In `BuildUnaryOperator`, `GetOperatorOpFunction` is treated as
desugaring, but `PerformCompoundMemberAccess` and `PerformCall` are not.
This treats all of destruction as desugaring.
This leads to some instructions being elided, because of `GetOrAddInst`
behaviors:
> // If the instruction has a desugared location and a constant value,
returns
> // the constant value's instruction ID. Otherwise, same as AddInst.
This changes instructions that previously had a non-desugared location
to instead have a desugared location, so if they also have a constant
value then the constant value can be used directly.
This changes `Destroy` to use an interface for its implementation.
Note that this change includes a lot of test updates. Even when
`Destroy` is a no-op, it still causes code generation as part of
determining that.
Originally I was trying to use ranges to cut down the scope of this, and
to a degree I think they have. But a flipside here is that cases where
no destructors should be generated -- particularly globals -- would be
needed to completely remove destructor calls. Even for ranges, the range
can often include the destructor placement. So I've shifted
frame-of-thought a little: accept a bunch of destructor churn, because
destructors are needed and will be prevalent. The verbosity is a feature
of the design to make desugaring apparent in IR, not a bug.
import_use_generic.carbon has the comment "// We're just checking that
this doesn't crash. It's not expected to compile." Because it involves
import behavior by name, I'm not touching it. Other than that, while
maybe it's better to test with less, the `ImplicitAs` errors at best
feel difficult to understand, and at worst could be masking an issue.
People seemed receptive [on
#toolchain](https://discord.com/channels/655572317891461132/655578254970716160/1379196447827689553),
so proceeding.
For the two name conflicts, I've set it up so that there's a
"foo.carbon" and "foo_with_prelude.carbon", to indicate that the
no-prelude approach is preferred (with a shorter name).
Note min_prelude will require a little more work/thought, I want to
avoid adding `--custom-core` etc.
Jon Ross-Perkins