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Auto merge of #85427 - ehuss:fix-use-placement, r=jackh726

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Fix use placement for suggestions near main.

This fixes an edge case for the suggestion to add a `use`. When running with `--test`, the `main` function will be annotated with an `#[allow(dead_code)]` attribute. The `UsePlacementFinder` would end up using the dummy span of that synthetic attribute. If there are top-level inner attributes, this would place the `use` in the wrong position. The solution here is to ignore attributes with dummy spans.

In the process of working on this, I discovered that the `use_suggestion_placement` test was broken. `UsePlacementFinder` is unaware of active attributes. Attributes like `#[derive]` don't exist in the AST since they are removed. Fixing that is difficult, since the AST does not retain enough information. I considered trying to place the `use` towards the top of the module after any `extern crate` items, but I couldn't find a way to get a span for the start of a module block (the `mod` span starts at the `mod` keyword, and it seems tricky to find the spot just after the opening bracket and past inner attributes). For now, I just put some comments about the issue. This appears to have been a known issue in #44215 where the test for it was introduced, and the fix seemed to be deferred to later.
This commit is contained in:
bors 2021-06-24 14:56:28 +00:00
commit d95745e5fa
11 changed files with 167 additions and 20 deletions
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16
compiler/rustc_resolve/src/lib.rs
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@ -335,15 +335,15 @@ impl UsePlacementFinder {
if self.span.map_or(true, |span| item.span < span)
&& !item.span.from_expansion()
{
self.span = Some(item.span.shrink_to_lo());
// don't insert between attributes and an item
if item.attrs.is_empty() {
self.span = Some(item.span.shrink_to_lo());
} else {
// find the first attribute on the item
for attr in &item.attrs {
if self.span.map_or(true, |span| attr.span < span) {
self.span = Some(attr.span.shrink_to_lo());
}
// find the first attribute on the item
// FIXME: This is broken for active attributes.
for attr in &item.attrs {
if !attr.span.is_dummy()
&& self.span.map_or(true, |span| attr.span < span)
{
self.span = Some(attr.span.shrink_to_lo());
}
}
}