diff --git a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs index 9cd7045a0a2..89a306c6104 100644 --- a/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs +++ b/compiler/rustc_mir_transform/src/coroutine/by_move_body.rs @@ -178,7 +178,7 @@ pub(crate) fn coroutine_by_move_body_def_id<'tcx>( ), }; - ( + Some(( FieldIdx::from_usize(child_field_idx + num_args), ( FieldIdx::from_usize(parent_field_idx + num_args), @@ -186,9 +186,10 @@ pub(crate) fn coroutine_by_move_body_def_id<'tcx>( peel_deref, child_precise_captures, ), - ) + )) }, ) + .flatten() .collect(); if coroutine_kind == ty::ClosureKind::FnOnce { @@ -312,10 +313,46 @@ impl<'tcx> MutVisitor<'tcx> for MakeByMoveBody<'tcx> { self.super_place(place, context, location); } + fn visit_statement(&mut self, statement: &mut mir::Statement<'tcx>, location: mir::Location) { + // Remove fake borrows of closure captures if that capture has been + // replaced with a by-move version of that capture. + // + // For example, imagine we capture `Foo` in the parent and `&Foo` + // in the child. We will emit two fake borrows like: + // + // ``` + // _2 = &fake shallow (*(_1.0: &Foo)); + // _3 = &fake shallow (_1.0: &Foo); + // ``` + // + // However, since this transform is responsible for replacing + // `_1.0: &Foo` with `_1.0: Foo`, that makes the second fake borrow + // obsolete, and we should replace it with a nop. + // + // As a side-note, we don't actually even care about fake borrows + // here at all since they're fully a MIR borrowck artifact, and we + // don't need to borrowck by-move MIR bodies. But it's best to preserve + // as much as we can between these two bodies :) + if let mir::StatementKind::Assign(box (_, rvalue)) = &statement.kind + && let mir::Rvalue::Ref(_, mir::BorrowKind::Fake(mir::FakeBorrowKind::Shallow), place) = + rvalue + && let mir::PlaceRef { + local: ty::CAPTURE_STRUCT_LOCAL, + projection: [mir::ProjectionElem::Field(idx, _)], + } = place.as_ref() + && let Some(&(_, _, true, _)) = self.field_remapping.get(&idx) + { + statement.kind = mir::StatementKind::Nop; + } + + self.super_statement(statement, location); + } + fn visit_local_decl(&mut self, local: mir::Local, local_decl: &mut mir::LocalDecl<'tcx>) { // Replace the type of the self arg. if local == ty::CAPTURE_STRUCT_LOCAL { local_decl.ty = self.by_move_coroutine_ty; } + self.super_local_decl(local, local_decl); } } diff --git a/tests/mir-opt/async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#0}.built.after.mir b/tests/mir-opt/async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#0}.built.after.mir new file mode 100644 index 00000000000..0c8a17ff70b --- /dev/null +++ b/tests/mir-opt/async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#0}.built.after.mir @@ -0,0 +1,81 @@ +// MIR for `foo::{closure#0}::{closure#0}` after built + +fn foo::{closure#0}::{closure#0}(_1: {async closure body@$DIR/async_closure_fake_read_for_by_move.rs:12:27: 15:6}, _2: ResumeTy) -> () +yields () + { + debug _task_context => _2; + debug f => (*(_1.0: &&Foo)); + let mut _0: (); + let mut _3: &Foo; + let mut _4: &&Foo; + let mut _5: &&&Foo; + let mut _6: isize; + let mut _7: bool; + + bb0: { + PlaceMention((*(_1.0: &&Foo))); + _6 = discriminant((*(*(_1.0: &&Foo)))); + switchInt(move _6) -> [0: bb2, otherwise: bb1]; + } + + bb1: { + _0 = const (); + goto -> bb10; + } + + bb2: { + falseEdge -> [real: bb5, imaginary: bb1]; + } + + bb3: { + goto -> bb1; + } + + bb4: { + FakeRead(ForMatchedPlace(None), (*(_1.0: &&Foo))); + unreachable; + } + + bb5: { + _3 = &fake shallow (*(*(_1.0: &&Foo))); + _4 = &fake shallow (*(_1.0: &&Foo)); + _5 = &fake shallow (_1.0: &&Foo); + StorageLive(_7); + _7 = const true; + switchInt(move _7) -> [0: bb8, otherwise: bb7]; + } + + bb6: { + falseEdge -> [real: bb3, imaginary: bb1]; + } + + bb7: { + StorageDead(_7); + FakeRead(ForMatchGuard, _3); + FakeRead(ForMatchGuard, _4); + FakeRead(ForMatchGuard, _5); + _0 = const (); + goto -> bb10; + } + + bb8: { + goto -> bb9; + } + + bb9: { + StorageDead(_7); + goto -> bb6; + } + + bb10: { + drop(_1) -> [return: bb11, unwind: bb12]; + } + + bb11: { + return; + } + + bb12 (cleanup): { + resume; + } +} diff --git a/tests/mir-opt/async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#1}.built.after.mir b/tests/mir-opt/async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#1}.built.after.mir new file mode 100644 index 00000000000..bd0baddb1f8 --- /dev/null +++ b/tests/mir-opt/async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#1}.built.after.mir @@ -0,0 +1,64 @@ +// MIR for `foo::{closure#0}::{closure#1}` after built + +fn foo::{closure#0}::{closure#1}(_1: {async closure body@$DIR/async_closure_fake_read_for_by_move.rs:12:27: 15:6}, _2: ResumeTy) -> () +yields () + { + debug _task_context => _2; + debug f => (_1.0: &Foo); + let mut _0: (); + let mut _3: &Foo; + let mut _4: &&Foo; + let mut _5: &&&Foo; + let mut _6: isize; + let mut _7: bool; + + bb0: { + PlaceMention((_1.0: &Foo)); + _6 = discriminant((*(_1.0: &Foo))); + switchInt(move _6) -> [0: bb2, otherwise: bb1]; + } + + bb1: { + _0 = const (); + goto -> bb6; + } + + bb2: { + falseEdge -> [real: bb3, imaginary: bb1]; + } + + bb3: { + _3 = &fake shallow (*(_1.0: &Foo)); + _4 = &fake shallow (_1.0: &Foo); + nop; + StorageLive(_7); + _7 = const true; + switchInt(move _7) -> [0: bb5, otherwise: bb4]; + } + + bb4: { + StorageDead(_7); + FakeRead(ForMatchGuard, _3); + FakeRead(ForMatchGuard, _4); + FakeRead(ForMatchGuard, _5); + _0 = const (); + goto -> bb6; + } + + bb5: { + StorageDead(_7); + falseEdge -> [real: bb1, imaginary: bb1]; + } + + bb6: { + drop(_1) -> [return: bb7, unwind: bb8]; + } + + bb7: { + return; + } + + bb8 (cleanup): { + resume; + } +} diff --git a/tests/mir-opt/async_closure_fake_read_for_by_move.rs b/tests/mir-opt/async_closure_fake_read_for_by_move.rs new file mode 100644 index 00000000000..3c5aec94bbf --- /dev/null +++ b/tests/mir-opt/async_closure_fake_read_for_by_move.rs @@ -0,0 +1,18 @@ +//@ edition:2021 +// skip-filecheck + +enum Foo { + Bar, + Baz, +} + +// EMIT_MIR async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#0}.built.after.mir +// EMIT_MIR async_closure_fake_read_for_by_move.foo-{closure#0}-{closure#1}.built.after.mir +fn foo(f: &Foo) { + let x = async move || match f { + Foo::Bar if true => {} + _ => {} + }; +} + +fn main() {}