Don't emit cannot move errors twice in migrate mode

Author: matthewjasper

src/librustc_mir/borrow_check/mod.rs

@@ -1831,7 +1831,10 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             | Write(wk @ WriteKind::StorageDeadOrDrop)
             | Write(wk @ WriteKind::MutableBorrow(BorrowKind::Shared))
             | Write(wk @ WriteKind::MutableBorrow(BorrowKind::Shallow)) => {
-                if let Err(_place_err) = self.is_mutable(place, is_local_mutation_allowed) {
+                if let (Err(_place_err), true) = (
+                    self.is_mutable(place, is_local_mutation_allowed),
+                    self.errors_buffer.is_empty()
+                ) {
                     if self.infcx.tcx.migrate_borrowck() {
                         // rust-lang/rust#46908: In pure NLL mode this
                         // code path should be unreachable (and thus
@@ -1855,12 +1858,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                             location,
                         );
                     } else {
-                        self.infcx.tcx.sess.delay_span_bug(
+                        span_bug!(
                             span,
-                            &format!(
-                                "Accessing `{:?}` with the kind `{:?}` shouldn't be possible",
-                                place, kind
-                            ),
+                            "Accessing `{:?}` with the kind `{:?}` shouldn't be possible",
+                            place,
+                            kind,
                         );
                     }
                 }

src/librustc_mir/borrow_check/mutability_errors.rs

@@ -180,9 +180,9 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
             AccessKind::Move => {
                 err = self.infcx.tcx
                     .cannot_move_out_of(span, &(item_msg + &reason), Origin::Mir);
-                act = "move";
-                acted_on = "moved";
-                span
+                err.span_label(span, "cannot move");
+                err.buffer(&mut self.errors_buffer);
+                return;
             }
             AccessKind::Mutate => {
                 err = self.infcx.tcx

src/test/ui/access-mode-in-closures.nll.stderr

@@ -13,18 +13,6 @@ note: move occurs because `v` has type `std::vec::Vec<isize>`, which does not im
 LL |         match *s { sty(v) => v } //~ ERROR cannot move out
    |                        ^
 
-error[E0507]: cannot move out of `s.0` which is behind a `&` reference
-  --> $DIR/access-mode-in-closures.rs:19:24
-   |
-LL |     let _foo = unpack(|s| {
-   |                        - help: consider changing this to be a mutable reference: `&mut sty`
-LL |         // Test that `s` is moved here.
-LL |         match *s { sty(v) => v } //~ ERROR cannot move out
-   |                        ^
-   |                        |
-   |                        cannot move out of `s.0` which is behind a `&` reference
-   |                        `s` is a `&` reference, so the data it refers to cannot be moved
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0507`.

src/test/ui/binop/binop-move-semantics.nll.stderr

@@ -32,18 +32,6 @@ error[E0507]: cannot move out of borrowed content
 LL |     *n;  //~ ERROR: cannot move out of borrowed content
    |     ^^ cannot move out of borrowed content
 
-error[E0507]: cannot move out of `*n` which is behind a `&` reference
-  --> $DIR/binop-move-semantics.rs:42:5
-   |
-LL |     let n = &y;
-   |             -- help: consider changing this to be a mutable reference: `&mut y`
-...
-LL |     *n;  //~ ERROR: cannot move out of borrowed content
-   |     ^^
-   |     |
-   |     cannot move out of `*n` which is behind a `&` reference
-   |     `n` is a `&` reference, so the data it refers to cannot be moved
-
 error[E0502]: cannot borrow `f` as immutable because it is also borrowed as mutable
   --> $DIR/binop-move-semantics.rs:64:5
    |
@@ -74,7 +62,7 @@ LL | |     &mut f;  //~ ERROR: cannot borrow `f` as mutable because it is also b
    |       |    immutable borrow later used here
    |       mutable borrow occurs here
 
-error: aborting due to 7 previous errors
+error: aborting due to 6 previous errors
 
 Some errors occurred: E0382, E0502, E0507.
 For more information about an error, try `rustc --explain E0382`.

src/test/ui/borrowck/borrowck-fn-in-const-a.ast.nll.stderr

@@ -1,13 +1,3 @@
-error[E0507]: cannot move out of `*__next` which is behind a `&` reference
-  --> $DIR/borrowck-for-loop-correct-cmt-for-pattern.rs:22:10
-   |
-LL |     for &a in x.iter() {    //~ ERROR cannot move out
-   |         -^
-   |         ||
-   |         |cannot move out of `*__next` which is behind a `&` reference
-   |         |`__next` is a `&` reference, so the data it refers to cannot be moved
-   |         help: consider changing this to be a mutable reference: `&mut a`
-
 error[E0507]: cannot move out of borrowed content
   --> $DIR/borrowck-for-loop-correct-cmt-for-pattern.rs:22:15
    |
@@ -23,16 +13,6 @@ note: move occurs because `a` has type `&mut i32`, which does not implement the
 LL |     for &a in x.iter() {    //~ ERROR cannot move out
    |          ^
 
-error[E0507]: cannot move out of `*__next` which is behind a `&` reference
-  --> $DIR/borrowck-for-loop-correct-cmt-for-pattern.rs:28:10
-   |
-LL |     for &a in &f.a {  //~ ERROR cannot move out
-   |         -^
-   |         ||
-   |         |cannot move out of `*__next` which is behind a `&` reference
-   |         |`__next` is a `&` reference, so the data it refers to cannot be moved
-   |         help: consider changing this to be a mutable reference: `&mut a`
-
 error[E0507]: cannot move out of borrowed content
   --> $DIR/borrowck-for-loop-correct-cmt-for-pattern.rs:28:15
    |
@@ -48,16 +28,6 @@ note: move occurs because `a` has type `std::boxed::Box<isize>`, which does not
 LL |     for &a in &f.a {  //~ ERROR cannot move out
    |          ^
 
-error[E0507]: cannot move out of `*__next` which is behind a `&` reference
-  --> $DIR/borrowck-for-loop-correct-cmt-for-pattern.rs:32:10
-   |
-LL |     for &a in x.iter() {    //~ ERROR cannot move out
-   |         -^
-   |         ||
-   |         |cannot move out of `*__next` which is behind a `&` reference
-   |         |`__next` is a `&` reference, so the data it refers to cannot be moved
-   |         help: consider changing this to be a mutable reference: `&mut a`
-
 error[E0507]: cannot move out of borrowed content
   --> $DIR/borrowck-for-loop-correct-cmt-for-pattern.rs:32:15
    |
@@ -73,6 +43,6 @@ note: move occurs because `a` has type `std::boxed::Box<i32>`, which does not im
 LL |     for &a in x.iter() {    //~ ERROR cannot move out
    |          ^
 
-error: aborting due to 6 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0507`.

src/test/ui/borrowck/borrowck-for-loop-correct-cmt-for-pattern.nll.stderr

@@ -6,21 +6,6 @@ LL |     let x = Box::new(0);
 LL |     Box::new(|| x) //~ ERROR cannot move out of captured outer variable
    |                 ^ cannot move out of captured variable in an `Fn` closure
 
-error[E0507]: cannot move out of `x`, as it is a captured variable in a `Fn` closure
-  --> $DIR/borrowck-in-static.rs:15:17
-   |
-LL |     Box::new(|| x) //~ ERROR cannot move out of captured outer variable
-   |                 ^
-   |                 |
-   |                 cannot move out of `x`, as it is a captured variable in a `Fn` closure
-   |                 cannot move
-   |
-help: consider changing this to accept closures that implement `FnMut`
-  --> $DIR/borrowck-in-static.rs:15:14
-   |
-LL |     Box::new(|| x) //~ ERROR cannot move out of captured outer variable
-   |              ^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0507`.

src/test/ui/borrowck/borrowck-in-static.nll.stderr

@@ -7,17 +7,6 @@ LL |         let _b = *y; //~ ERROR cannot move out
    |                  cannot move out of borrowed content
    |                  help: consider removing the `*`: `y`
 
-error[E0507]: cannot move out of `*y` which is behind a `&` reference
-  --> $DIR/borrowck-issue-2657-2.rs:17:18
-   |
-LL |       Some(ref y) => {
-   |            ----- help: consider changing this to be a mutable reference: `ref mut y`
-LL |         let _b = *y; //~ ERROR cannot move out
-   |                  ^^
-   |                  |
-   |                  cannot move out of `*y` which is behind a `&` reference
-   |                  `y` is a `&` reference, so the data it refers to cannot be moved
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0507`.

src/test/ui/borrowck/borrowck-issue-2657-2.nll.stderr

@@ -8,17 +8,3 @@ LL |                 (|| { let bar = foo; bar.take() })();
            It represents potential unsoundness in your code.
            This warning will become a hard error in the future.
 
-warning[E0507]: cannot move out of `foo`, as it is immutable for the pattern guard
-  --> $DIR/borrowck-migrate-to-nll.rs:35:17
-   |
-LL |                 (|| { let bar = foo; bar.take() })();
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |                 |
-   |                 cannot move out of `foo`, as it is immutable for the pattern guard
-   |                 cannot move
-   |
-   = note: variables bound in patterns are immutable until the end of the pattern guard
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
-

src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr

@@ -8,17 +8,3 @@ LL |                 (|| { let bar = foo; bar.take() })();
            It represents potential unsoundness in your code.
            This warning will become a hard error in the future.
 
-warning[E0507]: cannot move out of `foo`, as it is immutable for the pattern guard
-  --> $DIR/borrowck-migrate-to-nll.rs:35:17
-   |
-LL |                 (|| { let bar = foo; bar.take() })();
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |                 |
-   |                 cannot move out of `foo`, as it is immutable for the pattern guard
-   |                 cannot move
-   |
-   = note: variables bound in patterns are immutable until the end of the pattern guard
-   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
-           It represents potential unsoundness in your code.
-           This warning will become a hard error in the future.
-