What this really does is avoids shadowing names, so that we can
comfortable have things like `Check::DiagnosticEmitter` or
`Check::DiagnosticLoc` without shadowing being a concern.
Note, down this path I'm also thinking about:
- Renaming misc DiagnosticConsumer/DiagnosticEmitter classes, possibly
just to DiagnosticConsumer/DiagnosticEmitter (so
`Check::DiagnosticEmitter` instead of `SemIRLocDiagnosticEmitter`).
- Dropping `Diagnostic` from `Emitter::DiagnosticBuilder`.
- But not for `Check::DiagnosticBuilder`, because `Check::Builder` would
be ambiguous.
- Renaming diagnostics/diagnostic_* to drop "diagnostic".
[Discussion about SemIRLoc ->
DiagnosticLoc](https://discord.com/channels/655572317891461132/655578254970716160/1353771570463768698)
reminded me of this (in particular the older [Check::DiagnosticBuilder
discussion](https://discord.com/channels/655572317891461132/655578254970716160/1344363562608627763)),
but I'd only do that rename if there's matching consensus about a path
forward where we keep SemIRLoc, and in a way that it's only ever used
for diagnostics (the divergence from which is at the root of current
LocId discussion).
I'm trying to keep that separate from a namespace addition for clarity.
Also makes the style guide explicitly comment on void, but this was the
intent IIRC because it matches Carbon's `-> ()` (and "always" versus
"except for void", which we definitely went back and forth on).
Includes adjusting function pointers, which I definitely forget this
syntax works sometimes.
Excludes utils/tree_sitter/src/scanner.c because it claims to be C, but
really we should probably fix that to be cpp.
Omit the `note: ` prefix and the snippet from the "in import" note that
precedes a diagnostic.
This makes our diagnostic output more closely match that of Clang and
GCC.
On #3792 it was requested to put context-related diagnostic messages
prior to the diagnostic error. In order to support that, remove the
distinction that an error needs to come first on DiagnosticMessage.
I wanted to choose one or the other. I think some code has been using
each from early on. We're predominately using `filename`, so
consolidating on that. This conveniently matches the [Google dev doc
style guide](https://developers.google.com/style/word-list#filename)
(which we use for docs) which says "filename: Not file name".
In toolchain:
```
╚╡git grep file_name . | wc -l
35
╚╡git grep filename . | wc -l
489
```
Followup for #2490
The switch of DiagnosticMessage to have DiagnosticMessage means we don't need to use unique_ptr. This means that copy constructors are implicit again and don't need to be avoided, but per discussion still keeping with moves. Comments on HandleDiagnostic try to capture the use of moves there.
I'm keeping DiagnosticLevel at the top-level, and adding some checking that notes are actually Notes.
Also, adding MakeMessage to unify some of the logic (this has particularly been bugging me around format_fn, and I ran into it here because of the Diagnostic -> DiagnosticMessage change). The addition of NoTypeDeduction is intended to avoid some duplicative comments that'd been piling up.
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Thomas Köppe
Jon Ross-Perkins
Richard Smith
Jon Meow