bjoernager/rust
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Rollup merge of #86165 - m-ou-se:proc-macro-span-shrink, r=dtolnay

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Add proc_macro::Span::{before, after}.

This adds `proc_macro::Span::before()` and `proc_macro::Span::after()` to get a zero width span at the start or end of the span.

These are equivalent to rustc's `Span::shrink_to_lo()` and `Span::shrink_to_hi()` but with a less cryptic name. They are useful when generating diagnostlics like "missing \<thing\> after \<thing\>".

E.g.

```rust
syn::Error::new(ident.span().after(), "missing `:` after field name").into_compile_error()
```
This commit is contained in:
Manish Goregaokar 2021-09-10 08:23:14 -07:00 • committed by GitHub
commit 000dbd27f1
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6
compiler/rustc_expand/src/proc_macro_server.rs
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@ -758,6 +758,12 @@ impl server::Span for Rustc<'_> {
let loc = self.sess.source_map().lookup_char_pos(span.hi());
LineColumn { line: loc.line, column: loc.col.to_usize() }
}
fn before(&mut self, span: Self::Span) -> Self::Span {
span.shrink_to_lo()
}
fn after(&mut self, span: Self::Span) -> Self::Span {
span.shrink_to_hi()
}
fn join(&mut self, first: Self::Span, second: Self::Span) -> Option<Self::Span> {
let self_loc = self.sess.source_map().lookup_char_pos(first.lo());
let other_loc = self.sess.source_map().lookup_char_pos(second.lo());