Account for dereference expressions

estebank · estebank · commit cf0b6b933735 · 2022-12-13T10:06:15.000-08:00
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -410,13 +410,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     fn add_move_hints(&self, error: GroupedMoveError<'tcx>, err: &mut Diagnostic, span: Span) {
         match error {
             GroupedMoveError::MovesFromPlace { mut binds_to, move_from, .. } => {
-                err.span_suggestion_verbose(
-                    span.shrink_to_lo(),
-                    "consider borrowing here",
-                    "&".to_string(),
-                    Applicability::Unspecified,
-                );
-
+                self.add_borrow_suggestions(err, span);
                 if binds_to.is_empty() {
                     let place_ty = move_from.ty(self.body, self.infcx.tcx).ty;
                     let place_desc = match self.describe_place(move_from.as_ref()) {
@@ -459,6 +453,27 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         }
     }
 
+    fn add_borrow_suggestions(&self, err: &mut Diagnostic, span: Span) {
+        match self.infcx.tcx.sess.source_map().span_to_snippet(span) {
+            Ok(snippet) if snippet.starts_with('*') => {
+                err.span_suggestion_verbose(
+                    span.with_hi(span.lo() + BytePos(1)),
+                    "consider removing the dereference here",
+                    String::new(),
+                    Applicability::MaybeIncorrect,
+                );
+            }
+            _ => {
+                err.span_suggestion_verbose(
+                    span.shrink_to_lo(),
+                    "consider borrowing here",
+                    "&".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+            }
+        }
+    }
+
     fn add_move_error_suggestions(&self, err: &mut Diagnostic, binds_to: &[Local]) {
         let mut suggestions: Vec<(Span, String, String)> = Vec::new();
         for local in binds_to {
diff --git a/src/test/ui/borrowck/access-mode-in-closures.stderr b/src/test/ui/borrowck/access-mode-in-closures.stderr
@@ -7,10 +7,11 @@ LL |         match *s { S(v) => v }
    |                      data moved here
    |                      move occurs because `v` has type `Vec<isize>`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -         match *s { S(v) => v }
+LL +         match s { S(v) => v }
    |
-LL |         match &*s { S(v) => v }
-   |               +
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-issue-2657-2.fixed b/src/test/ui/borrowck/borrowck-issue-2657-2.fixed
@@ -0,0 +1,12 @@
+// run-rustfix
+fn main() {
+
+    let x: Option<Box<_>> = Some(Box::new(1));
+
+    match x {
+      Some(ref y) => {
+        let _b = y; //~ ERROR cannot move out
+      }
+      _ => {}
+    }
+}
diff --git a/src/test/ui/borrowck/borrowck-issue-2657-2.rs b/src/test/ui/borrowck/borrowck-issue-2657-2.rs
@@ -1,3 +1,4 @@
+// run-rustfix
 fn main() {
 
     let x: Option<Box<_>> = Some(Box::new(1));
diff --git a/src/test/ui/borrowck/borrowck-issue-2657-2.stderr b/src/test/ui/borrowck/borrowck-issue-2657-2.stderr
@@ -1,13 +1,14 @@
 error[E0507]: cannot move out of `*y` which is behind a shared reference
-  --> $DIR/borrowck-issue-2657-2.rs:7:18
+  --> $DIR/borrowck-issue-2657-2.rs:8:18
    |
 LL |         let _b = *y;
    |                  ^^ move occurs because `*y` has type `Box<i32>`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -         let _b = *y;
+LL +         let _b = y;
    |
-LL |         let _b = &*y;
-   |                  +
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-move-error-with-note.fixed b/src/test/ui/borrowck/borrowck-move-error-with-note.fixed
@@ -10,7 +10,7 @@ enum Foo {
 
 fn blah() {
     let f = &Foo::Foo1(Box::new(1), Box::new(2));
-    match &*f { //~ ERROR cannot move out of
+    match f { //~ ERROR cannot move out of
         Foo::Foo1(num1,
                   num2) => (),
         Foo::Foo2(num) => (),
diff --git a/src/test/ui/borrowck/borrowck-move-error-with-note.stderr b/src/test/ui/borrowck/borrowck-move-error-with-note.stderr
@@ -11,10 +11,11 @@ LL |         Foo::Foo2(num) => (),
    |                   --- ...and here
    |
    = note: move occurs because these variables have types that don't implement the `Copy` trait
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     match *f {
+LL +     match f {
    |
-LL |     match &*f {
-   |           +
 
 error[E0509]: cannot move out of type `S`, which implements the `Drop` trait
   --> $DIR/borrowck-move-error-with-note.rs:30:11
diff --git a/src/test/ui/borrowck/borrowck-move-from-unsafe-ptr.stderr b/src/test/ui/borrowck/borrowck-move-from-unsafe-ptr.stderr
@@ -4,10 +4,11 @@ error[E0507]: cannot move out of `*x` which is behind a raw pointer
 LL |     let y = *x;
    |             ^^ move occurs because `*x` has type `Box<isize>`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let y = *x;
+LL +     let y = x;
    |
-LL |     let y = &*x;
-   |             +
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/borrowck-move-out-of-overloaded-deref.stderr b/src/test/ui/borrowck/borrowck-move-out-of-overloaded-deref.stderr
@@ -4,10 +4,11 @@ error[E0507]: cannot move out of an `Rc`
 LL |     let _x = *Rc::new("hi".to_string());
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let _x = *Rc::new("hi".to_string());
+LL +     let _x = Rc::new("hi".to_string());
    |
-LL |     let _x = &*Rc::new("hi".to_string());
-   |              +
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/borrowck/issue-20801.stderr b/src/test/ui/borrowck/issue-20801.stderr
@@ -4,43 +4,47 @@ error[E0507]: cannot move out of a mutable reference
 LL |     let a = unsafe { *mut_ref() };
    |                      ^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let a = unsafe { *mut_ref() };
+LL +     let a = unsafe { mut_ref() };
    |
-LL |     let a = unsafe { &*mut_ref() };
-   |                      +
 
 error[E0507]: cannot move out of a shared reference
   --> $DIR/issue-20801.rs:29:22
    |
 LL |     let b = unsafe { *imm_ref() };
    |                      ^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let b = unsafe { *imm_ref() };
+LL +     let b = unsafe { imm_ref() };
    |
-LL |     let b = unsafe { &*imm_ref() };
-   |                      +
 
 error[E0507]: cannot move out of a raw pointer
   --> $DIR/issue-20801.rs:32:22
    |
 LL |     let c = unsafe { *mut_ptr() };
    |                      ^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let c = unsafe { *mut_ptr() };
+LL +     let c = unsafe { mut_ptr() };
    |
-LL |     let c = unsafe { &*mut_ptr() };
-   |                      +
 
 error[E0507]: cannot move out of a raw pointer
   --> $DIR/issue-20801.rs:35:22
    |
 LL |     let d = unsafe { *const_ptr() };
    |                      ^^^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let d = unsafe { *const_ptr() };
+LL +     let d = unsafe { const_ptr() };
    |
-LL |     let d = unsafe { &*const_ptr() };
-   |                      +
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/borrowck/issue-54597-reject-move-out-of-borrow-via-pat.stderr b/src/test/ui/borrowck/issue-54597-reject-move-out-of-borrow-via-pat.stderr
@@ -4,10 +4,11 @@ error[E0507]: cannot move out of `*array` which is behind a shared reference
 LL |             *array
    |             ^^^^^^ move occurs because `*array` has type `Vec<Value>`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -             *array
+LL +             array
    |
-LL |             &*array
-   |             +
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/moves/move-out-of-array-ref.stderr b/src/test/ui/moves/move-out-of-array-ref.stderr
@@ -7,10 +7,11 @@ LL |     let [_, e, _, _] = *a;
    |             data moved here
    |             move occurs because `e` has type `D`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let [_, e, _, _] = *a;
+LL +     let [_, e, _, _] = a;
    |
-LL |     let [_, e, _, _] = &*a;
-   |                        +
 
 error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
   --> $DIR/move-out-of-array-ref.rs:13:27
@@ -21,10 +22,11 @@ LL |     let [_, s @ .. , _] = *a;
    |             data moved here
    |             move occurs because `s` has type `[D; 2]`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let [_, s @ .. , _] = *a;
+LL +     let [_, s @ .. , _] = a;
    |
-LL |     let [_, s @ .. , _] = &*a;
-   |                           +
 
 error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
   --> $DIR/move-out-of-array-ref.rs:18:24
@@ -35,10 +37,11 @@ LL |     let [_, e, _, _] = *a;
    |             data moved here
    |             move occurs because `e` has type `D`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let [_, e, _, _] = *a;
+LL +     let [_, e, _, _] = a;
    |
-LL |     let [_, e, _, _] = &*a;
-   |                        +
 
 error[E0508]: cannot move out of type `[D; 4]`, a non-copy array
   --> $DIR/move-out-of-array-ref.rs:23:27
@@ -49,10 +52,11 @@ LL |     let [_, s @ .. , _] = *a;
    |             data moved here
    |             move occurs because `s` has type `[D; 2]`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let [_, s @ .. , _] = *a;
+LL +     let [_, s @ .. , _] = a;
    |
-LL |     let [_, s @ .. , _] = &*a;
-   |                           +
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/nll/cannot-move-block-spans.stderr b/src/test/ui/nll/cannot-move-block-spans.stderr
@@ -4,32 +4,35 @@ error[E0507]: cannot move out of `*r` which is behind a shared reference
 LL |     let x = { *r };
    |               ^^ move occurs because `*r` has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let x = { *r };
+LL +     let x = { r };
    |
-LL |     let x = { &*r };
-   |               +
 
 error[E0507]: cannot move out of `*r` which is behind a shared reference
   --> $DIR/cannot-move-block-spans.rs:6:22
    |
 LL |     let y = unsafe { *r };
    |                      ^^ move occurs because `*r` has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let y = unsafe { *r };
+LL +     let y = unsafe { r };
    |
-LL |     let y = unsafe { &*r };
-   |                      +
 
 error[E0507]: cannot move out of `*r` which is behind a shared reference
   --> $DIR/cannot-move-block-spans.rs:7:26
    |
 LL |     let z = loop { break *r; };
    |                          ^^ move occurs because `*r` has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let z = loop { break *r; };
+LL +     let z = loop { break r; };
    |
-LL |     let z = loop { break &*r; };
-   |                          +
 
 error[E0508]: cannot move out of type `[String; 2]`, a non-copy array
   --> $DIR/cannot-move-block-spans.rs:11:15
@@ -79,32 +82,35 @@ error[E0507]: cannot move out of `*r` which is behind a shared reference
 LL |     let x = { let mut u = 0; u += 1; *r };
    |                                      ^^ move occurs because `*r` has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let x = { let mut u = 0; u += 1; *r };
+LL +     let x = { let mut u = 0; u += 1; r };
    |
-LL |     let x = { let mut u = 0; u += 1; &*r };
-   |                                      +
 
 error[E0507]: cannot move out of `*r` which is behind a shared reference
   --> $DIR/cannot-move-block-spans.rs:18:45
    |
 LL |     let y = unsafe { let mut u = 0; u += 1; *r };
    |                                             ^^ move occurs because `*r` has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let y = unsafe { let mut u = 0; u += 1; *r };
+LL +     let y = unsafe { let mut u = 0; u += 1; r };
    |
-LL |     let y = unsafe { let mut u = 0; u += 1; &*r };
-   |                                             +
 
 error[E0507]: cannot move out of `*r` which is behind a shared reference
   --> $DIR/cannot-move-block-spans.rs:19:49
    |
 LL |     let z = loop { let mut u = 0; u += 1; break *r; u += 2; };
    |                                                 ^^ move occurs because `*r` has type `String`, which does not implement the `Copy` trait
    |
-help: consider borrowing here
+help: consider removing the dereference here
+   |
+LL -     let z = loop { let mut u = 0; u += 1; break *r; u += 2; };
+LL +     let z = loop { let mut u = 0; u += 1; break r; u += 2; };
    |
-LL |     let z = loop { let mut u = 0; u += 1; break &*r; u += 2; };
-   |                                                 +
 
 error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/nll/move-errors.stderr b/src/test/ui/nll/move-errors.stderr
diff --git a/src/test/ui/std-uncopyable-atomics.stderr b/src/test/ui/std-uncopyable-atomics.stderr
diff --git a/src/test/ui/suggestions/dont-suggest-ref/simple.rs b/src/test/ui/suggestions/dont-suggest-ref/simple.rs
diff --git a/src/test/ui/suggestions/dont-suggest-ref/simple.stderr b/src/test/ui/suggestions/dont-suggest-ref/simple.stderr

Original file line number	Diff line number	Diff line change
`@@ -7,10 +7,11 @@ LL \| match *s { S(v) => v }`
`7`	`7`	`\| data moved here`
`8`	`8`	\| move occurs because `v` has type `Vec<isize>`, which does not implement the `Copy` trait
`9`	`9`	`\|`
`10`		`-help: consider borrowing here`
	`10`	`+help: consider removing the dereference here`
	`11`	`+ \|`
	`12`	`+LL - match *s { S(v) => v }`
	`13`	`+LL + match s { S(v) => v }`
`11`	`14`	`\|`
`12`		`-LL \| match &*s { S(v) => v }`
`13`		`- \| +`
`14`	`15`
`15`	`16`	`error: aborting due to previous error`
`16`	`17`
Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,4 @@`
	`1`	`+// run-rustfix`
`1`	`2`	`fn main() {`
`2`	`3`
`3`	`4`	`let x: Option<Box<_>> = Some(Box::new(1));`
Original file line number	Diff line number	Diff line change
`@@ -1,13 +1,14 @@`
`1`	`1`	error[E0507]: cannot move out of `*y` which is behind a shared reference
`2`		`- --> $DIR/borrowck-issue-2657-2.rs:7:18`
	`2`	`+ --> $DIR/borrowck-issue-2657-2.rs:8:18`
`3`	`3`	`\|`
`4`	`4`	`LL \| let _b = *y;`
`5`	`5`	\| ^^ move occurs because `*y` has type `Box<i32>`, which does not implement the `Copy` trait
`6`	`6`	`\|`
`7`		`-help: consider borrowing here`
	`7`	`+help: consider removing the dereference here`
	`8`	`+ \|`
	`9`	`+LL - let _b = *y;`
	`10`	`+LL + let _b = y;`
`8`	`11`	`\|`
`9`		`-LL \| let _b = &*y;`
`10`		`- \| +`
`11`	`12`
`12`	`13`	`error: aborting due to previous error`
`13`	`14`
Original file line number	Diff line number	Diff line change
`@@ -11,10 +11,11 @@ LL \| Foo::Foo2(num) => (),`
`11`	`11`	`\| --- ...and here`
`12`	`12`	`\|`
`13`	`13`	= note: move occurs because these variables have types that don't implement the `Copy` trait
`14`		`-help: consider borrowing here`
	`14`	`+help: consider removing the dereference here`
	`15`	`+ \|`
	`16`	`+LL - match *f {`
	`17`	`+LL + match f {`
`15`	`18`	`\|`
`16`		`-LL \| match &*f {`
`17`		`- \| +`
`18`	`19`
`19`	`20`	error[E0509]: cannot move out of type `S`, which implements the `Drop` trait
`20`	`21`	`--> $DIR/borrowck-move-error-with-note.rs:30:11`
Original file line number	Diff line number	Diff line change
@@ -4,10 +4,11 @@ error[E0507]: cannot move out of `*x` which is behind a raw pointer
`4`	`4`	`LL \| let y = *x;`
`5`	`5`	\| ^^ move occurs because `*x` has type `Box<isize>`, which does not implement the `Copy` trait
`6`	`6`	`\|`
`7`		`-help: consider borrowing here`
	`7`	`+help: consider removing the dereference here`
	`8`	`+ \|`
	`9`	`+LL - let y = *x;`
	`10`	`+LL + let y = x;`
`8`	`11`	`\|`
`9`		`-LL \| let y = &*x;`
`10`		`- \| +`
`11`	`12`
`12`	`13`	`error: aborting due to previous error`
`13`	`14`
Original file line number	Diff line number	Diff line change
@@ -4,10 +4,11 @@ error[E0507]: cannot move out of an `Rc`
`4`	`4`	`LL \| let _x = *Rc::new("hi".to_string());`
`5`	`5`	\| ^^^^^^^^^^^^^^^^^^^^^^^^^^ move occurs because value has type `String`, which does not implement the `Copy` trait
`6`	`6`	`\|`
`7`		`-help: consider borrowing here`
	`7`	`+help: consider removing the dereference here`
	`8`	`+ \|`
	`9`	`+LL - let _x = *Rc::new("hi".to_string());`
	`10`	`+LL + let _x = Rc::new("hi".to_string());`
`8`	`11`	`\|`
`9`		`-LL \| let _x = &*Rc::new("hi".to_string());`
`10`		`- \| +`
`11`	`12`
`12`	`13`	`error: aborting due to previous error`
`13`	`14`
Original file line number	Diff line number	Diff line change
`@@ -4,43 +4,47 @@ error[E0507]: cannot move out of a mutable reference`
`4`	`4`	`LL \| let a = unsafe { *mut_ref() };`
`5`	`5`	\| ^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
`6`	`6`	`\|`
`7`		`-help: consider borrowing here`
	`7`	`+help: consider removing the dereference here`
	`8`	`+ \|`
	`9`	`+LL - let a = unsafe { *mut_ref() };`
	`10`	`+LL + let a = unsafe { mut_ref() };`
`8`	`11`	`\|`
`9`		`-LL \| let a = unsafe { &*mut_ref() };`
`10`		`- \| +`
`11`	`12`
`12`	`13`	`error[E0507]: cannot move out of a shared reference`
`13`	`14`	`--> $DIR/issue-20801.rs:29:22`
`14`	`15`	`\|`
`15`	`16`	`LL \| let b = unsafe { *imm_ref() };`
`16`	`17`	\| ^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
`17`	`18`	`\|`
`18`		`-help: consider borrowing here`
	`19`	`+help: consider removing the dereference here`
	`20`	`+ \|`
	`21`	`+LL - let b = unsafe { *imm_ref() };`
	`22`	`+LL + let b = unsafe { imm_ref() };`
`19`	`23`	`\|`
`20`		`-LL \| let b = unsafe { &*imm_ref() };`
`21`		`- \| +`
`22`	`24`
`23`	`25`	`error[E0507]: cannot move out of a raw pointer`
`24`	`26`	`--> $DIR/issue-20801.rs:32:22`
`25`	`27`	`\|`
`26`	`28`	`LL \| let c = unsafe { *mut_ptr() };`
`27`	`29`	\| ^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
`28`	`30`	`\|`
`29`		`-help: consider borrowing here`
	`31`	`+help: consider removing the dereference here`
	`32`	`+ \|`
	`33`	`+LL - let c = unsafe { *mut_ptr() };`
	`34`	`+LL + let c = unsafe { mut_ptr() };`
`30`	`35`	`\|`
`31`		`-LL \| let c = unsafe { &*mut_ptr() };`
`32`		`- \| +`
`33`	`36`
`34`	`37`	`error[E0507]: cannot move out of a raw pointer`
`35`	`38`	`--> $DIR/issue-20801.rs:35:22`
`36`	`39`	`\|`
`37`	`40`	`LL \| let d = unsafe { *const_ptr() };`
`38`	`41`	\| ^^^^^^^^^^^^ move occurs because value has type `T`, which does not implement the `Copy` trait
`39`	`42`	`\|`
`40`		`-help: consider borrowing here`
	`43`	`+help: consider removing the dereference here`
	`44`	`+ \|`
	`45`	`+LL - let d = unsafe { *const_ptr() };`
	`46`	`+LL + let d = unsafe { const_ptr() };`
`41`	`47`	`\|`
`42`		`-LL \| let d = unsafe { &*const_ptr() };`
`43`		`- \| +`
`44`	`48`
`45`	`49`	`error: aborting due to 4 previous errors`
`46`	`50`