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Auto merge of #101986 - WaffleLapkin:move_lint_note_to_the_bottom, r=estebank

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Move lint level source explanation to the bottom

So, uhhhhh

r? `@estebank`

## User-facing change

"note: `#[warn(...)]` on by default" and such are moved to the bottom of the diagnostic:
```diff
-   = note: `#[warn(unsupported_calling_conventions)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
+   = note: `#[warn(unsupported_calling_conventions)]` on by default
```

Why warning is enabled is the least important thing, so it shouldn't be the first note the user reads, IMO.

## Developer-facing change

`struct_span_lint` and similar methods have a different signature.

Before: `..., impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>)`
After: `..., impl Into<DiagnosticMessage>, impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>) -> &'b mut DiagnosticBuilder<'a, ()>`

The reason for this is that `struct_span_lint` needs to edit the diagnostic _after_ `decorate` closure is called. This also makes lint code a little bit nicer in my opinion.

Another option is to use `impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>) -> DiagnosticBuilder<'a, ()>` altough I don't _really_ see reasons to do `let lint = lint.build(message)` everywhere.

## Subtle problem

By moving the message outside of the closure (that may not be called if the lint is disabled) `format!(...)` is executed earlier, possibly formatting `Ty` which may call a query that trims paths that crashes the compiler if there were no warnings...

I don't think it's that big of a deal, considering that we move from `format!(...)` to `fluent` (which is lazy by-default) anyway, however this required adding a workaround which is unfortunate.

## P.S.

I'm sorry, I do not how to make this PR smaller/easier to review. Changes to the lint API affect SO MUCH 😢
This commit is contained in:
bors 2022-10-01 10:44:25 +00:00
commit 744e397d88
827 changed files with 3370 additions and 3210 deletions
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24
compiler/rustc_errors/src/diagnostic_builder.rs
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@ -642,27 +642,3 @@ macro_rules! struct_span_err {
macro_rules! error_code {
($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};
}
/// Wrapper around a `DiagnosticBuilder` for creating lints.
pub struct LintDiagnosticBuilder<'a, G: EmissionGuarantee>(DiagnosticBuilder<'a, G>);
impl<'a, G: EmissionGuarantee> LintDiagnosticBuilder<'a, G> {
#[rustc_lint_diagnostics]
/// Return the inner `DiagnosticBuilder`, first setting the primary message to `msg`.
pub fn build(mut self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'a, G> {
self.0.set_primary_message(msg);
self.0.set_is_lint();
self.0
}
/// Create a `LintDiagnosticBuilder` from some existing `DiagnosticBuilder`.
pub fn new(err: DiagnosticBuilder<'a, G>) -> LintDiagnosticBuilder<'a, G> {
LintDiagnosticBuilder(err)
}
}
impl<'a> LintDiagnosticBuilder<'a, ErrorGuaranteed> {
pub fn forget_guarantee(self) -> LintDiagnosticBuilder<'a, ()> {
LintDiagnosticBuilder(self.0.forget_guarantee())
}
}