Continue parsing after parent type args and suggest using angle brackets

[estebank]

error[E0214]: parenthesized parameters may only be used with a trait
--> $DIR/E0214.rs:2:15
|
LL | let v: Vec(&str) = vec!["foo"];
| ^^^^^^
| |
| only traits may use parentheses
| help: use angle brackets instead: `<&str>`

r? @zackmdavis

[zackmdavis]

No time to dig into it now, but I'm mildly curious about the history of this rule. Offhand, I don't seem to recall seeing traits use parentheses for type argum—oh, never mind, I just read --explain 214, and it points out that it's for Fn(T) types.

This does seem sufficiently remote from the crux of the error at hand that we might want to reword the top-line error message to emphasize "parameters use brackets, generally" rather than highlighting the unusual case of traits? I don't have a crisp alternative wording to propose at the moment, though.

[zackmdavis]

@estebank My only suggestion is, can we check if GenericArgs::Parenthesizeddata.inputs is empty and avoid suggesting the empty parameter list <>? I won't insist on it if it's too annoying or too much complexity for a rare case, so r=me

[estebank]

My only suggestion is, can we check if GenericArgs::Parenthesizeddata.inputs is empty and avoid suggesting the empty parameter list <>?

It makes sense to do so and should be easy enough to add.

I won't insist on it if it's too annoying or too much complexity for a rare case

I feel this is already quite a rare case to begin with, we might as well do it right :)

[estebank]

@bors r=zackmdavis

[bors]

📌 Commit 2ab6cef has been approved by zackmdavis