Rollup merge of rust-lang#149863 - estebank:issue-149861, r=mati865

Do not suggest moving expression out of for loop when hitting `break` from desugaring

Fix rust-lang#149861.

Author: JonathanBrouwer

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -4521,7 +4521,9 @@ struct BreakFinder {
 impl<'hir> Visitor<'hir> for BreakFinder {
     fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) {
         match ex.kind {
-            hir::ExprKind::Break(destination, _) => {
+            hir::ExprKind::Break(destination, _)
+                if !ex.span.is_desugaring(DesugaringKind::ForLoop) =>
+            {
                 self.found_breaks.push((destination, ex.span));
             }
             hir::ExprKind::Continue(destination) => {

tests/ui/ergonomic-clones/closure/spawn-thread.edition2018.stderr

@@ -12,16 +12,6 @@ LL | |             drop((x.0, x.1, x.2));
    | |                   --- use occurs due to use in closure
 LL | |         });
    | |_________- value moved here, in previous iteration of loop
-   |
-help: consider moving the expression out of the loop so it is only moved once
-   |
-LL ~     let mut value = std::thread::spawn(use || {
-LL +
-LL +             drop((x.0, x.1, x.2));
-LL +         });
-LL ~     for _ in 0..10 {
-LL ~         let handler = value;
-   |
 
 error: aborting due to 1 previous error
 

tests/ui/moves/arc-consumed-in-looped-closure.rs

@@ -0,0 +1,37 @@
+use std::thread;
+use std::sync::{Arc, Mutex, Condvar};
+use std::collections::VecDeque;
+
+type Job = Box<dyn FnOnce() + Send + 'static>;
+
+struct ThreadPool {
+    workers: Vec<thread::JoinHandle<()>>,
+    queue: Arc<()>,
+}
+
+impl ThreadPool {
+    fn execute<F>(&self, f: F)
+    where
+        F: FnOnce() + Send + 'static,
+    {
+        panic!()
+    }
+}
+
+fn main() {
+    let results = Arc::new(Mutex::new(Vec::new())); //~ NOTE move occurs because
+    let pool = ThreadPool {
+        workers: vec![],
+        queue: Arc::new(()),
+    };
+
+    for i in 0..20 { //~ NOTE inside of this loop
+        // let results = Arc::clone(&results); // Forgot this.
+        pool.execute(move || { //~ ERROR E0382
+            //~^ NOTE value moved into closure here, in previous iteration of loop
+            //~| HELP consider cloning the value before moving it into the closure
+            let mut r = results.lock().unwrap(); //~ NOTE use occurs due to use in closure
+            r.push(i);
+        });
+    }
+}

tests/ui/moves/arc-consumed-in-looped-closure.stderr

@@ -0,0 +1,27 @@
+error[E0382]: use of moved value: `results`
+  --> $DIR/arc-consumed-in-looped-closure.rs:30:22
+   |
+LL |     let results = Arc::new(Mutex::new(Vec::new()));
+   |         ------- move occurs because `results` has type `Arc<std::sync::Mutex<Vec<i32>>>`, which does not implement the `Copy` trait
+...
+LL |     for i in 0..20 {
+   |     -------------- inside of this loop
+LL |         // let results = Arc::clone(&results); // Forgot this.
+LL |         pool.execute(move || {
+   |                      ^^^^^^^ value moved into closure here, in previous iteration of loop
+...
+LL |             let mut r = results.lock().unwrap();
+   |                         ------- use occurs due to use in closure
+   |
+help: consider cloning the value before moving it into the closure
+   |
+LL ~         let value = results.clone();
+LL ~         pool.execute(move || {
+LL |
+LL |
+LL ~             let mut r = value.lock().unwrap();
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0382`.

tests/ui/moves/nested-loop-moved-value-wrong-continue.rs

@@ -7,8 +7,6 @@ fn foo() {
     //~^ NOTE this reinitialization might get skipped
     //~| NOTE move occurs because `foo` has type `String`
     //~| NOTE inside of this loop
-    //~| HELP consider moving the expression out of the loop
-    //~| NOTE in this expansion of desugaring of `for` loop
     //~| NOTE
     //~| NOTE
         baz.push(foo);
@@ -35,16 +33,14 @@ fn main() {
     //~| NOTE
         for bar in &bars {
         //~^ NOTE inside of this loop
-        //~| HELP consider moving the expression out of the loop
-        //~| NOTE in this expansion of desugaring of `for` loop
         //~| NOTE
             if foo == *bar {
                 baz.push(foo);
                 //~^ NOTE value moved here
                 //~| HELP consider cloning the value
                 continue;
                 //~^ NOTE verify that your loop breaking logic is correct
-                //~| NOTE this `continue` advances the loop at line 36
+                //~| NOTE this `continue` advances the loop at line 34
             }
         }
         qux.push(foo);

tests/ui/moves/nested-loop-moved-value-wrong-continue.stderr

@@ -1,5 +1,5 @@
 error[E0382]: use of moved value: `foo`
-  --> $DIR/nested-loop-moved-value-wrong-continue.rs:21:14
+  --> $DIR/nested-loop-moved-value-wrong-continue.rs:19:14
    |
 LL |     for foo in foos { for bar in &bars { if foo == *bar {
    |         ---           ---------------- inside of this loop
@@ -14,29 +14,20 @@ LL |     qux.push(foo);
    |              ^^^ value used here after move
    |
 note: verify that your loop breaking logic is correct
-  --> $DIR/nested-loop-moved-value-wrong-continue.rs:17:9
+  --> $DIR/nested-loop-moved-value-wrong-continue.rs:15:9
    |
 LL |     for foo in foos { for bar in &bars { if foo == *bar {
    |     ---------------   ----------------
 ...
 LL |         continue;
-   |         ^^^^^^^^ this `continue` advances the loop at $DIR/nested-loop-moved-value-wrong-continue.rs:6:23: 20:8
-help: consider moving the expression out of the loop so it is only moved once
-   |
-LL ~     for foo in foos { let mut value = baz.push(foo);
-LL ~     for bar in &bars { if foo == *bar {
-LL |
-...
-LL |
-LL ~         value;
-   |
+   |         ^^^^^^^^ this `continue` advances the loop at $DIR/nested-loop-moved-value-wrong-continue.rs:6:23: 18:8
 help: consider cloning the value if the performance cost is acceptable
    |
 LL |         baz.push(foo.clone());
    |                     ++++++++
 
 error[E0382]: use of moved value: `foo`
-  --> $DIR/nested-loop-moved-value-wrong-continue.rs:50:18
+  --> $DIR/nested-loop-moved-value-wrong-continue.rs:46:18
    |
 LL |     for foo in foos {
    |         ---
@@ -54,7 +45,7 @@ LL |         qux.push(foo);
    |                  ^^^ value used here after move
    |
 note: verify that your loop breaking logic is correct
-  --> $DIR/nested-loop-moved-value-wrong-continue.rs:45:17
+  --> $DIR/nested-loop-moved-value-wrong-continue.rs:41:17
    |
 LL |     for foo in foos {
    |     ---------------
@@ -63,16 +54,7 @@ LL |         for bar in &bars {
    |         ----------------
 ...
 LL |                 continue;
-   |                 ^^^^^^^^ this `continue` advances the loop at line 36
-help: consider moving the expression out of the loop so it is only moved once
-   |
-LL ~         let mut value = baz.push(foo);
-LL ~         for bar in &bars {
-LL |
-...
-LL |             if foo == *bar {
-LL ~                 value;
-   |
+   |                 ^^^^^^^^ this `continue` advances the loop at line 34
 help: consider cloning the value if the performance cost is acceptable
    |
 LL |                 baz.push(foo.clone());