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Rollup merge of #85939 - m-ou-se:fix-remove-ref-macro-invocation, r=estebank

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Fix suggestion for removing &mut from &mut macro!().

Fixes #85933

Before: (Note the suggestions.)
```
error[E0308]: mismatched types
 --> src/main.rs:2:21
  |
2 |     let _: String = &mut format!("");
  |            ------   ^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `mut format!("")`
  |            expected due to this

error[E0308]: mismatched types
 --> src/main.rs:3:21
  |
3 |     let _: String = &mut (format!(""));
  |            ------   ^^^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `mut (format!(""))`
  |            expected due to this
```

After:
```
error[E0308]: mismatched types
 --> src/main.rs:2:21
  |
2 |     let _: String = &mut format!("");
  |            ------   ^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `format!("")`
  |            expected due to this

error[E0308]: mismatched types
 --> src/main.rs:3:21
  |
3 |     let _: String = &mut (format!(""));
  |            ------   ^^^^^^^^^^^^^^^^^^
  |            |        |
  |            |        expected struct `String`, found `&mut String`
  |            |        help: consider removing the borrow: `format!("")`
  |            expected due to this
```
This commit is contained in:
Yuki Okushi 2021-06-05 06:13:39 +09:00 committed by GitHub
commit 5ebc4d3697
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 36 additions and 4 deletions
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14
compiler/rustc_typeck/src/check/demand.rs
View File

@ -17,6 +17,7 @@
use super::method::probe;
use std::fmt;
use std::iter;
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
pub fn emit_coerce_suggestions(
@ -573,12 +574,19 @@ pub fn check_ref(
// We have `&T`, check if what was expected was `T`. If so,
// we may want to suggest removing a `&`.
if sm.is_imported(expr.span) {
if let Ok(src) = sm.span_to_snippet(sp) {
if let Some(src) = src.strip_prefix('&') {
// Go through the spans from which this span was expanded,
// and find the one that's pointing inside `sp`.
//
// E.g. for `&format!("")`, where we want the span to the
// `format!()` invocation instead of its expansion.
if let Some(call_span) =
iter::successors(Some(expr.span), |s| s.parent()).find(|&s| sp.contains(s))
{
if let Ok(code) = sm.span_to_snippet(call_span) {
return Some((
sp,
"consider removing the borrow",
src.to_string(),
code,
Applicability::MachineApplicable,
));
}

4
src/test/ui/suggestions/format-borrow.rs
View File

@ -3,4 +3,8 @@ fn main() {
//~^ ERROR mismatched types
let b: String = &format!("b");
//~^ ERROR mismatched types
let c: String = &mut format!("c");
//~^ ERROR mismatched types
let d: String = &mut (format!("d"));
//~^ ERROR mismatched types
}

22
src/test/ui/suggestions/format-borrow.stderr
View File

@ -18,6 +18,26 @@ LL | let b: String = &format!("b");
| | help: consider removing the borrow: `format!("b")`
| expected due to this
error: aborting due to 2 previous errors
error[E0308]: mismatched types
--> $DIR/format-borrow.rs:6:21
|
LL | let c: String = &mut format!("c");
| ------ ^^^^^^^^^^^^^^^^^
| | |
| | expected struct `String`, found `&mut String`
| | help: consider removing the borrow: `format!("c")`
| expected due to this
error[E0308]: mismatched types
--> $DIR/format-borrow.rs:8:21
|
LL | let d: String = &mut (format!("d"));
| ------ ^^^^^^^^^^^^^^^^^^^
| | |
| | expected struct `String`, found `&mut String`
| | help: consider removing the borrow: `format!("d")`
| expected due to this
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0308`.