NLL: Improve move error loop detection (was "First shot at #54015")

src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs

@@ -46,9 +46,9 @@ impl<'tcx> BorrowExplanation<'tcx> {
             },
             BorrowExplanation::UsedLaterInLoop(is_in_closure, var_or_use_span) => {
                 let message = if is_in_closure {
-                    "borrow captured here by closure in later iteration of loop"
+                    "borrow captured here by closure, in later iteration of loop"
                 } else {
-                    "borrow used here in later iteration of loop"
+                    "borrow used here, in later iteration of loop"
                 };
                 err.span_label(var_or_use_span, message);
             },

src/test/ui/borrowck/borrowck-for-loop-head-linkage.nll.stderr

@@ -5,7 +5,7 @@ LL |     for &x in &vector {
    |               -------
    |               |
    |               immutable borrow occurs here
-   |               borrow used here in later iteration of loop
+   |               borrow used here, in later iteration of loop
 LL |         let cap = vector.capacity();
 LL |         vector.extend(repeat(0));      //~ ERROR cannot borrow
    |         ^^^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here
@@ -17,7 +17,7 @@ LL |     for &x in &vector {
    |               -------
    |               |
    |               immutable borrow occurs here
-   |               borrow used here in later iteration of loop
+   |               borrow used here, in later iteration of loop
 ...
 LL |         vector[1] = 5;   //~ ERROR cannot borrow
    |         ^^^^^^ mutable borrow occurs here

src/test/ui/borrowck/borrowck-lend-flow-loop.nll.stderr

@@ -8,13 +8,13 @@ LL |         borrow(&*v); //~ ERROR cannot borrow
    |                ^^^ immutable borrow occurs here
 LL |     }
 LL |     *x = box 5;
-   |     -- borrow used here in later iteration of loop
+   |     -- borrow used here, in later iteration of loop
 
 error[E0502]: cannot borrow `*v` as immutable because it is also borrowed as mutable
   --> $DIR/borrowck-lend-flow-loop.rs:109:16
    |
 LL |         **x += 1;
-   |         -------- borrow used here in later iteration of loop
+   |         -------- borrow used here, in later iteration of loop
 LL |         borrow(&*v); //~ ERROR cannot borrow
    |                ^^^ immutable borrow occurs here
 LL |         if cond2 {

src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.ast.nll.stderr

@@ -4,7 +4,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time
 LL |             1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                    ----      ^^^^^^ second mutable borrow occurs here
    |                    |
-   |                    borrow used here in later iteration of loop
+   |                    borrow used here, in later iteration of loop
 ...
 LL |             _ => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                              ------ first mutable borrow occurs here
@@ -13,7 +13,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time
   --> $DIR/borrowck-mut-borrow-linear-errors.rs:25:30
    |
 LL |             1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
-   |                    ---- borrow used here in later iteration of loop
+   |                    ---- borrow used here, in later iteration of loop
 LL |             //[mir]~^ ERROR [E0499]
 LL |             2 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                              ^^^^^^ second mutable borrow occurs here

src/test/ui/borrowck/borrowck-mut-borrow-linear-errors.mir.stderr

@@ -4,7 +4,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time
 LL |             1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                    ----      ^^^^^^ second mutable borrow occurs here
    |                    |
-   |                    borrow used here in later iteration of loop
+   |                    borrow used here, in later iteration of loop
 ...
 LL |             _ => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                              ------ first mutable borrow occurs here
@@ -13,7 +13,7 @@ error[E0499]: cannot borrow `x` as mutable more than once at a time
   --> $DIR/borrowck-mut-borrow-linear-errors.rs:25:30
    |
 LL |             1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
-   |                    ---- borrow used here in later iteration of loop
+   |                    ---- borrow used here, in later iteration of loop
 LL |             //[mir]~^ ERROR [E0499]
 LL |             2 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                              ^^^^^^ second mutable borrow occurs here

src/test/ui/borrowck/issue-41962.stderr

@@ -20,7 +20,7 @@ error[E0382]: use of moved value (Mir)
   --> $DIR/issue-41962.rs:17:21
    |
 LL |         if let Some(thing) = maybe {
-   |                     ^^^^^ value moved here in previous iteration of loop
+   |                     ^^^^^ value moved here, in previous iteration of loop
    |
    = note: move occurs because value has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait
 

src/test/ui/borrowck/mut-borrow-outside-loop.nll.stderr

@@ -17,7 +17,7 @@ LL |         let inner_second = &mut inner_void; //~ ERROR cannot borrow
    |                            ^^^^^^^^^^^^^^^ second mutable borrow occurs here
 LL |         inner_second.use_mut();
 LL |         inner_first.use_mut();
-   |         ----------- borrow used here in later iteration of loop
+   |         ----------- borrow used here, in later iteration of loop
 
 error: aborting due to 2 previous errors
 

src/test/ui/issues/issue-12041.nll.stderr

@@ -2,7 +2,7 @@ error[E0382]: use of moved value: `tx`
   --> $DIR/issue-12041.rs:18:22
    |
 LL |             let tx = tx;
-   |                      ^^ value moved here in previous iteration of loop
+   |                      ^^ value moved here, in previous iteration of loop
    |
    = note: move occurs because `tx` has type `std::sync::mpsc::Sender<i32>`, which does not implement the `Copy` trait
 

src/test/ui/issues/issue-52126-assign-op-invariance.nll.stderr

@@ -5,7 +5,7 @@ LL |         let v: Vec<&str> = line.split_whitespace().collect();
    |                            ^^^^ borrowed value does not live long enough
 LL |         //~^ ERROR `line` does not live long enough
 LL |         println!("accumulator before add_assign {:?}", acc.map);
-   |                                                        ------- borrow used here in later iteration of loop
+   |                                                        ------- borrow used here, in later iteration of loop
 ...
 LL |     }
    |     - `line` dropped here while still borrowed

src/test/ui/liveness/liveness-move-call-arg.nll.stderr

@@ -0,0 +1,11 @@
+error[E0382]: use of moved value: `x`
+  --> $DIR/liveness-move-call-arg.rs:19:14
+   |
+LL |         take(x); //~ ERROR use of moved value: `x`
+   |              ^ value moved here, in previous iteration of loop
+   |
+   = note: move occurs because `x` has type `std::boxed::Box<isize>`, which does not implement the `Copy` trait
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.

src/test/ui/liveness/liveness-move-in-loop.nll.stderr

@@ -0,0 +1,11 @@
+error[E0382]: use of moved value: `y`
+  --> $DIR/liveness-move-in-loop.rs:21:25
+   |
+LL |                     x = y; //~ ERROR use of moved value
+   |                         ^ value moved here, in previous iteration of loop
+   |
+   = note: move occurs because `y` has type `std::boxed::Box<isize>`, which does not implement the `Copy` trait
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.

src/test/ui/liveness/liveness-move-in-while.nll.stderr

@@ -4,7 +4,7 @@ error[E0382]: borrow of moved value: `y`
 LL |         println!("{}", y); //~ ERROR use of moved value: `y`
    |                        ^ value borrowed here after move
 LL |         while true { while true { while true { x = y; x.clone(); } } }
-   |                                                    - value moved here
+   |                                                    - value moved here, in previous iteration of loop
    |
    = note: move occurs because `y` has type `std::boxed::Box<isize>`, which does not implement the `Copy` trait
 

src/test/ui/moves/move-in-guard-2.nll.stderr

@@ -0,0 +1,11 @@
+error[E0382]: use of moved value: `x`
+  --> $DIR/move-in-guard-2.rs:20:24
+   |
+LL |         (_, 2) if take(x) => (), //~ ERROR use of moved value: `x`
+   |                        ^ value moved here, in previous iteration of loop
+   |
+   = note: move occurs because `x` has type `std::boxed::Box<i32>`, which does not implement the `Copy` trait
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.

src/test/ui/nll/closures-in-loops.stderr

@@ -4,7 +4,7 @@ error[E0382]: use of moved value: `x`
 LL |         || x; //~ ERROR
    |         ^^ - use occurs due to use in closure
    |         |
-   |         value moved into closure here in previous iteration of loop
+   |         value moved into closure here, in previous iteration of loop
    |
    = note: move occurs because `x` has type `std::string::String`, which does not implement the `Copy` trait
 

src/test/ui/nll/issue-53807.nll.stderr

@@ -2,7 +2,7 @@ error[E0382]: use of moved value
   --> $DIR/issue-53807.rs:14:21
    |
 LL |         if let Some(thing) = maybe {
-   |                     ^^^^^ value moved here in previous iteration of loop
+   |                     ^^^^^ value moved here, in previous iteration of loop
    |
    = note: move occurs because value has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait
 

src/test/ui/rfc-2005-default-binding-mode/borrowck-issue-49631.nll.stderr

@@ -7,7 +7,7 @@ LL |         foo.mutate();
    |         ^^^^^^^^^^^^ mutable borrow occurs here
 LL |         //~^ ERROR cannot borrow `foo` as mutable
 LL |         println!("foo={:?}", *string);
-   |                              ------- borrow used here in later iteration of loop
+   |                              ------- borrow used here, in later iteration of loop
 
 error: aborting due to previous error
 

src/test/ui/span/regions-escape-loop-via-variable.nll.stderr

@@ -2,7 +2,7 @@ error[E0597]: `x` does not live long enough
   --> $DIR/regions-escape-loop-via-variable.rs:21:13
    |
 LL |         let x = 1 + *p;
-   |                     -- borrow used here in later iteration of loop
+   |                     -- borrow used here, in later iteration of loop
 LL |         p = &x;
    |             ^^ borrowed value does not live long enough
 LL |     }

src/test/ui/span/regions-escape-loop-via-vec.nll.stderr

@@ -7,7 +7,7 @@ LL |     while x < 10 { //~ ERROR cannot use `x` because it was mutably borrowed
    |           ^ use of borrowed `x`
 LL |         let mut z = x; //~ ERROR cannot use `x` because it was mutably borrowed
 LL |         _y.push(&mut z);
-   |         -- borrow used here in later iteration of loop
+   |         -- borrow used here, in later iteration of loop
 
 error[E0503]: cannot use `x` because it was mutably borrowed
   --> $DIR/regions-escape-loop-via-vec.rs:16:21
@@ -18,15 +18,15 @@ LL |     while x < 10 { //~ ERROR cannot use `x` because it was mutably borrowed
 LL |         let mut z = x; //~ ERROR cannot use `x` because it was mutably borrowed
    |                     ^ use of borrowed `x`
 LL |         _y.push(&mut z);
-   |         -- borrow used here in later iteration of loop
+   |         -- borrow used here, in later iteration of loop
 
 error[E0597]: `z` does not live long enough
   --> $DIR/regions-escape-loop-via-vec.rs:17:17
    |
 LL |         _y.push(&mut z);
    |         --      ^^^^^^ borrowed value does not live long enough
    |         |
-   |         borrow used here in later iteration of loop
+   |         borrow used here, in later iteration of loop
 ...
 LL |     }
    |     - `z` dropped here while still borrowed
@@ -38,7 +38,7 @@ LL |     let mut _y = vec![&mut x];
    |                       ------ borrow of `x` occurs here
 ...
 LL |         _y.push(&mut z);
-   |         -- borrow used here in later iteration of loop
+   |         -- borrow used here, in later iteration of loop
 LL |         //~^ ERROR `z` does not live long enough
 LL |         x += 1; //~ ERROR cannot assign
    |         ^^^^^^ use of borrowed `x`

src/test/ui/vec/vec-mut-iter-borrow.nll.stderr

@@ -5,7 +5,7 @@ LL |     for x in &mut xs {
    |              -------
    |              |
    |              first mutable borrow occurs here
-   |              borrow used here in later iteration of loop
+   |              borrow used here, in later iteration of loop
 LL |         xs.push(1) //~ ERROR cannot borrow `xs`
    |         ^^ second mutable borrow occurs here