Sema: Fix some issues with overrides of materializeForSet

When overriding storage with a forced static dispatch materializeForSet,
the override's materializeForSet should not override the base
materializeForSet.

This is the case where a dynamic property witnesses a protocol
requirement, and Sema synthesizes a materializeForSet for it.

In this case, the synthesized materializeForSet dynamically dispatches
to the dynamic property's getter and setter, and the protocol witness
thunk directly calls the synthesized materializeForSet.

The subclass only needs to override the getter and setter in this case,
since the base class's materializeForSet will already do the right
thing.

In fact, marking it as an override exposes a problem where we cannot
serialize an xref to an imported property's materializeForSet, since
it was not created by the importer.

Author: slavapestov

lib/AST/ASTVerifier.cpp

@@ -2038,10 +2038,17 @@ class Verifier : public ASTWalker {
                  "Storage overrides but setter does not");
         if (ASD->getMaterializeForSetFunc() &&
             baseASD->getMaterializeForSetFunc() &&
-            baseASD->isSetterAccessibleFrom(ASD->getDeclContext()))
-          assert(ASD->getMaterializeForSetFunc()->getOverriddenDecl() ==
-                 baseASD->getMaterializeForSetFunc() &&
-                 "Storage override but materializeForSet does not");
+            baseASD->isSetterAccessibleFrom(ASD->getDeclContext())) {
+          if (baseASD->getMaterializeForSetFunc()->hasForcedStaticDispatch()) {
+            assert(ASD->getMaterializeForSetFunc()->getOverriddenDecl() == nullptr
+                   && "Forced static dispatch materializeForSet should not be "
+                   "overridden");
+          } else {
+            assert(ASD->getMaterializeForSetFunc()->getOverriddenDecl() ==
+                   baseASD->getMaterializeForSetFunc() &&
+                   "Storage override but materializeForSet does not");
+          }
+        }
       } else {
         if (ASD->getGetter())
           assert(!ASD->getGetter()->getOverriddenDecl() &&

lib/Sema/CodeSynthesis.cpp

@@ -872,6 +872,7 @@ static FuncDecl *addMaterializeForSet(AbstractStorageDecl *storage,
     // materializeForSet either.
     auto *baseMFS = baseASD->getMaterializeForSetFunc();
     if (baseMFS != nullptr &&
+        !baseMFS->hasForcedStaticDispatch() &&
         baseASD->isSetterAccessibleFrom(storage->getDeclContext())) {
       materializeForSet->setOverriddenDecl(baseMFS);
     }

lib/Sema/TypeCheckDecl.cpp

@@ -6532,6 +6532,13 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
             !baseASD->isSetterAccessibleFrom(overridingASD->getDeclContext()))
           return;
 
+        // A materializeForSet for an override of storage with a
+        // forced static dispatch materializeForSet is not itself an
+        // override.
+        if (kind == AccessorKind::IsMaterializeForSet &&
+            baseAccessor->hasForcedStaticDispatch())
+          return;
+
         // FIXME: Egregious hack to set an 'override' attribute.
         if (!overridingAccessor->getAttrs().hasAttribute<OverrideAttr>()) {
           auto loc = overridingASD->getOverrideLoc();

test/multifile/synthesized-accessors/materialize-for-set-1/Inputs/counter.h

@@ -0,0 +1,5 @@
+#import <Foundation/Foundation.h>
+
+@interface Counter : NSObject
+@property(readwrite) int value;
+@end

test/multifile/synthesized-accessors/materialize-for-set-1/Inputs/library.swift

@@ -0,0 +1,12 @@
+import Foundation
+import CounterFramework
+
+public protocol CounterProtocol {
+  var value: Int32 { get set }
+}
+
+extension Counter : CounterProtocol {}
+
+open class MyCounter : Counter {
+  open override var value: Int32 { didSet { } }
+}

test/multifile/synthesized-accessors/materialize-for-set-1/Inputs/module.map

@@ -0,0 +1,4 @@
+module CounterFramework {
+  header "counter.h"
+  export *
+}

test/multifile/synthesized-accessors/materialize-for-set-1/main.swift

@@ -0,0 +1,17 @@
+// RUN: %empty-directory(%t)
+
+// RUN: mkdir -p %t/onone %t/wmo
+// RUN: %target-build-swift -emit-module -emit-module-path %t/onone/library.swiftmodule -I %S/Inputs/ -module-name=library %S/Inputs/library.swift
+// RUN: %target-build-swift %S/main.swift -I %S/Inputs/ -I %t/onone/ -emit-ir > /dev/null
+
+// RUN: %target-build-swift -emit-module -emit-module-path %t/wmo/library.swiftmodule -I %S/Inputs/ -module-name=library -wmo %S/Inputs/library.swift
+// RUN: %target-build-swift %S/main.swift -I %S/Inputs/ -I %t/wmo/ -emit-ir > /dev/null
+
+// REQUIRES: objc_interop
+
+import Foundation
+import library
+
+class CustomCounter : MyCounter {
+  override var value: Int32 { didSet { } }
+}

test/multifile/synthesized-accessors/materialize-for-set-2/Inputs/counter.h

@@ -0,0 +1,5 @@
+#import <Foundation/Foundation.h>
+
+@interface Counter : NSObject
+@property(readwrite) int value;
+@end

test/multifile/synthesized-accessors/materialize-for-set-2/Inputs/library1.swift

@@ -0,0 +1,8 @@
+import Foundation
+import CounterFramework
+
+public protocol CounterProtocol {
+  var value: Int32 { get set }
+}
+
+extension Counter : CounterProtocol {}

test/multifile/synthesized-accessors/materialize-for-set-2/Inputs/library2.swift

@@ -0,0 +1,6 @@
+import Foundation
+import CounterFramework
+
+open class MyCounter : Counter {
+  open override var value: Int32 { didSet { } }
+}