Adjust Analysis/GenKillAnalysis interaction.

`Analysis` has six methods of note:
- `apply_statement_effect`
- `apply_before_statement_effect`
- `apply_terminator_effect`
- `apply_before_terminator_effect`
- `apply_call_return_effect`
- `apply_switch_int_edge_effects`

`GenKillAnalysis` has six similar methods of note:
- `statement_effect`
- `before_statement_effect`
- `terminator_effect`
- `before_terminator_effect`
- `call_return_effect`
- `switch_int_edge_effects`

Every `GenKillAnalysis` also implicitly impls `Analysis`, thanks to
this blanket impl:
```
impl<'tcx, A> Analysis<'tcx> for A
where
    A: GenKillAnalysis<'tcx>,
    A::Domain: GenKill<A::Idx> + BitSetExt<A::Idx>,
```
which forwards `apply_statement_effect` to `statement_effect`, and so
on.

This is a nice symmetry, but it's misleading. The latter four
`GenKillAnalysis` methods (`terminator_effect`, ...) are only called
from the latter four `Analysis` methods (`apply_terminator_effect`,
...). In reality, to implement a `GenKillAnalysis` you want to implement
the first two `GenKillAnalysis` methods (which take `impl GenKill` args)
and the latter four `Analysis` methods (which can take `Self::Domain`
args).

This commit adjusts things accordingly.
- The latter four methods in `GenKillAnalysis` are removed.
- The blanket impl of `Analysis` for any type implementing
  `GenKillAnalysis` is removed.
- Each gen-kill analysis now implements the two `GenKillAnalysis`
  methods and the four latter `Analysis` methods.
- Each gen-kill analysis also implicitly implements the first two
  `Analysis` methods by using new macros
  `fn_apply_before_statement_effect_gen_kill!` and
  `fn_apply_statement_effect_gen_kill!` that just define a method that
  forwards on to the corresponding `GenKillAnalysis` method.

Overall this is a little less code and I find the whole structure easier
to understand.

Author: nnethercote

compiler/rustc_borrowck/src/dataflow.rs

@@ -10,8 +10,8 @@ use rustc_middle::ty::RegionVid;
 use rustc_middle::ty::TyCtxt;
 use rustc_mir_dataflow::impls::{EverInitializedPlaces, MaybeUninitializedPlaces};
 use rustc_mir_dataflow::ResultsVisitable;
-use rustc_mir_dataflow::{self, fmt::DebugWithContext, GenKill};
-use rustc_mir_dataflow::{Analysis, Direction, Results};
+use rustc_mir_dataflow::{self, fmt::DebugWithContext, GenKill, GenKillAnalysis};
+use rustc_mir_dataflow::{Analysis, AnalysisDomain, Direction, Results};
 use std::fmt;
 
 use crate::{places_conflict, BorrowSet, PlaceConflictBias, PlaceExt, RegionInferenceContext};
@@ -506,7 +506,7 @@ impl<'mir, 'tcx> Borrows<'mir, 'tcx> {
     }
 }
 
-impl<'tcx> rustc_mir_dataflow::AnalysisDomain<'tcx> for Borrows<'_, 'tcx> {
+impl<'tcx> AnalysisDomain<'tcx> for Borrows<'_, 'tcx> {
     type Domain = BitSet<BorrowIndex>;
 
     const NAME: &'static str = "borrows";
@@ -529,7 +529,7 @@ impl<'tcx> rustc_mir_dataflow::AnalysisDomain<'tcx> for Borrows<'_, 'tcx> {
 ///   region stops containing the CFG points reachable from the issuing location.
 /// - we also kill loans of conflicting places when overwriting a shared path: e.g. borrows of
 ///   `a.b.c` when `a` is overwritten.
-impl<'tcx> rustc_mir_dataflow::GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
+impl<'tcx> GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
     type Idx = BorrowIndex;
 
     fn domain_size(&self, _: &mir::Body<'tcx>) -> usize {
@@ -592,17 +592,23 @@ impl<'tcx> rustc_mir_dataflow::GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
             | mir::StatementKind::Nop => {}
         }
     }
+}
+
+impl<'tcx> Analysis<'tcx> for Borrows<'_, 'tcx> {
+    rustc_mir_dataflow::fn_apply_before_statement_effect_gen_kill!();
+
+    rustc_mir_dataflow::fn_apply_statement_effect_gen_kill!();
 
-    fn before_terminator_effect(
+    fn apply_before_terminator_effect(
         &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
+        trans: &mut Self::Domain,
         _terminator: &mir::Terminator<'tcx>,
         location: Location,
     ) {
         self.kill_loans_out_of_scope_at_location(trans, location);
     }
 
-    fn terminator_effect<'mir>(
+    fn apply_terminator_effect<'mir>(
         &mut self,
         trans: &mut Self::Domain,
         terminator: &'mir mir::Terminator<'tcx>,
@@ -620,9 +626,9 @@ impl<'tcx> rustc_mir_dataflow::GenKillAnalysis<'tcx> for Borrows<'_, 'tcx> {
         terminator.edges()
     }
 
-    fn call_return_effect(
+    fn apply_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

@@ -253,7 +253,9 @@ pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
 /// functions for each statement in this way, the transfer function for an entire basic block can
 /// be computed efficiently.
 ///
-/// `Analysis` is automatically implemented for all implementers of `GenKillAnalysis`.
+/// Use `fn_apply_statement_effect_gen_kill!` and (optionally)
+/// `fn_apply_before_statement_effect_gen_kill!` to simplify the definition of
+/// `Analysis` for analyses that also impl `GenKillAnalysis`.
 pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
     type Idx: Idx;
 
@@ -275,117 +277,40 @@ pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
         _location: Location,
     ) {
     }
-
-    /// See `Analysis::apply_terminator_effect`.
-    fn terminator_effect<'mir>(
-        &mut self,
-        trans: &mut Self::Domain,
-        terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) -> TerminatorEdges<'mir, 'tcx>;
-
-    /// See `Analysis::apply_before_terminator_effect`.
-    fn before_terminator_effect(
-        &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
-        _terminator: &mir::Terminator<'tcx>,
-        _location: Location,
-    ) {
-    }
-
-    /* Edge-specific effects */
-
-    /// See `Analysis::apply_call_return_effect`.
-    fn call_return_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        block: BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    );
-
-    /// See `Analysis::apply_switch_int_edge_effects`.
-    fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
-        &mut self,
-        _block: BasicBlock,
-        _discr: &mir::Operand<'tcx>,
-        _edge_effects: &mut impl SwitchIntEdgeEffects<G>,
-    ) {
-    }
 }
 
-impl<'tcx, A> Analysis<'tcx> for A
-where
-    A: GenKillAnalysis<'tcx>,
-    A::Domain: GenKill<A::Idx> + BitSetExt<A::Idx>,
-{
-    fn apply_statement_effect(
-        &mut self,
-        state: &mut A::Domain,
-        statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        self.statement_effect(state, statement, location);
-    }
-
-    fn apply_before_statement_effect(
-        &mut self,
-        state: &mut A::Domain,
-        statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        self.before_statement_effect(state, statement, location);
-    }
-
-    fn apply_terminator_effect<'mir>(
-        &mut self,
-        state: &mut A::Domain,
-        terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) -> TerminatorEdges<'mir, 'tcx> {
-        self.terminator_effect(state, terminator, location)
-    }
-
-    fn apply_before_terminator_effect(
-        &mut self,
-        state: &mut A::Domain,
-        terminator: &mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        self.before_terminator_effect(state, terminator, location);
-    }
-
-    /* Edge-specific effects */
-
-    fn apply_call_return_effect(
-        &mut self,
-        state: &mut A::Domain,
-        block: BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-        self.call_return_effect(state, block, return_places);
-    }
-
-    fn apply_switch_int_edge_effects(
-        &mut self,
-        block: BasicBlock,
-        discr: &mir::Operand<'tcx>,
-        edge_effects: &mut impl SwitchIntEdgeEffects<A::Domain>,
-    ) {
-        self.switch_int_edge_effects(block, discr, edge_effects);
-    }
+/// Use this to define `Analysis::apply_before_statement_effect` in types that
+/// impl both `Analysis` and `GenKillAnalysis`. It delegates to
+/// `GenKillAnalysis::apply_before_statement_effect`.
+#[macro_export]
+macro_rules! fn_apply_before_statement_effect_gen_kill {
+    () => {
+        fn apply_before_statement_effect(
+            &mut self,
+            trans: &mut Self::Domain,
+            stmt: &rustc_middle::mir::Statement<'tcx>,
+            location: Location,
+        ) {
+            self.before_statement_effect(trans, stmt, location);
+        }
+    };
+}
 
-    /* Extension methods */
-    #[inline]
-    fn into_engine<'mir>(
-        self,
-        tcx: TyCtxt<'tcx>,
-        body: &'mir mir::Body<'tcx>,
-    ) -> Engine<'mir, 'tcx, Self>
-    where
-        Self: Sized,
-    {
-        Engine::new_gen_kill(tcx, body, self)
-    }
+/// Use this to define `Analysis::apply_statement_effect` in types that impl
+/// both `Analysis` and `GenKillAnalysis`. It just delegates to
+/// `GenKillAnalysis::apply_statement_effect`.
+#[macro_export]
+macro_rules! fn_apply_statement_effect_gen_kill {
+    () => {
+        fn apply_statement_effect(
+            &mut self,
+            trans: &mut Self::Domain,
+            stmt: &rustc_middle::mir::Statement<'tcx>,
+            location: Location,
+        ) {
+            self.statement_effect(trans, stmt, location);
+        }
+    };
 }
 
 /// The legal operations for a transfer function in a gen/kill problem.

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -2,7 +2,7 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 
-use crate::{AnalysisDomain, GenKill, GenKillAnalysis};
+use crate::{Analysis, AnalysisDomain, GenKill, GenKillAnalysis};
 
 /// A dataflow analysis that tracks whether a pointer or reference could possibly exist that points
 /// to a given local. This analysis ignores fake borrows, so it should not be used by
@@ -49,8 +49,12 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals {
     ) {
         self.transfer_function(trans).visit_statement(statement, location);
     }
+}
+
+impl<'tcx> Analysis<'tcx> for MaybeBorrowedLocals {
+    crate::fn_apply_statement_effect_gen_kill!();
 
-    fn terminator_effect<'mir>(
+    fn apply_terminator_effect<'mir>(
         &mut self,
         trans: &mut Self::Domain,
         terminator: &'mir Terminator<'tcx>,
@@ -60,9 +64,9 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals {
         terminator.edges()
     }
 
-    fn call_return_effect(
+    fn apply_call_return_effect(
         &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
+        _trans: &mut Self::Domain,
         _block: BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {