Improve error message and snippet for "did you mean x"

[gavinb]

• Fixes "snippet" for "did you mean x" is not so helpful #36164
• Part of Error code list which need to be updated to new format #35233

Based on the standalone example https://is.gd/8STXMd posted by @nikomatsakis and using the third formatting option mentioned in #36164 and agreed by @jonathandturner.

Note however this does not address the question of how to handle an empty or unknown suggestion. @nikomatsakis any suggestions on how best to address that part?

[rust-highfive]

r? @nikomatsakis

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[sophiajt]

For the default cause, I'd just use an "unknown field" label

[nikomatsakis]

@gavinb nice! Can you change the test to be a UI-style test?

I agree with @jonathandturner, something generic like "unknown field" would be a good fallback label. Ideally, we'd have a test for that case too.

[gavinb]

@nikomatsakis I've added the "unknown field" handling, converted the test to UI style test and added a test specifically for the unknown field case.

[sophiajt]

Looks like adding the label means also updating a set of tests that don't expect it yet. Here's what I see from Travis:

failures:
    [compile-fail] compile-fail/attempted-access-non-fatal.rs
    [compile-fail] compile-fail/cast-rfc0401.rs
    [compile-fail] compile-fail/derived-errors/issue-30580.rs
    [compile-fail] compile-fail/issue-11004.rs
    [compile-fail] compile-fail/issue-14721.rs
    [compile-fail] compile-fail/issue-19244-2.rs
    [compile-fail] compile-fail/issue-23253.rs
    [compile-fail] compile-fail/issue-24363.rs
    [compile-fail] compile-fail/issue-24365.rs
    [compile-fail] compile-fail/issue-31011.rs
    [compile-fail] compile-fail/no-type-for-node-ice.rs
    [compile-fail] compile-fail/struct-fields-typo.rs
    [compile-fail] compile-fail/struct-pat-derived-error.rs
    [compile-fail] compile-fail/union/union-suggest-field.rs
    [compile-fail] compile-fail/unsafe-fn-autoderef.rs

[gavinb]

Ok, I'll run the complete test suite and fix up the above. (Didn't before as I was running on batteries!)

Will update PR once full build and test suite pass.

[gavinb]

@jonathandturner I went through and updated all the tests so that make check passes everything now. Once Travis has finished, this is good to go.

[GuillaumeGomez]

Thanks!

@bors: r+ rollup

[bors]

📌 Commit 99aae9b has been approved by GuillaumeGomez