bjoernager/rust
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Point out correct turbofish usage on Foo<Bar<Baz>>

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Whenever we parse a chain of binary operations, as long as the first
operation is `<` and the subsequent operations are either `>` or `<`,
present the following diagnostic help:

    use `::<...>` instead of `<...>` if you meant to specify type arguments

This will lead to spurious recommendations on situations like
`2 < 3 < 4` but should be clear from context that the help doesn't apply
in that case.
This commit is contained in:
Esteban Küber 2017-03-13 19:07:47 -07:00
parent 6f10e2f63d
commit e3b8550a60
3 changed files with 61 additions and 1 deletions
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5
src/libsyntax/parse/parser.rs
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@ -2919,7 +2919,10 @@ impl<'a> Parser<'a> {
let op_span = mk_sp(op.span.lo, self.span.hi);
let mut err = self.diagnostic().struct_span_err(op_span,
"chained comparison operators require parentheses");
if op.node == BinOpKind::Lt && *outer_op == AssocOp::Greater {
if op.node == BinOpKind::Lt &&
*outer_op == AssocOp::Less || // Include `<` to provide this recommendation
*outer_op == AssocOp::Greater // even in a case like the following:
{ // Foo<Bar<Baz<Qux, ()>>>
err.help(
"use `::<...>` instead of `<...>` if you meant to specify type arguments");
}