Sema: Result builder inference from dynamically replaced decl should look at getter, not storage

Author: AnthonyLatsis

lib/Sema/TypeCheckRequestFunctions.cpp

@@ -321,11 +321,25 @@ static Type inferResultBuilderType(ValueDecl *decl)  {
   // The set of matches from which we can infer result builder types.
   SmallVector<Match, 2> matches;
 
+  const auto getInferenceSourceResultBuilderType = [](ValueDecl *source) {
+    // We always infer for either a getter or freestanding function, so if the
+    // inference source is a storage declaration, inference should draw from
+    // the getter.
+    if (auto *storage = dyn_cast<AbstractStorageDecl>(source)) {
+      if (auto *getter = storage->getAccessor(AccessorKind::Get)) {
+        source = getter;
+      }
+    }
+
+    return source->getResultBuilderType();
+  };
+
   // Determine all of the conformances within the same context as
   // this declaration. If this declaration is a witness to any
   // requirement within one of those protocols that has a result builder
   // attached, use that result builder type.
-  auto addConformanceMatches = [&matches](ValueDecl *lookupDecl) {
+  auto addConformanceMatches = [&matches, &getInferenceSourceResultBuilderType](
+                                   ValueDecl *lookupDecl) {
     DeclContext *dc = lookupDecl->getDeclContext();
     auto idc = cast<IterableDeclContext>(dc->getAsDecl());
     auto conformances = idc->getLocalConformances(
@@ -341,22 +355,8 @@ static Type inferResultBuilderType(ValueDecl *decl)  {
         if (!requirement)
           continue;
 
-        Type resultBuilderType;
-        {
-          auto *inferenceSource = requirement;
-
-          // If the given declaration is a witness to a storage declaration
-          // requirement, then we are inferring for a getter and, hence, should
-          // infer from the getter requirement.
-          if (auto *storage = dyn_cast<AbstractStorageDecl>(requirement)) {
-            if (auto *getter = storage->getAccessor(AccessorKind::Get)) {
-              inferenceSource = getter;
-            }
-          }
-
-          resultBuilderType = inferenceSource->getResultBuilderType();
-        }
-
+        const Type resultBuilderType =
+            getInferenceSourceResultBuilderType(requirement);
         if (!resultBuilderType)
           continue;
 
@@ -391,7 +391,8 @@ static Type inferResultBuilderType(ValueDecl *decl)  {
 
   // Look for result builder types inferred through dynamic replacements.
   if (auto replaced = lookupDecl->getDynamicallyReplacedDecl()) {
-    if (auto resultBuilderType = replaced->getResultBuilderType()) {
+    if (auto resultBuilderType =
+            getInferenceSourceResultBuilderType(replaced)) {
       matches.push_back(
         Match::forDynamicReplacement(replaced, resultBuilderType));
     } else {

test/Constraints/result_builder_infer.swift

@@ -113,13 +113,11 @@ extension Test1 {
   var replacement_property1: Result { 1 }
   @_dynamicReplacement(for: property2)
   var replacement_property2: Result { 1 }
-  // FIXME: expected-error@-1 {{cannot convert return expression}}
 
   @_dynamicReplacement(for: subscript(subscript1:))
   subscript(replacement_subscript1 _: Int) -> Result { 1 }
   @_dynamicReplacement(for: subscript(subscript2:))
   subscript(replacement_subscript2 _: Int) -> Result { 1 }
-  // FIXME: expected-error@-1 {{cannot convert return expression}}
 }
 
 // Edge case: context is a protocol extension.
@@ -498,15 +496,13 @@ extension Test9 {
 
   @_dynamicReplacement(for: property1)
   var replacement_property1: Result { 1 }
-  // FIXME: expected-error@-1 {{cannot convert value of type 'Int' to expected argument type 'String'}}
   @_dynamicReplacement(for: property2)
   var replacement_property2: Result { 1 }
 
   @_dynamicReplacement(for: subscript(subscript1:))
   subscript(replacement_subscript1 _: Int) -> Result { 1 }
   @_dynamicReplacement(for: subscript(subscript2:))
   subscript(replacement_subscript2 _: Int) -> Result { 1 }
-  // FIXME: expected-error@-1 {{cannot convert value of type 'Int' to expected argument type 'String'}}
 }
 
 struct Test10: P_Builder_Int1, P_Builder_String {
@@ -648,13 +644,11 @@ extension Test13 {
   var replacement_property1: Result { 1 }
   @_dynamicReplacement(for: property2)
   var replacement_property2: Result { 1 }
-  // FIXME: expected-error@-1 {{cannot convert return expression}}
 
   @_dynamicReplacement(for: subscript(subscript1:))
   subscript(replacement_subscript1 _: Int) -> Result { 1 }
   @_dynamicReplacement(for: subscript(subscript2:))
   subscript(replacement_subscript2 _: Int) -> Result { 1 }
-  // FIXME: expected-error@-1 {{cannot convert return expression}}
 }
 
 struct Test14: P_Builder_Int1 {