Fix move errors for index expressions

The suggestion logic gave up too early, which kept it from suggesting
borrowing index expressions.

diff --git a/src/librustc_mir/borrow_check/move_errors.rs b/src/librustc_mir/borrow_check/move_errors.rs
index c641e960ac5aaf24826034c58b9c973f8bb42da3..961d8eb7b948b2264d66f3ec970838a50d2e9158 100644 (file)
--- a/src/librustc_mir/borrow_check/move_errors.rs
+++ b/src/librustc_mir/borrow_check/move_errors.rs
@@ -341,38 +341,32 @@ fn add_move_hints(
                 move_from,
                 ..
             } => {
-                let mut suggest_change_head_expr = false;
-                match move_from {
+                let try_remove_deref = match move_from {
                     Place::Projection(box PlaceProjection {
                         elem: ProjectionElem::Deref,
                         ..
-                    }) => {
-                        // This is false for (e.g.) index expressions `a[b]`,
-                        // which roughly desugar to `*Index::index(&a, b)` or
-                        // `*IndexMut::index_mut(&mut a, b)`.
-                        if snippet.starts_with('*') {
-                            err.span_suggestion(
-                                span,
-                                "consider removing this dereference operator",
-                                (&snippet[1..]).to_owned(),
-                            );
-                            suggest_change_head_expr = true;
-                        }
-                    }
-                    _ => {
-                        err.span_suggestion(
-                            span,
-                            "consider using a reference instead",
-                            format!("&{}", snippet),
-                        );
-                        suggest_change_head_expr = true;
-                    }
+                    }) => true,
+                    _ => false,
+                };
+                if try_remove_deref && snippet.starts_with('*') {
+                    // This is false for (e.g.) index expressions `a[b]`,
+                    // which roughly desugar to `*Index::index(&a, b)` or
+                    // `*IndexMut::index_mut(&mut a, b)`.
+                    err.span_suggestion(
+                        span,
+                        "consider removing this dereference operator",
+                        snippet[1..].to_owned(),
+                    );
+                } else {
+                    err.span_suggestion(
+                        span,
+                        "consider using a reference instead",
+                        format!("&{}", snippet),
+                    );
                 }
+
                 binds_to.sort();
                 binds_to.dedup();
-                if !suggest_change_head_expr {
-                    self.add_move_error_suggestions(err, &binds_to);
-                }
                 self.add_move_error_labels(err, &binds_to);
             }
             GroupedMoveError::MovesFromValue { mut binds_to, .. } => {

diff --git a/src/test/ui/suggestions/dont-suggest-ref.stderr b/src/test/ui/suggestions/dont-suggest-ref.stderr
index d27c028fe47d3d0c1e0e0e64791390fd490ec507..16f11f9b10ab249010197af8adc16fc07fc33e21 100644 (file)
--- a/src/test/ui/suggestions/dont-suggest-ref.stderr
+++ b/src/test/ui/suggestions/dont-suggest-ref.stderr
@@ -188,8 +188,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:111:17
    |
 LL |     let X(_t) = vs_[0];
-   |           --    ^^^^^^ cannot move out of borrowed content
-   |           |
+   |           --    ^^^^^^
+   |           |     |
+   |           |     cannot move out of borrowed content
+   |           |     help: consider using a reference instead: `&vs_[0]`
    |           data moved here
    |
 note: move occurs because _t has type `Y`, which does not implement the `Copy` trait
@@ -202,8 +204,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:115:30
    |
 LL |     if let Either::One(_t) = vr[0] { }
-   |                        --    ^^^^^ cannot move out of borrowed content
-   |                        |
+   |                        --    ^^^^^
+   |                        |     |
+   |                        |     cannot move out of borrowed content
+   |                        |     help: consider using a reference instead: `&vr[0]`
    |                        data moved here
    |
 note: move occurs because _t has type `X`, which does not implement the `Copy` trait
@@ -216,8 +220,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:119:33
    |
 LL |     while let Either::One(_t) = vr[0] { }
-   |                           --    ^^^^^ cannot move out of borrowed content
-   |                           |
+   |                           --    ^^^^^
+   |                           |     |
+   |                           |     cannot move out of borrowed content
+   |                           |     help: consider using a reference instead: `&vr[0]`
    |                           data moved here
    |
 note: move occurs because _t has type `X`, which does not implement the `Copy` trait
@@ -230,7 +236,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:123:11
    |
 LL |     match vr[0] {
-   |           ^^^^^ cannot move out of borrowed content
+   |           ^^^^^
+   |           |
+   |           cannot move out of borrowed content
+   |           help: consider using a reference instead: `&vr[0]`
 ...
 LL |         Either::One(_t)
    |                     -- data moved here
@@ -245,7 +254,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:130:11
    |
 LL |     match vr[0] {
-   |           ^^^^^ cannot move out of borrowed content
+   |           ^^^^^
+   |           |
+   |           cannot move out of borrowed content
+   |           help: consider using a reference instead: `&vr[0]`
 ...
 LL |         Either::One(_t) => (),
    |                     -- data moved here
@@ -260,8 +272,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:139:17
    |
 LL |     let X(_t) = vsm[0];
-   |           --    ^^^^^^ cannot move out of borrowed content
-   |           |
+   |           --    ^^^^^^
+   |           |     |
+   |           |     cannot move out of borrowed content
+   |           |     help: consider using a reference instead: `&vsm[0]`
    |           data moved here
    |
 note: move occurs because _t has type `Y`, which does not implement the `Copy` trait
@@ -274,8 +288,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:143:30
    |
 LL |     if let Either::One(_t) = vrm[0] { }
-   |                        --    ^^^^^^ cannot move out of borrowed content
-   |                        |
+   |                        --    ^^^^^^
+   |                        |     |
+   |                        |     cannot move out of borrowed content
+   |                        |     help: consider using a reference instead: `&vrm[0]`
    |                        data moved here
    |
 note: move occurs because _t has type `X`, which does not implement the `Copy` trait
@@ -288,8 +304,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:147:33
    |
 LL |     while let Either::One(_t) = vrm[0] { }
-   |                           --    ^^^^^^ cannot move out of borrowed content
-   |                           |
+   |                           --    ^^^^^^
+   |                           |     |
+   |                           |     cannot move out of borrowed content
+   |                           |     help: consider using a reference instead: `&vrm[0]`
    |                           data moved here
    |
 note: move occurs because _t has type `X`, which does not implement the `Copy` trait
@@ -302,7 +320,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:151:11
    |
 LL |     match vrm[0] {
-   |           ^^^^^^ cannot move out of borrowed content
+   |           ^^^^^^
+   |           |
+   |           cannot move out of borrowed content
+   |           help: consider using a reference instead: `&vrm[0]`
 ...
 LL |         Either::One(_t)
    |                     -- data moved here
@@ -317,7 +338,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:158:11
    |
 LL |     match vrm[0] {
-   |           ^^^^^^ cannot move out of borrowed content
+   |           ^^^^^^
+   |           |
+   |           cannot move out of borrowed content
+   |           help: consider using a reference instead: `&vrm[0]`
 ...
 LL |         Either::One(_t) => (),
    |                     -- data moved here
@@ -332,7 +356,10 @@ error[E0507]: cannot move out of borrowed content
   --> $DIR/dont-suggest-ref.rs:166:11
    |
 LL |     match vrm[0] {
-   |           ^^^^^^ cannot move out of borrowed content
+   |           ^^^^^^
+   |           |
+   |           cannot move out of borrowed content
+   |           help: consider using a reference instead: `&vrm[0]`
 ...
 LL |         Either::One(_t) => (),
    |                     -- data moved here