Remove `mir::CastKind::Misc`
As discussed in #97649 `mir::CastKind::Misc` is not clear, this PR addresses that by creating a new enum variant for every valid cast.
r? ````@oli-obk````
On later stages, the feature is already stable.
Result of running:
rg -l "feature.let_else" compiler/ src/librustdoc/ library/ | xargs sed -s -i "s#\\[feature.let_else#\\[cfg_attr\\(bootstrap, feature\\(let_else\\)#"
Replace `Body::basic_blocks()` with field access
Since the refactoring in #98930, it is possible to borrow the basic blocks
independently from other parts of MIR by accessing the `basic_blocks` field
directly.
Replace unnecessary `Body::basic_blocks()` method with a direct field access,
which has an additional benefit of borrowing the basic blocks only.
A resume place is evaluated and assigned to only after a yield
terminator resumes. Ensure that locals used when evaluating the
resume place are live across the yield.
Remove the unused StableSet and StableMap types from rustc_data_structures.
The current implementation is not "stable" in the same sense that `HashStable` and `StableHasher` are stable, i.e. across compilation sessions. So, in my opinion, it's better to remove those types (which are basically unused anyway) than to give the wrong impression that these are safe for incr. comp.
I plan to provide new "stable" collection types soon that can be used to replace `FxHashMap` and `FxHashSet` in query results (see [draft](69d03ac7a7)). It's unsound that `HashMap` and `HashSet` implement `HashStable` (see https://github.com/rust-lang/rust/issues/98890 for a recent P-critical bug caused by this) -- so we should make some progress there.
Allow destructuring opaque types in their defining scopes
fixes#96572
Before this PR, the following code snippet failed with an incomprehensible error, and similar code just ICEd in mir borrowck.
```rust
type T = impl Copy;
let foo: T = (1u32, 2u32);
let (a, b) = foo;
```
The problem was that the last line created MIR projections of the form `foo.0` and `foo.1`, but `foo`'s type is `T`, which doesn't have fields (only its hidden type does). But the pattern supplies enough type information (a tuple of two different inference types) to bind a hidden type.
Edit `rustc_mir_dataflow::framework::lattice::FlatSet` docs
Cosmetic improvements. Adds a paragraph break, and
ellipses to signify arbitrary size of a flat set.
