inform user where to give a type annotation

[csmoe]

should resolve #47777
previous pull request #47982 was closed because of a mistaken rebase.
r? @estebank

[rust-highfive]

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[estebank]

@csmoe could you show the rustc output both before and after for any of the compile-fail errors? Also, I think you might have to rebase against latest master (git checkout master && git pull && git checkout inform_type_annotations && git rebase master) to get the correct behavior for two ui tests (otherwise the PR won't get merged by bors).

From the look of https://github.com/rust-lang/rust/pull/48198/files#diff-c3cb6b7128630f1f0a30c553e180e677, it tackles part of #47777, but I'd still like to keep that ticket open to extend the output with more information, like pointing where the type annotation should be added (for example).

[csmoe]

@estebank
origin:

fn main() {
    let mut dirty_list = (0..5).collect();
    dirty_list.pop();
}

before

error[E0619]: the type of this value must be known in this context
 --> t.rs:3:5
  |
3 |     dirty_list.pop();
  |     ^^^^^^^^^^

error: aborting due to previous error

after this commit

error[E0282]: type annotations needed
 --> t.rs:3:5
  |
2 |     let mut dirty_list = (0..5).collect();
  |         -------------- consider giving `dirty_list` a type
3 |     dirty_list.pop();
  |     ^^^^^^^^^^ cannot infer type for `_`

error: aborting due to previous error

It’s really difficult for me to test the rustc on my laptop, I had tried about 9 hours to compile but never succeeded to build it when testing. So I just pulled this request to test my commits by bors(really sorry for the annoying failure message). Is there any way to compile with local llvm installed from linux packages repo?

I’ll update more changes about 2 days later to deal with the failure(Chinese New Year). sorry for the delay.

[estebank]

after this commit:

Love it!

It’s really difficult for me to test the rustc on my laptop, I had tried about 9 hours to compile but never succeeded to build it when testing.

That is highly unusual. It takes me about 20 minutes to compile LLVM on first pull, and after that it doesn't need to be recompiled (until pulling changes to LLVM version from the repo).

So I just pulled this request to test my commits by bors(really sorry for the annoying failure message).

I do the same sometimes when working on multiple branches (wait for travis CI to fail or pass while I keep working).

Is there any way to compile with local llvm installed from linux packages repo?

I don't know, sorry :-/

I’ll update more changes about 2 days later to deal with the failure(Chinese New Year). sorry for the delay.

Don't worry! Take your time and enjoy the holiday. I like the change, I'm looking forward to having it merged. Just ping me once you've cleared the error.

[bors]

☔ The latest upstream changes (presumably #46714) made this pull request unmergeable. Please resolve the merge conflicts.

[csmoe]

error cleared.
cc @estebank

[estebank]

@bors r+ rollup

[bors]

📌 Commit 4370a58 has been approved by estebank

[nikomatsakis]

So excited for this PR! 💯

[bors]

☔ The latest upstream changes (presumably #48399) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@csmoe I don't know your twitter handle, so I'll just drop this here:

https://twitter.com/nikomatsakis/status/966737996434366464