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#[repr(align="")] has terrible diagnostics #50314

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nagisa opened this issue Apr 29, 2018 · 0 comments
Closed

#[repr(align="")] has terrible diagnostics #50314

nagisa opened this issue Apr 29, 2018 · 0 comments
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A-diagnostics Area: Messages for errors, warnings, and lints

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@nagisa
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nagisa commented Apr 29, 2018

The attribute was fairly recently stabilised in form of #[repr(align(x))] however the RFC and some searches still refer to the attribute as #[repr(align="x")], in which case the compiler emits the following error:

error[E0552]: unrecognized representation hint
   --> libcore/../libcore/tests/slice.rs:574:12
    |
574 |     #[repr(align=8)] struct U64(u64, u64);
    |            ^^^^^^^

We should detect this case and inform users of the correct way to specify the alignment.

cc #33626
@nagisa nagisa added the A-diagnostics Area: Messages for errors, warnings, and lints label Apr 29, 2018
@varkor varkor mentioned this issue Apr 29, 2018
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bors added a commit that referenced this issue Apr 29, 2018
@bors
Auto merge of #50317 - varkor:repr-align-assign, r=nagisa
774a6a3 
Improve error message for #[repr(align=x)]

Before:
```
error[E0552]: unrecognized representation hint
 --> src/main.rs:1:8
  |
1 | #[repr(align="8")]
  |        ^^^^^^^^^
```
After:
```
error[E0693]: incorrect `repr(align)` attribute format
 --> src/main.rs:1:8
  |
2 | #[repr(align="8")]
  |        ^^^^^^^^^ help: use parentheses instead: `align(8)`
```

Fixes #50314.
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