SILGen: Account for abstraction differences when assigning in key path setters

Author: AnthonyLatsis

lib/SILGen/SILGenExpr.cpp

@@ -3239,6 +3239,15 @@ static SILFunction *getOrCreateKeyPathSetter(SILGenModule &SGM,
                         std::move(subscriptIndices),
                         /*index for diags*/ nullptr);
 
+  // If the assigned value will need to be reabstracted, add a reabstraction
+  // component.
+  const auto loweredSubstType = subSGF.getLoweredType(lv.getSubstFormalType());
+  if (lv.getTypeOfRValue() != loweredSubstType.getObjectType()) {
+    // Logical components always re-abstract back to the substituted type.
+    assert(lv.isLastComponentPhysical());
+    lv.addOrigToSubstComponent(loweredSubstType);
+  }
+
   subSGF.emitAssignToLValue(loc,
     RValue(subSGF, loc, propertyType, valueSubst),
     std::move(lv));

test/SILGen/keypath_accessors_reabstraction.swift

@@ -0,0 +1,28 @@
+// RUN: %target-swift-emit-silgen %s | %FileCheck %s
+
+// https://github.com/apple/swift/issues/63682
+// Test that we adjust to abstraction differences when assigning in generated
+// key path accessors.
+
+struct Foo<A> {
+  var closure: () -> A?
+}
+
+// CHECK-LABEL: sil hidden [ossa] @{{.+}}physicalFunctionValue
+func physicalFunctionValue() {
+  // CHECK: keypath $WritableKeyPath<Foo<Bool>, () -> Optional<Bool>>, (root $Foo<Bool>; settable_property $() -> Optional<Bool>,  id ##Foo.closure, getter @$[[GETTER:[_a-zA-Z0-9]+]] {{.+}}, setter @$[[SETTER:[_a-zA-Z0-9]+]]
+  let _ = \Foo<Bool>.closure
+} // CHECK: // end sil function '{{.+}}physicalFunctionValue
+
+// CHECK: sil shared [thunk] [ossa] @$[[GETTER]] : $@convention(thin) (@in_guaranteed Foo<Bool>) -> @out @callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <Optional<Bool>> {
+// CHECK: bb0([[OUT_FN:%[0-9]+]] {{.+}}):
+// CHECK: [[SRC_REABSTR:%[0-9]+]] = convert_function %{{[0-9]+}} : $@callee_guaranteed () -> @out Optional<Bool> to $@callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <Optional<Bool>>
+// CHECK-NEXT: store [[SRC_REABSTR]] to [init] [[OUT_FN]] : $*@callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <Optional<Bool>>
+// CHECK: } // end sil function '$[[GETTER]]'
+
+// CHECK: sil shared [thunk] [ossa] @$[[SETTER]] : $@convention(thin) (@in_guaranteed @callee_guaranteed @substituted <τ_0_0> () -> @out τ_0_0 for <Optional<Bool>>, @inout Foo<Bool>) -> () {
+// CHECK: bb0({{.+}}, [[FOO:%[0-9]+]] : $*Foo<Bool>):
+// CHECK: [[SRC_REABSTR:%[0-9]+]] = convert_function %{{[0-9]+}} : $@callee_guaranteed () -> @out Optional<Bool> to $@callee_guaranteed @substituted <τ_0_0> () -> @out Optional<τ_0_0> for <Bool>
+// CHECK-NEXT: [[DEST:%[0-9]+]] = struct_element_addr [[FOO]] : $*Foo<Bool>, #Foo.closure
+// CHECK-NEXT: assign [[SRC_REABSTR]] to [[DEST]] : $*@callee_guaranteed @substituted <τ_0_0> () -> @out Optional<τ_0_0> for <Bool>
+// CHECK: } // end sil function '$[[SETTER]]'