Initial pass at expr/abstract const/s
Address comments
Switch to using a list instead of &[ty::Const], rm `AbstractConst`
Remove try_unify_abstract_consts
Update comments
Add edits
Recurse more
More edits
Prevent equating associated consts
Move failing test to ui
Changes this test from incremental to ui, and mark it as failing and a known bug.
Does not cause the compiler to ICE, so should be ok.
There are several indications that we should not ZST as a ScalarInt:
- We had two ways to have ZST valtrees, either an empty `Branch` or a `Leaf` with a ZST in it.
`ValTree::zst()` used the former, but the latter could possibly arise as well.
- Likewise, the interpreter had `Immediate::Uninit` and `Immediate::Scalar(Scalar::ZST)`.
- LLVM codegen already had to special-case ZST ScalarInt.
So instead add new ZST variants to those types that did not have other variants
which could be used for this purpose.
And likewise for the `Const::val` method.
Because its type is called `ConstKind`. Also `val` is a confusing name
because `ConstKind` is an enum with seven variants, one of which is
called `Value`. Also, this gives consistency with `TyS` and `PredicateS`
which have `kind` fields.
The commit also renames a few `Const` variables from `val` to `c`, to
avoid confusion with the `ConstKind::Value` variant.
Move a bunch of branches together into one if block, for easier reading.
Resolve comments
Attempt to make some branches unreachable [tmp]
Revert unreachable branches
Use mir constant in thir instead of ty::Const
This is blocked on https://github.com/rust-lang/rust/pull/94059 (does include its changes, the first two commits in this PR correspond to those changes) and https://github.com/rust-lang/rust/pull/93800 being reinstated (which had to be reverted). Mainly opening since `@lcnr` offered to give some feedback and maybe also for a perf-run (if necessary).
This currently contains a lot of duplication since some of the logic of `ty::Const` had to be copied to `mir::ConstantKind`, but with the introduction of valtrees a lot of that functionality will disappear from `ty::Const`.
Only the last commit contains changes that need to be reviewed here. Did leave some `FIXME` comments regarding future implementation decisions and some things that might be incorrectly implemented.
r? `@oli-obk`
