Auto merge of #56113 - spastorino:erroneous-loop-diagnostic-in-nll, r…

…=pnkfelix

Erroneous loop diagnostic in nll

Closes #53773

r? @nikomatsakis

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

@@ -65,10 +65,7 @@ impl<'cx, 'gcx, 'tcx> UseFinder<'cx, 'gcx, 'tcx> {
 
                 None => {
                     if p.statement_index < block_data.statements.len() {
-                        queue.push_back(Location {
-                            statement_index: p.statement_index + 1,
-                            ..p
-                        });
+                        queue.push_back(p.successor_within_block());
                     } else {
                         queue.extend(
                             block_data

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

@@ -5,7 +5,7 @@ LL |     for &x in &vector {
    |               -------
    |               |
    |               immutable borrow occurs here
-   |               immutable borrow used here, in later iteration of loop
+   |               immutable borrow later used here
 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
-   |               immutable borrow used here, in later iteration of loop
+   |               immutable borrow later used here
 ...
 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); //[ast]~ ERROR cannot borrow
    |                ^^^ immutable borrow occurs here
 ...
 LL |     *x = box 5;
-   |     -- mutable borrow used here, in later iteration of loop
+   |     -- mutable borrow later used here
 
 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;
-   |         -------- mutable borrow used here, in later iteration of loop
+   |         -------- mutable borrow later used here
 LL |         borrow(&*v); //[ast]~ ERROR cannot borrow
    |                ^^^ immutable borrow occurs here
 ...

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
    |                    |
-   |                    first borrow used here, in later iteration of loop
+   |                    first borrow later used here
 ...
 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:15:30
    |
 LL |             1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
-   |                    ---- first borrow used here, in later iteration of loop
+   |                    ---- first borrow later used here
 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
    |                    |
-   |                    first borrow used here, in later iteration of loop
+   |                    first borrow later used here
 ...
 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:15:30
    |
 LL |             1 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
-   |                    ---- first borrow used here, in later iteration of loop
+   |                    ---- first borrow later used here
 LL |             //[mir]~^ ERROR [E0499]
 LL |             2 => { addr.push(&mut x); } //[ast]~ ERROR [E0499]
    |                              ^^^^^^ second mutable borrow occurs here

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();
-   |         ----------- first borrow used here, in later iteration of loop
+   |         ----------- first borrow later used here
 
 error: aborting due to 2 previous errors
 

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 |         acc += cnt2;
-   |         --- borrow used here, in later iteration of loop
+   |         --- borrow later used here
 ...
 LL |     }
    |     - `line` dropped here while still borrowed

src/test/ui/nll/issue-53773.rs

@@ -0,0 +1,49 @@
+#![feature(nll)]
+
+struct Archive;
+struct ArchiveIterator<'a> {
+    x: &'a Archive,
+}
+struct ArchiveChild<'a> {
+    x: &'a Archive,
+}
+
+struct A {
+    raw: &'static mut Archive,
+}
+struct Iter<'a> {
+    raw: &'a mut ArchiveIterator<'a>,
+}
+struct C<'a> {
+    raw: &'a mut ArchiveChild<'a>,
+}
+
+impl A {
+    pub fn iter(&self) -> Iter<'_> {
+        panic!()
+    }
+}
+impl Drop for A {
+    fn drop(&mut self) {}
+}
+impl<'a> Drop for C<'a> {
+    fn drop(&mut self) {}
+}
+
+impl<'a> Iterator for Iter<'a> {
+    type Item = C<'a>;
+    fn next(&mut self) -> Option<C<'a>> {
+        panic!()
+    }
+}
+
+fn error(archive: &A) {
+    let mut members: Vec<&mut ArchiveChild<'_>> = vec![];
+    for child in archive.iter() {
+        members.push(child.raw);
+        //~^ ERROR borrow may still be in use when destructor runs [E0713]
+    }
+    members.len();
+}
+
+fn main() {}

src/test/ui/nll/issue-53773.stderr

@@ -0,0 +1,16 @@
+error[E0713]: borrow may still be in use when destructor runs
+  --> $DIR/issue-53773.rs:43:22
+   |
+LL |         members.push(child.raw);
+   |                      ^^^^^^^^^
+LL |         //~^ ERROR borrow may still be in use when destructor runs [E0713]
+LL |     }
+   |     - here, drop of `child` needs exclusive access to `*child.raw`, because the type `C<'_>` implements the `Drop` trait
+LL |     members.len();
+   |     ------- borrow later used here
+   |
+   = note: consider using a `let` binding to create a longer lived value
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0713`.

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);
-   |                              ------- immutable borrow used here, in later iteration of loop
+   |                              ------- immutable borrow later used here
 
 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:11:13
    |
 LL |         let x = 1 + *p;
-   |                     -- borrow used here, in later iteration of loop
+   |                     -- borrow later used here
 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 later used here
 
 error[E0503]: cannot use `x` because it was mutably borrowed
   --> $DIR/regions-escape-loop-via-vec.rs:6:21
@@ -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 later used here
 
 error[E0597]: `z` does not live long enough
   --> $DIR/regions-escape-loop-via-vec.rs:7:17
    |
 LL |         _y.push(&mut z);
    |         --      ^^^^^^ borrowed value does not live long enough
    |         |
-   |         borrow used here, in later iteration of loop
+   |         borrow later used here
 ...
 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 later used here
 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
-   |              first borrow used here, in later iteration of loop
+   |              first borrow later used here
 LL |         xs.push(1) //~ ERROR cannot borrow `xs`
    |         ^^ second mutable borrow occurs here