Otherwise dataflow state will propagate along false edges and cause
things to be marked as maybe init unnecessarily. These should be
separate, since `SimplifyBranches` also makes `if true {} else {}` into
a `goto`, which means we wouldn't lint anything in the `else` block.
Previously for enums using the `Variants::Single` layout, the variant
index was being confused with its discriminant. For example, in the case
of `enum E { A = 1 }`.
Use `discriminant_for_variant` to avoid the issue.
The change is limited to the iteration over indices instead of using
`basic_blocks_mut()` directly, in the case the previous implementation
intentionally avoided invalidating the caches stored in MIR body.
Remove hir::map::blocks and use FnKind instead
The principal tool is `FnLikeNode`, which is not often used and can be easily implemented using `rustc_hir::intravisit::FnKind`.
Adopt let_else across the compiler
This performs a substitution of code following the pattern:
```
let <id> = if let <pat> = ... { identity } else { ... : ! };
```
To simplify it to:
```
let <pat> = ... { identity } else { ... : ! };
```
By adopting the `let_else` feature (cc #87335).
The PR also updates the syn crate because the currently used version of the crate doesn't support `let_else` syntax yet.
Note: Generally I'm the person who *removes* usages of unstable features from the compiler, not adds more usages of them, but in this instance I think it hopefully helps the feature get stabilized sooner and in a better state. I have written a [comment](https://github.com/rust-lang/rust/issues/87335#issuecomment-944846205) on the tracking issue about my experience and what I feel could be improved before stabilization of `let_else`.
Index and hash HIR as part of lowering
Part of https://github.com/rust-lang/rust/pull/88186
~Based on https://github.com/rust-lang/rust/pull/88880 (see merge commit).~
Once HIR is lowered, it is later indexed by the `index_hir` query and hashed for `crate_hash`. This PR moves those post-processing steps to lowering itself. As a side objective, the HIR crate data structure is refactored as an `IndexVec<LocalDefId, Option<OwnerInfo<'hir>>>` where `OwnerInfo` stores all the relevant information for an HIR owner.
r? `@michaelwoerister`
cc `@petrochenkov`
This performs a substitution of code following the pattern:
let <id> = if let <pat> = ... { identity } else { ... : ! };
To simplify it to:
let <pat> = ... { identity } else { ... : ! };
By adopting the let_else feature.
Stabilize `const_panic`
Closes#51999
FCP completed in #89006
```@rustbot``` label +A-const-eval +A-const-fn +T-lang
cc ```@oli-obk``` for review (not `r?`'ing as not on lang team)
Rework HIR API to make invocations of the hir_crate query harder.
`hir_crate` forces the recomputation of queries that depend on it.
This PR aims at avoiding useless invocations of `hir_crate` by making dependent code go through `tcx.hir()`.
Correct caller/callsite confusion in inliner message
`callee_body` is the MIR `Body` for the `callsite.callee` so this message basically says `"Inline {bar span} into bar"` when it should say `"Inline bar into foo"`.
Extracted out of #82280
