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Improve error message when failing to parse a block

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We want to catch this error:

```
if (foo)
    bar;
```

as it's valid syntax in other languages, and say how to fix it.
Unfortunately it didn't care if the suggestion made sense and just
highlighted the unexpected token.

Now it attempts to parse a statement, and if it succeeds, it shows the
help message.

Fixes #35907
This commit is contained in:
James Miller 2016-08-23 18:23:31 +12:00
parent 3c5a0fa45b
commit 72d629caa5
2 changed files with 44 additions and 3 deletions
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27
src/libsyntax/parse/parser.rs
View file

@ -4087,9 +4087,30 @@ impl<'a> Parser<'a> {
if !self.eat(&token::OpenDelim(token::Brace)) {
let sp = self.span;
let tok = self.this_token_to_string();
return Err(self.span_fatal_help(sp,
&format!("expected `{{`, found `{}`", tok),
"place this code inside a block"));
let mut e = self.span_fatal(sp, &format!("expected `{{`, found `{}`", tok));
// Check to see if the user has written something like
//
// if (cond)
// bar;
//
// Which is valid in other languages, but not Rust.
match self.parse_stmt_without_recovery(false) {
Ok(Some(stmt)) => {
let mut stmt_span = stmt.span;
// expand the span to include the semicolon, if it exists
if self.eat(&token::Semi) {
stmt_span.hi = self.last_span.hi;
}
e.span_help(stmt_span, "try placing this code inside a block");
}
Err(mut e) => {
self.recover_stmt_(SemiColonMode::Break);
e.cancel();
}
_ => ()
}
return Err(e);
}
self.parse_block_tail(lo, BlockCheckMode::Default)