| Issue |
126844
|
| Summary |
[clang-format] comment immediately preceding `} else` is incorrectly indented
|
| Labels |
clang-format
|
| Assignees |
|
| Reporter |
rjmccall
|
clang-format appears to believe that comments preceding `} else ...` lines should be indented as if they were part of the `if` block. In fact, this is often wrong.
Comments in this position *may* end a narrative about the behavior in the `if` block and say something useful about the control flow out of the block, e.g.
```
// Check for something bad.
if (someCondition) {
// Oh no, just blow everything up.
state.reset();
// Fall through and start over.
} else {
state.proceed();
}
```
In this case, it is appropriate for the comment to be indented at the level of the inner block.
However, it is more common that these comments continue a narrative about the control flow edge that didn't enter the `if` block:
```
// Check for something bad.
if (someCondition) {
// Oh no, just blow everything up.
state.reset();
// Fall through and start over.
// Thank goodness, we're fine.
} else {
state.proceed();
}
```
In this case, it is appropriate for the comment to be indented at the level of the outer block, i.e. the same level as the initial comment on the `if`.
This behavior of clang-format can be worked around by separating the end brace and the `else`, but of course this adds an extra line and misleadingly makes the `if` block look like it ends with no `else`:
```
// Check for something bad.
if (someCondition) {
// Oh no, just blow everything up.
state.reset();
// Fall through and start over.
}
// Thank goodness, we're fine.
else {
state.proceed();
}
```
As a special case, clang-format should check whether these comments match one or the other indentation and preserve that rather than assuming that naive re-indentation is appropriate.
We saw this misbehavior on several lines in the following LLVM PR: https://github.com/llvm/llvm-project/pull/126644
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