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Auto merge of #76171 - estebank:turbofish-the-revenge, r=davidtwco

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Detect turbofish with multiple type params missing leading `::`

Fix #76072.
This commit is contained in:
bors 2020-09-15 10:14:52 +00:00
commit 90b1f5ae59
4 changed files with 167 additions and 9 deletions
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46
compiler/rustc_parse/src/parser/diagnostics.rs
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@ -553,6 +553,52 @@ impl<'a> Parser<'a> {
}
}
/// When writing a turbofish with multiple type parameters missing the leading `::`, we will
/// encounter a parse error when encountering the first `,`.
pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
&mut self,
mut e: DiagnosticBuilder<'a>,
expr: &mut P<Expr>,
) -> PResult<'a, ()> {
if let ExprKind::Binary(binop, _, _) = &expr.kind {
if let ast::BinOpKind::Lt = binop.node {
if self.eat(&token::Comma) {
let x = self.parse_seq_to_before_end(
&token::Gt,
SeqSep::trailing_allowed(token::Comma),
|p| p.parse_ty(),
);
match x {
Ok((_, _, false)) => {
self.bump(); // `>`
match self.parse_expr() {
Ok(_) => {
e.span_suggestion_verbose(
binop.span.shrink_to_lo(),
"use `::<...>` instead of `<...>` to specify type arguments",
"::".to_string(),
Applicability::MaybeIncorrect,
);
e.emit();
*expr = self.mk_expr_err(expr.span.to(self.prev_token.span));
return Ok(());
}
Err(mut err) => {
err.cancel();
}
}
}
Err(mut err) => {
err.cancel();
}
_ => {}
}
}
}
}
Err(e)
}
/// Check to see if a pair of chained operators looks like an attempt at chained comparison,
/// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
/// parenthesising the leftmost comparison.