
     fn m1(&self) { 'okay: loop { break 'okay; } }
     fn m2(&self) { 'okay: loop { break 'okay; } }
+    fn m3(&self) { 'okay: { break 'okay; } }
+    fn m4(&self) { 'okay: { break 'okay; } }
 }
 
 
 pub fn main() {
     let s = S;
     s.m1();
     s.m2();
+    s.m3();
+    s.m4();
     foo();
 }

src/test/ui/loops/loops-reject-duplicate-labels.stderr

@@ -1,66 +1,74 @@
 warning: label name `'fl` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:10:5
+  --> $DIR/loops-reject-duplicate-labels.rs:9:5
    |
 LL |     'fl: for _ in 0..10 { break; }
    |     --- first declared here
 LL |     'fl: loop { break; }
    |     ^^^ label `'fl` already in scope
 
 warning: label name `'lf` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:13:5
+  --> $DIR/loops-reject-duplicate-labels.rs:12:5
    |
 LL |     'lf: loop { break; }
    |     --- first declared here
 LL |     'lf: for _ in 0..10 { break; }
    |     ^^^ label `'lf` already in scope
 
 warning: label name `'wl` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:15:5
+  --> $DIR/loops-reject-duplicate-labels.rs:14:5
    |
 LL |     'wl: while 2 > 1 { break; }
    |     --- first declared here
 LL |     'wl: loop { break; }
    |     ^^^ label `'wl` already in scope
 
 warning: label name `'lw` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:17:5
+  --> $DIR/loops-reject-duplicate-labels.rs:16:5
    |
 LL |     'lw: loop { break; }
    |     --- first declared here
 LL |     'lw: while 2 > 1 { break; }
    |     ^^^ label `'lw` already in scope
 
 warning: label name `'fw` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:19:5
+  --> $DIR/loops-reject-duplicate-labels.rs:18:5
    |
 LL |     'fw: for _ in 0..10 { break; }
    |     --- first declared here
 LL |     'fw: while 2 > 1 { break; }
    |     ^^^ label `'fw` already in scope
 
 warning: label name `'wf` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:21:5
+  --> $DIR/loops-reject-duplicate-labels.rs:20:5
    |
 LL |     'wf: while 2 > 1 { break; }
    |     --- first declared here
 LL |     'wf: for _ in 0..10 { break; }
    |     ^^^ label `'wf` already in scope
 
 warning: label name `'tl` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:23:5
+  --> $DIR/loops-reject-duplicate-labels.rs:22:5
    |
 LL |     'tl: while let Some(_) = None::<i32> { break; }
    |     --- first declared here
 LL |     'tl: loop { break; }
    |     ^^^ label `'tl` already in scope
 
 warning: label name `'lt` shadows a label name that is already in scope
-  --> $DIR/loops-reject-duplicate-labels.rs:25:5
+  --> $DIR/loops-reject-duplicate-labels.rs:24:5
    |
 LL |     'lt: loop { break; }
    |     --- first declared here
 LL |     'lt: while let Some(_) = None::<i32> { break; }
    |     ^^^ label `'lt` already in scope
 
-warning: 8 warnings emitted
+warning: label name `'bl` shadows a label name that is already in scope
+  --> $DIR/loops-reject-duplicate-labels.rs:27:5
+   |
+LL |     'bl: {}
+   |     --- first declared here
+LL |     'bl: {}
+   |     ^^^ label `'bl` already in scope
+
+warning: 9 warnings emitted
 

src/test/ui/loops/loops-reject-lifetime-shadowing-label.rs

@@ -1,10 +1,10 @@
 // check-pass
-
+#![feature(label_break_value)]
 #![allow(dead_code, unused_variables)]
 
-// Issue #21633:  reject duplicate loop labels in function bodies.
+// Issue #21633:  reject duplicate loop labels and block labels in function bodies.
 //
-// Test rejection of lifetimes in *expressions* that shadow loop labels.
+// Test rejection of lifetimes in *expressions* that shadow labels.
 
 fn foo() {
     // Reusing lifetime `'a` in function item is okay.
@@ -23,8 +23,13 @@ fn foo() {
         assert_eq!((*b)(&z), z);
         break 'a;
     }
-}
 
+    'b: {
+        let b = Box::new(|x: &()| ()) as Box<dyn for <'b> Fn(&'b ())>;
+        //~^ WARN lifetime name `'b` shadows a label name that is already in scope
+        break 'b;
+    }
+}
 
 pub fn main() {
     foo();

src/test/ui/loops/loops-reject-lifetime-shadowing-label.stderr

@@ -6,5 +6,13 @@ LL |     'a: loop {
 LL |         let b = Box::new(|x: &i8| *x) as Box<dyn for <'a> Fn(&'a i8) -> i8>;
    |                                                       ^^ label `'a` already in scope
 
-warning: 1 warning emitted
+warning: lifetime name `'b` shadows a label name that is already in scope
+  --> $DIR/loops-reject-lifetime-shadowing-label.rs:28:55
+   |
+LL |     'b: {
+   |     -- first declared here
+LL |         let b = Box::new(|x: &()| ()) as Box<dyn for <'b> Fn(&'b ())>;
+   |                                                       ^^ label `'b` already in scope
+
+warning: 2 warnings emitted