Clarify which kinds of MIR are allowed during which phases.
This enhances documentation with these details and extends the validator to check these requirements more thoroughly. Most of these conditions were already being checked.
There was also some disagreement between the `MirPhase` docs and validator as to what it meant for the `body.phase` field to have a certain value. This PR resolves those disagreements in favor of the `MirPhase` docs (which is what the pass manager implemented), adjusting the validator accordingly. The result is now that the `DropLowering` phase begins with the end of the elaborate drops pass, and lasts until the beginning of the generator lowring pass. This doesn't feel entirely natural to me, but as long as it's documented accurately it should be ok.
r? rust-lang/mir-opt
This enhances documentation with these details and extends the validator to check these requirements
more thoroughly. As a part of this, we add a new `Deaggregated` phase, and rename other phases so
that their names more naturally correspond to what they represent.
Remove `in_band_lifetimes` from `rustc_mir_transform`
Like #91580, this was inspired by the conversation in #44524 about possibly removing the feature from the compiler. This crate is a heavy `'tcx` user, so is a nice case study.
r? ``@petrochenkov``
Three interesting ones:
This one had the `'tcx` declared on the function, despite the trait taking a `'tcx`:
```diff
-impl Visitor<'_> for UsedLocals {
+impl<'tcx> Visitor<'tcx> for UsedLocals {
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
```
This one use in-band for one, and underscore for the other:
```diff
-pub fn remove_dead_blocks(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
+pub fn remove_dead_blocks<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
```
A spurious name, since there's no single-use-lifetime warning:
```diff
-pub fn run_passes(tcx: TyCtxt<'tcx>, body: &'mir mut Body<'tcx>, passes: &[&dyn MirPass<'tcx>]) {
+pub fn run_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, passes: &[&dyn MirPass<'tcx>]) {
```
This one is a heavy `'tcx` user.
Two interesting ones:
This one had the `'tcx` declared on the function, despite the trait taking a `'tcx`:
```diff
-impl Visitor<'_> for UsedLocals {
+impl<'tcx> Visitor<'tcx> for UsedLocals {
fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
```
This one use in-band for one, and underscore for the other:
```diff
-pub fn remove_dead_blocks(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
+pub fn remove_dead_blocks<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
```
Move `#![feature(const_precise_live_drops)]` checks earlier in the pipeline
Should mitigate the issues found during MCP on #73255.
Once this is done, we should clean up the queries a bit, since I think `mir_drops_elaborated_and_const_checked` can be merged back into `mir_promoted`.
Fixes#90770.
cc ``@rust-lang/wg-const-eval``
r? ``@nikomatsakis`` (since they reviewed #71824)
Instead we run `RemoveFalseEdges` and `RemoveUninitDrops` at the
appropriate time. The extra `SimplifyCfg` avoids visiting unreachable
blocks during `RemoveUninitDrops`.
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.
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`.
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.
