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Rollup merge of #87953 - m-ou-se:closure-migration-multiline-formatting, r=petrochenkov

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Improve formatting of closure capture migration suggestion for multi-line closures.

Fixes https://github.com/rust-lang/rust/issues/87952

Before:
```
help: add a dummy let to cause `a` to be fully captured
  |
5 ~     let _ = || { let _ = &a;
6 +         dbg!(a.0);
7 ~     };
  |
```

After:
```
help: add a dummy let to cause `a` to be fully captured
  |
5 ~     let _ = || {
6 +         let _ = &a;
7 +         dbg!(a.0);
8 ~     };
  |
```
This commit is contained in:
Manish Goregaokar 2021-08-12 10:04:15 -07:00 • committed by GitHub
commit 0c4e37ad5c
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17 changed files with 119 additions and 83 deletions
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13
compiler/rustc_typeck/src/check/upvar.rs
View file

@ -649,11 +649,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
match self.tcx.sess.source_map().span_to_snippet(closure_body_span) {
Ok(s) => {
let trimmed = s.trim_start();
let mut lines = trimmed.lines();
let line1 = lines.next().unwrap_or_default();
// If the closure contains a block then replace the opening brace
// with "{ let _ = (..); "
let sugg = if let Some('{') = trimmed.chars().next() {
format!("{{ {}; {}", migration_string, &trimmed[1..])
let sugg = if line1.trim_end() == "{" {
// This is a multi-line closure with just a `{` on the first line,
// so we put the `let` on its own line.
// We take the indentation from the next non-empty line.
let line2 = lines.filter(|line| !line.is_empty()).next().unwrap_or_default();
let indent = line2.split_once(|c: char| !c.is_whitespace()).unwrap_or_default().0;
format!("{{\n{}{};{}", indent, migration_string, &trimmed[line1.len()..])
} else if line1.starts_with('{') {
format!("{{ {}; {}", migration_string, &trimmed[1..].trim_start())
} else {
format!("{{ {}; {} }}", migration_string, s)
};