Implementation of unused pattern bindings #2022, continued.
Whereas previous PR #6460 took care of parsing, and PR #6479 prepared
the stage by using _ in some test cases, this PR has the the actual
implementation, using a simple dataflow analysis.
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Co-authored-by: Burak Emir <bqe@google.com>
Co-authored-by: jonmeow <jperkins@google.com>
Propagate error state in an `extend impl` declaration out to the
enclosing scope. We can do this generically in `ApplyExtendImplAs` so we
don't have to do it explicitly in other places.
Collapse `DiagnoseExtendImplOutsideClass` into `ApplyExtendImplAs` as it
had only the one caller and is very small, so this simplifies the code,
making `ApplyExtendImplAs` a clear set of diagnostics. And push the
construction of the SpecificConstant down into `ApplyExtendImplAs` so it
is only constructed if it's needed, instead of constructing it and
throwing it away in error cases.
Ensure any error in the declaration results in the witness being an
ErrorInst so the impl will not be used in impl lookup. This simplifies
some branches by combining them into a single if statement.
This is part of #6420 which is being split up into a chain of smaller
PRs. It is based on #6467.
The main direction of this change is the edits to `destroy.carbon`
(matching in both prelude and min_prelude).
Previously there was a no-op blanket impl for `Destroy`, which hid all
missing implementations of `Destroy`. This does a few things:
- Sets up builtin aggregate destruction for struct and tuple types as
before, but also adds C++ class types and array types to the same
handling. (all as a TODO for actual implementation)
- Also maybe-unformed destruction, for now at least. (there's a chance I
may try a different approach on this, but the impl lookup wasn't working
as I'd hope in order to write it in code)
- Adds handlers for simple things that are easy to do in code: `type`,
`bool`, pointers. (because these are no-op destruction)
- Redirect `const T` destruction to `T` destruction.
This leaves as future issues:
- `partial T` destruction. (this can't be done similar to `const`
because it only works for non-`final` class types; I think `class`
definitions should just generate what's needed)
- Destruction of other prelude-provided types. (will probably come up as
we implement class destruction, that the adapted builtin type doesn't
implement `Destroy` -- but may end up special-casing that in a way that
moots it)
This moves the `&` operator from `facet_types.carbon` to
`convert.carbon` because more things need to handle type and now that
we're getting separate copy and destroy interfaces. It should be
low-cost (an interface and builtin) so hopefully this is the right
balance for complexity and re-use.
A few tests are also edited in order to focus them more on what they
intend to test, and avoid a `Destroy` dependency.
Now that included files can specify `EXTRA-ARGS`, this uses that to
handle min_prelude files. Also moves `As`/`ImplicitAs` out to a shared
file, partly because we duplicate it a few times over, partly just to
show that it works.
Also removes the `min_prelude/` subdirectories because many of these
files were touched by autoupdate regardless. I noticed one conflict for
`impl_thunk.carbon`, so renaming that one to
`impl_thunk_min_prelude.carbon`.
`GetArgReplacements` I simply noticed was unused, so removing it.
Dana Jansens