Diagnostic rendering was part of the data model: `Loc::FormatLocation`
and
`Loc::FormatSnippet` wrote plain text to a stream, so no capability,
color, or
terminal width could reach them.
A diagnostic is now one message with labels, contexts, and location
information
attached, and `Diagnostics::Renderer` draws it into a
`Terminal::Buffer`. The
design is in `toolchain/docs/diagnostics_rendering.md` (#7668),
authoring in
`toolchain/docs/diagnostics.md`.
Before:
```
example.carbon:6:3: error: 1 argument passed to function expecting 0 arguments
Run0(1);
^~~~~~~
example.carbon:3:1: note: calling function declared here
fn Run0() {}
^~~~~~~~~~~
```
After:
```
error: 1 argument passed to function expecting 0 arguments
╭─┤ example.carbon:6:3
┆
3 │ fn Run0() {}
· ─────┬─────
· ╰──┤ calling function declared here
┆
-> 6 │ Run0(1);
· ───────
╰────────────
```
`--no-diagnostic-snippets` gives a compact form, `example.carbon:6:3-9`.
File
tests use it; the rendering tests under `toolchain/diagnostics/testdata`
ask for
snippets.
C++ interop diagnostics are data now rather than text Clang drew:
`SemIR::ClangSourceLocId` names a `clang::SourceRange`, and a Clang
location is
marked as the point it names.
`StreamConsumer` moves to a `:renderer` target that `:emitter` does not
depend
on, keeping `common/terminal` out of `consumer.h`. Capabilities come
from the
file behind the error stream, so tests get plain ASCII.
`renderer_fuzzer` draws diagnostics built from fuzzer bytes with every
capability combination, since a shape the renderer doesn't expect must
never be
why the compiler dies while reporting a problem.
TODOs mark the follow-ups: line weights and crossing lines, wrapping
that keeps
a quoted type whole, and ordering diagnostics that share a byte offset.
Also: `IncorrectExtension`'s hint moves into its message, since its note
had no
location of its own, and `strip_noise` in `check_diagnostics.py` blanks
multi-line `#define`s instead of deleting them.
Assisted-by: Claude Code
Split the diagnostic emitter into a separate emitter (regietered with
Clang) and listener (registered with the emitter). The purpose of this
split is to make the Clang emitter not depend on the `Check::Context`,
so that we can use it, and hence the same Clang instance, with multiple
`Check::Context`s. A fallback listener is registered to collect and emit
any diagnostics produced while we don't have a `Check::Context`
registered with the emitter.
Assisted-by: Gemini via Antigravity
Include notes listing the candidates and explaining why they didn't
work. Rather than duplicating the (substantial) logic for this, use the
Clang machinery to generate these diagnostics.
In order to support this, add a mechanism to map `SemIR::LocId`s to
`clang::SourceLocation`s. This works by creating source buffers in Clang
that refer into the Carbon source file so that `SourceLocation`s can
point into them.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Chandler Carruth
Richard Smith
