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rewrite suggestions intro to be less bizarrely edition/rustfix centric 

The suggestions API was introduced in April 2015
(rust-lang/rust@906a9728ff), long predating rustfix (initial commit July
2016) or editions (RFC 2052 approved September 2017).
This commit is contained in:
Zack M. Davis 2018-06-30 16:55:13 -07:00 committed by Who? Me?!
parent abccbe7139
commit a66550e48e
1 changed files with 14 additions and 10 deletions
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@ -74,17 +74,21 @@ err.emit();
## Suggestions
We would like to make edition transitions as smooth as possible. To that end,
[`rustfix`][rustfix] can use compiler suggestions to automatically fix
code. For example, we could use `rustfix` to mechanically apply the `qux`
suggestion from the previous example. However, not all suggestions are
mechanically applicable. We use the
[`span_suggestion_with_applicability`][sswa] method of `DiagnosticBuilder` to
inform the emitter of whether a suggestion is mechanically applicable or not.
This information, in turn, is outputed by rustc when the error format is
`json`, which is used by `rustfix`.
In addition to telling the user exactly _why_ their code is wrong, it's
oftentimes furthermore possible to tell them how to fix it. To this end,
`DiagnosticBuilder` offers a structured suggestions API, which formats code
suggestions pleasingly in the terminal, or (when the `--error-format json` flag
is passed) as JSON for consumption by tools, most notably the [Rust Language
Server][rls] and [`rustfix`][rustfix].
[rls]: https://github.com/rust-lang-nursery/rls
[rustfix]: https://github.com/rust-lang-nursery/rustfix
Not all suggestions should be applied mechanically. Use the
[`span_suggestion_with_applicability`][sswa] method of `DiagnosticBuilder` to
make a suggestion while providing a hint to tools whether the suggestion is
mechanically applicable or not.
[rustfix]: https://github.com/rust-lang-nursery/rustfix/
[sswa]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.DiagnosticBuilder.html#method.span_suggestion_with_applicability
For example, to make our `qux` suggestion machine-applicable, we would do: