Signed-off-by: hi-rustin <rustin.liu@gmail.com>

This is less elegant in some ways, since we no longer visit a BCB's spans as a
batch, but will make it much easier to add support for other kinds of coverage
mapping regions (e.g. branch regions or gap regions).

They have one and two call sites respectively, and they just make the
code harder to read.

Errors in `DiagCtxtInner::emit_diagnostic` are never set to
`Level::Bug`, because the condition never succeeds, because
`self.treat_err_as_bug()` is called *before* the error counts are
incremented.

This commit switches to `self.treat_next_err_as_bug()`, fixing the
problem. This changes the error message output to actually say "internal
compiler error".

No point computing `warnings` and `errors` if we're going to return
early before they're used.

… consideration.

It seems very wrong to have a `-Ztreat-err-as-bug` check here before the
error is even emitted.

Once that's done:
- `into_diagnostic` is infallible, so its return type doesn't need the
  `Option`;
- the `&'a DiagCtxt` also isn't needed, because only one callsite uses
  it, and it already have access to it via `self.dcx`;
- the comments about dcx disabling buffering are no longer true, this is
  unconditional now;
- and the `debug!` seems unnecessary... the comment greatly overstates
  its importance because few diagnostics come through `into_diagnostic`,
  and `-Ztrack-diagnostics` exists anyway.

Each of these has a single call site: `source_file_to_parser`,
`try_file_to_source_file`, `file_to_source_file`. Having them separate
just makes the code longer and harder to read.

Also, `maybe_file_to_stream` doesn't need to be `pub`.

It's a little more concise, and the standard way to do it.

This requires cancelling the "secondary" errors when they're not
emitted, to prevent panics due to unconsumed `DiagnosticBuilder`s.

But we can't easily switch from `Vec<Diagnostic>` to
`Vec<DiagnosticBuilder<G>>` because there's a mix of errors and warnings
which result in different `G` types. So we must make
`DiagnosticBuilder::into_diagnostic` public, but that's ok, and it will
get more use in subsequent commits.

Two different lifetimes are conflated. This doesn't matter right now,
but needs to be fixed for the next commit to work. And the more
descriptive lifetime names make the code easier to read.

One consequence is that errors returned by
`maybe_new_parser_from_source_str` now must be consumed, so a bunch of
places that previously ignored those errors now cancel them. (Most of
them explicitly dropped the errors before. I guess that was to indicate
"we are explicitly ignoring these", though I'm not 100% sure.)

All its uses have been removed.

Signed-off-by: hi-rustin <rustin.liu@gmail.com>

…avidtwco

annotate-snippets: update to 0.10

Ports `annotate-snippets` to 0.10, temporary dupes versions; other crates left that depends on 0.9 is `ui_test` and `rustfmt`.

…2, r=estebank

Silence some follow-up errors [2/x]

this is one piece of the requested cleanups from rust-lang#117449

the `type_of` query frequently uses astconv to convert a `hir::Ty` to a `ty::Ty`. This process is infallible, but may produce errors as it goes. All the error reporting sites that had access to the `ItemCtxt` are now tainting it, causing `type_of` to return a `ty::Error` instead of anything else.

…line, r=ChrisDenton

chore: remove unnecessary blank line

It seems no need to add an unnecessary line here.

…uffer, r=oli-obk

Remove `DiagnosticBuilder::buffer`

`DiagnosticBuilder::buffer` doesn't do much, and part of what it does (for `-Ztreat-err-as-bug`) it shouldn't.

This PR strips it back, replaces its uses, and finally removes it, making a few cleanups in the vicinity along the way.

r? ``@oli-obk``

coverage: Add enums to accommodate other kinds of coverage mappings

Extracted from  rust-lang#118305.

LLVM supports several different kinds of coverage mapping regions, but currently we only ever emit ordinary “code” regions.  This PR performs the plumbing required to add other kinds of regions as enum variants, but does not add any specific variants other than `Code`.

The main motivation for this change is branch coverage, but it will also allow separate experimentation with gap regions and skipped regions, which might help in producing more accurate and useful coverage reports.

---

``@rustbot`` label +A-code-coverage

rint: further doc tweaks

r? ``@nagisa``

…rors

give const-err4 a more descriptive name

Also, doesn't look like this still needs to be per-bitwidth

r? ``@oli-obk``

rustfmt.toml: don't ignore just any tests path, only root one

Previously ignored any `tests` path, now only /tests at repo root.

For reference, https://git-scm.com/docs/gitignore#_pattern_format