Fix bad error message with ::< in types

[mcarton]

Fix #36116.

Before:

error: expected identifier, found `<`
  --> src/test/compile-fail/issue-36116.rs:16:52
   |
16 |     let f = Some(Foo { _a: 42 }).map(|a| a as Foo::<i32>);
   |                                                    ^

error: chained comparison operators require parentheses
  --> src/test/compile-fail/issue-36116.rs:16:52
   |
16 |     let f = Some(Foo { _a: 42 }).map(|a| a as Foo::<i32>);
   |                                                    ^^^^^^
   |
   = help: use `::<...>` instead of `<...>` if you meant to specify type arguments

error: expected expression, found `)`
  --> src/test/compile-fail/issue-36116.rs:16:57
   |
16 |     let f = Some(Foo { _a: 42 }).map(|a| a as Foo::<i32>);
   |                                                         ^

error: expected identifier, found `<`
  --> src/test/compile-fail/issue-36116.rs:20:17
   |
20 |     let g: Foo::<i32> = Foo { _a: 42 };
   |                 ^

error: aborting due to 5 previous errors

After:

error: unexpected token: `::`
  --> src/test/compile-fail/issue-36116.rs:16:50
   |
16 |     let f = Some(Foo { _a: 42 }).map(|a| a as Foo::<i32>);
   |                                                  ^^
   |
   = help: use `<...>` instead of `::<...>` if you meant to specify type arguments

error: unexpected token: `::`
  --> src/test/compile-fail/issue-36116.rs:20:15
   |
20 |     let g: Foo::<i32> = Foo { _a: 42 };
   |               ^^
   |
   = help: use `<...>` instead of `::<...>` if you meant to specify type arguments

error: aborting due to 2 previous errors

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @pnkfelix (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[pnkfelix]

(travis failure seemed spurious; i'm giving it another shot and also starting a review.)

[pnkfelix]

stylistically I don't think we put line breaks between the if and the condition expression in cases like this.

[pnkfelix]

stylistically I think we tend to separate the arrow (the ^ and the |) and the ERROR/WARN by putting a space between them.

[pnkfelix]

These changes seem fine to me. I had stylistic nits that would be nice to address.

[pnkfelix]

In other words, r=me once nits are addressed.

[mcarton]

Addressed nits.

[cramertj]

@pnkfelix Any reason this hasn't been merged yet? I've gotten this error a few times, and this change would make the solution much clearer.

[pnkfelix]

@bors r+ rollup

[bors]

📌 Commit 17bbcac has been approved by pnkfelix

[GuillaumeGomez]

It seems your code fails:

error: attempted access of field `last_span` on type `&mut parse::parser::Parser<'a>`, but no field with that name was found
    --> ../src/libsyntax/parse/parser.rs:1762:33
     |
1762 |                 let last_span = self.last_span;
     |                                 ^^^^^^^^^^^^^^

error: aborting due to previous error

Please update your code and I'll re-r+ it.

@bors: r-

[mcarton]

@GuillaumeGomez done. Thanks for pointing that out, that field was renamed in #36470.

[pnkfelix]

@bors r+ rollup

[bors]

📌 Commit 368f435 has been approved by pnkfelix

[pnkfelix]

@bors r-

[pnkfelix]

It has been pointed out that this commit series needs revision. It should be rebased (to remove the merge commit) and squashed into a smaller series of commits, e.g. One commit maybe

[mcarton]

No problem, done.

[pnkfelix]

Great, thanks for your patience and perseverance @mcarton

[pnkfelix]

@bors r+ rollup

[bors]

📌 Commit f7cc6dc has been approved by pnkfelix