Tweak GenKillAnalysis.

`GenKillAnalysis` has five methods that take a transfer function arg:
- `statement_effect`
- `before_statement_effect`
- `terminator_effect`
- `before_terminator_effect`
- `call_return_effect`

All the transfer function args have type `&mut impl GenKill<Self::Idx>`,
except for `terminator_effect`, which takes the simpler `Self::Domain`.

But only the first two need to be `impl GenKill`. The other
three can all be `Self::Domain`, just like `Analysis`. So this commit
changes the last two to take `Self::Domain`, making `GenKillAnalysis`
and `Analysis` more similar.

(Another idea would be to make all these methods `impl GenKill`. But
that doesn't work: `MaybeInitializedPlaces::terminator_effect` requires
the arg be `Self::Domain` so that `self_is_unwind_dead(place, state)`
can be called on it.)

Author: nnethercote

compiler/rustc_borrowck/src/dataflow.rs

@@ -585,7 +585,7 @@ impl<'tcx> rustc_mir_dataflow::GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
 
     fn before_terminator_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _terminator: &mir::Terminator<'tcx>,
         location: Location,
     ) {
@@ -612,7 +612,7 @@ impl<'tcx> rustc_mir_dataflow::GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
 
     fn call_return_effect(
         &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
+        _trans: &mut Self::Domain,
         _block: mir::BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {

compiler/rustc_mir_dataflow/src/framework/mod.rs

@@ -248,26 +248,28 @@ pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
 
 /// A gen/kill dataflow problem.
 ///
-/// Each method in this trait has a corresponding one in `Analysis`. However, these methods only
-/// allow modification of the dataflow state via "gen" and "kill" operations. By defining transfer
-/// functions for each statement in this way, the transfer function for an entire basic block can
-/// be computed efficiently.
+/// Each method in this trait has a corresponding one in `Analysis`. However, the first two methods
+/// here only allow modification of the dataflow state via "gen" and "kill" operations. By defining
+/// transfer functions for each statement in this way, the transfer function for an entire basic
+/// block can be computed efficiently. The remaining methods match up with `Analysis` exactly.
 ///
-/// `Analysis` is automatically implemented for all implementers of `GenKillAnalysis`.
+/// `Analysis` is automatically implemented for all implementers of `GenKillAnalysis` via a blanket
+/// impl below.
 pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
     type Idx: Idx;
 
     fn domain_size(&self, body: &mir::Body<'tcx>) -> usize;
 
-    /// See `Analysis::apply_statement_effect`.
+    /// See `Analysis::apply_statement_effect`. Note how the second arg differs.
     fn statement_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
         statement: &mir::Statement<'tcx>,
         location: Location,
     );
 
-    /// See `Analysis::apply_before_statement_effect`.
+    /// See `Analysis::apply_before_statement_effect`. Note how the second arg
+    /// differs.
     fn before_statement_effect(
         &mut self,
         _trans: &mut impl GenKill<Self::Idx>,
@@ -287,7 +289,7 @@ pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
     /// See `Analysis::apply_before_terminator_effect`.
     fn before_terminator_effect(
         &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
+        _trans: &mut Self::Domain,
         _terminator: &mir::Terminator<'tcx>,
         _location: Location,
     ) {
@@ -298,7 +300,7 @@ pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
     /// See `Analysis::apply_call_return_effect`.
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         block: BasicBlock,
         return_places: CallReturnPlaces<'_, 'tcx>,
     );
@@ -313,6 +315,7 @@ pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
     }
 }
 
+// Blanket impl: any impl of `GenKillAnalysis` automatically impls `Analysis`.
 impl<'tcx, A> Analysis<'tcx> for A
 where
     A: GenKillAnalysis<'tcx>,

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -62,7 +62,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals {
 
     fn call_return_effect(
         &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
+        _trans: &mut Self::Domain,
         _block: BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {

compiler/rustc_mir_dataflow/src/impls/initialized.rs

@@ -376,7 +376,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
 
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _block: mir::BasicBlock,
         return_places: CallReturnPlaces<'_, 'tcx>,
     ) {
@@ -499,7 +499,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
 
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _block: mir::BasicBlock,
         return_places: CallReturnPlaces<'_, 'tcx>,
     ) {
@@ -617,7 +617,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for DefinitelyInitializedPlaces<'_, 'tcx> {
 
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _block: mir::BasicBlock,
         return_places: CallReturnPlaces<'_, 'tcx>,
     ) {
@@ -712,7 +712,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, 'tcx> {
 
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         block: mir::BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {

compiler/rustc_mir_dataflow/src/impls/liveness.rs

@@ -69,7 +69,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeLiveLocals {
 
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _block: mir::BasicBlock,
         return_places: CallReturnPlaces<'_, 'tcx>,
     ) {

compiler/rustc_mir_dataflow/src/impls/storage_liveness.rs

@@ -72,7 +72,7 @@ impl<'tcx, 'a> crate::GenKillAnalysis<'tcx> for MaybeStorageLive<'a> {
 
     fn call_return_effect(
         &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
+        _trans: &mut Self::Domain,
         _block: BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {
@@ -144,7 +144,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeStorageDead {
 
     fn call_return_effect(
         &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
+        _trans: &mut Self::Domain,
         _block: BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {
@@ -238,7 +238,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, 'tcx> {
 
     fn before_terminator_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         terminator: &Terminator<'tcx>,
         loc: Location,
     ) {
@@ -334,7 +334,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, 'tcx> {
 
     fn call_return_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _block: BasicBlock,
         return_places: CallReturnPlaces<'_, 'tcx>,
     ) {