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jruderman opened this issue Sep 10, 2021 · 0 comments · Fixed by #88894
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Diagnostic for impl for S should also suggest syntax for inherit impl #88818

jruderman opened this issue Sep 10, 2021 · 0 comments · Fixed by #88894
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A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@jruderman
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jruderman commented Sep 10, 2021 •
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Given the following code: 

struct S { }
impl for S { }

The current output is:

error: missing trait in a trait impl
 --> src/lib.rs:2:5
  |
2 | impl for S { }
  |     ^

Ideally the output should look like:

help: to implement trait items for struct S, write `impl TraitName for S { ... }`
help: to implement inherit items for struct S, write `impl S { ... }`

Followup to #56031
@jruderman jruderman added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 10, 2021
@FabianWolff FabianWolff mentioned this issue Sep 12, 2021
Merged
workingjubilee added a commit to workingjubilee/rustc that referenced this issue Sep 14, 2021
@workingjubilee
Rollup merge of rust-lang#88894 - FabianWolff:issue-88818, r=estebank
b190806 
Improve error message for missing trait in trait impl

Fixes rust-lang#88818. For the following example:
```rust
struct S { }
impl for S { }
```
the current output is:
```
error: missing trait in a trait impl
 --> t1.rs:2:5
  |
2 | impl for S { }
  |     ^
```
With my changes, I get:
```
error: missing trait in a trait impl
 --> t1.rs:2:5
  |
2 | impl for S { }
  |     ^
  |
help: add a trait here
  |
2 | impl Trait for S { }
  |      +++++
help: for an inherent impl, drop this `for`
  |
2 - impl for S { }
2 + impl S { }
  |
```
workingjubilee added a commit to workingjubilee/rustc that referenced this issue Sep 14, 2021
@workingjubilee
Rollup merge of rust-lang#88894 - FabianWolff:issue-88818, r=estebank
337ca88 
Improve error message for missing trait in trait impl

Fixes rust-lang#88818. For the following example:
```rust
struct S { }
impl for S { }
```
the current output is:
```
error: missing trait in a trait impl
 --> t1.rs:2:5
  |
2 | impl for S { }
  |     ^
```
With my changes, I get:
```
error: missing trait in a trait impl
 --> t1.rs:2:5
  |
2 | impl for S { }
  |     ^
  |
help: add a trait here
  |
2 | impl Trait for S { }
  |      +++++
help: for an inherent impl, drop this `for`
  |
2 - impl for S { }
2 + impl S { }
  |
```
@bors bors closed this as completed in 84d65fe Sep 14, 2021
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Improve error message for missing trait in trait impl FabianWolff/rust
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