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Auto merge of #43096 - estebank:ascription-help, r=nikomatsakis

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Point at `:` when using it instead of `;`

When triggering type ascription in such a way that we can infer a
statement end was intended, add a suggestion for the change. Always
point out the reason for the expectation of a type is due to type
ascription.

Fix #42057, #41928.
This commit is contained in:
bors 2017-07-23 20:56:20 +00:00
commit afe145d227
11 changed files with 174 additions and 18 deletions
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17
src/libsyntax/parse/parser.rs
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@ -2798,7 +2798,22 @@ impl<'a> Parser<'a> {
lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
continue
} else if op == AssocOp::Colon {
lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
Ok(lhs) => lhs,
Err(mut err) => {
err.span_label(self.span,
"expecting a type here because of type ascription");
let cm = self.sess.codemap();
let cur_pos = cm.lookup_char_pos(self.span.lo);
let op_pos = cm.lookup_char_pos(cur_op_span.hi);
if cur_pos.line != op_pos.line {
err.span_suggestion_short(cur_op_span,
"did you mean to use `;` here?",
";".to_string());
}
return Err(err);
}
};
continue
} else if op == AssocOp::DotDot || op == AssocOp::DotDotDot {
// If we didn’t have to handle `x..`/`x...`, it would be pretty easy to