Cascade doc comments from protocol requirements to extensions

lib/AST/DocComment.cpp

@@ -392,6 +392,47 @@ getAnyBaseClassDocComment(swift::markup::MarkupContext &MC,
   return None;
 }
 
+static Optional<DocComment *>
+getProtocolRequirementDocComment(swift::markup::MarkupContext &MC,
+                                 const ProtocolDecl *ProtoExt,
+                                 const Decl *D) {
+
+  auto getSingleRequirementWithNonemptyDoc = [](const ProtocolDecl *P,
+                                                const ValueDecl *VD)
+    -> const ValueDecl * {
+      SmallVector<ValueDecl *, 2> Members;
+      P->lookupQualified(P->getType(), VD->getFullName(),
+                         NLOptions::NL_ProtocolMembers,
+                         /*resolver=*/nullptr, Members);
+    SmallVector<const ValueDecl *, 1> ProtocolRequirements;
+    for (auto Member : Members)
+      if (!Member->isDefinition())
+        ProtocolRequirements.push_back(Member);
+
+    if (ProtocolRequirements.size() == 1) {
+      auto Requirement = ProtocolRequirements.front();
+      if (!Requirement->getRawComment().isEmpty())
+        return Requirement;
+    }
+
+    return nullptr;
+  };
+
+  if (const auto *VD = dyn_cast<ValueDecl>(D)) {
+    SmallVector<const ValueDecl *, 4> RequirementsWithDocs;
+    if (auto Requirement = getSingleRequirementWithNonemptyDoc(ProtoExt, VD))
+      RequirementsWithDocs.push_back(Requirement);
+
+    for (auto Proto : ProtoExt->getInheritedProtocols(/*resolver=*/nullptr))
+      if (auto Requirement = getSingleRequirementWithNonemptyDoc(Proto, VD))
+        RequirementsWithDocs.push_back(Requirement);
+
+    if (RequirementsWithDocs.size() == 1)
+      return getSingleDocComment(MC, RequirementsWithDocs.front());
+  }
+  return None;
+}
+
 Optional<DocComment *>
 swift::getCascadingDocComment(swift::markup::MarkupContext &MC, const Decl *D) {
   auto Doc = getSingleDocComment(MC, D);
@@ -404,8 +445,9 @@ swift::getCascadingDocComment(swift::markup::MarkupContext &MC, const Decl *D) {
     if (auto BaseClassDoc = getAnyBaseClassDocComment(MC, CD, D))
       return BaseClassDoc;
 
-  // FIXME: Look at protocol requirement declarations if a protocol
-  // extension implementation doesn't have a doc comment.
+  if (const auto *PE = D->getDeclContext()->getAsProtocolExtensionContext())
+    if (auto ReqDoc = getProtocolRequirementDocComment(MC, PE, D))
+      return ReqDoc;
 
   return None;
 }

test/IDE/comment_inherited_protocol.swift

@@ -0,0 +1,72 @@
+// RUN: %target-swift-ide-test -print-comments -source-filename %s | FileCheck %s
+
+protocol ParentProtocol1 {
+  /// ParentProtocol1.onlyParent1()
+  func onlyParent1()
+  // CHECK: Func/ParentProtocol1.onlyParent1 {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>onlyParent1()</Name><USR>s:FP14swift_ide_test15ParentProtocol111onlyParent1FT_T_</USR><Declaration>func onlyParent1()</Declaration><Abstract><Para>ParentProtocol1.onlyParent1()</Para></Abstract></Function>]
+
+  /// ParentProtocol1.commonParentRequirement()
+  func commonParentRequirement()
+  // CHECKL: Func/ParentProtocol1.commonParentRequirement {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonParentRequirement()</Name><USR>s:FP14swift_ide_test15ParentProtocol123commonParentRequirementFT_T_</USR><Declaration>func commonParentRequirement()</Declaration><Abstract><Para>ParentProtocol1.commonParentRequirement()</Para></Abstract></Function>]
+
+  /// ParentProtocol1.commonRequirementWithDocComment()
+  func commonRequirementWithDocComment()
+  // CHECK: Func/ParentProtocol1.commonRequirementWithDocComment {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonRequirementWithDocComment()</Name><USR>s:FP14swift_ide_test15ParentProtocol131commonRequirementWithDocCommentFT_T_</USR><Declaration>func commonRequirementWithDocComment()</Declaration><Abstract><Para>ParentProtocol1.commonRequirementWithDocComment()</Para></Abstract></Function>]
+
+  /// ParentProtocol1.commonRequirementWithoutDocComment()
+  func commonRequirementWithoutDocComment()
+  // CHECK: Func/ParentProtocol1.commonRequirementWithoutDocComment {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonRequirementWithoutDocComment()</Name><USR>s:FP14swift_ide_test15ParentProtocol134commonRequirementWithoutDocCommentFT_T_</USR><Declaration>func commonRequirementWithoutDocComment()</Declaration><Abstract><Para>ParentProtocol1.commonRequirementWithoutDocComment()</Para></Abstract></Function>]
+}
+
+protocol ParentProtocol2 {
+  /// ParentProtocol2.onlyParent2()
+  func onlyParent2()
+  // CHECK: Func/ParentProtocol2.onlyParent2 {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>onlyParent2()</Name><USR>s:FP14swift_ide_test15ParentProtocol211onlyParent2FT_T_</USR><Declaration>func onlyParent2()</Declaration><Abstract><Para>ParentProtocol2.onlyParent2()</Para></Abstract></Function>]
+
+  /// ParentProtocol2.commonParentRequirement()
+  func commonParentRequirement()
+  // CHECK: Func/ParentProtocol2.commonParentRequirement {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonParentRequirement()</Name><USR>s:FP14swift_ide_test15ParentProtocol223commonParentRequirementFT_T_</USR><Declaration>func commonParentRequirement()</Declaration><Abstract><Para>ParentProtocol2.commonParentRequirement()</Para></Abstract></Function>]
+
+  /// ParentProtocol2.commonRequirementWithDocComment()
+  func commonRequirementWithDocComment()
+  // CHECK: Func/ParentProtocol2.commonRequirementWithDocComment {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonRequirementWithDocComment()</Name><USR>s:FP14swift_ide_test15ParentProtocol231commonRequirementWithDocCommentFT_T_</USR><Declaration>func commonRequirementWithDocComment()</Declaration><Abstract><Para>ParentProtocol2.commonRequirementWithDocComment()</Para></Abstract></Function>]
+
+  /// ParentProtocol2.commonRequirementWithoutDocComment()
+  func commonRequirementWithoutDocComment()
+  // CHECK: Func/ParentProtocol2.commonRequirementWithoutDocComment {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonRequirementWithoutDocComment()</Name><USR>s:FP14swift_ide_test15ParentProtocol234commonRequirementWithoutDocCommentFT_T_</USR><Declaration>func commonRequirementWithoutDocComment()</Declaration><Abstract><Para>ParentProtocol2.commonRequirementWithoutDocComment()</Para></Abstract></Function>]
+}
+
+protocol ChildProtocol : ParentProtocol1, ParentProtocol2 {
+  /// ChildProtocol.commonRequirementWithDocComment()
+  func commonRequirementWithDocComment()
+  // CHECK: Func/ChildProtocol.commonRequirementWithDocComment {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>commonRequirementWithDocComment()</Name><USR>s:FP14swift_ide_test13ChildProtocol31commonRequirementWithDocCommentFT_T_</USR><Declaration>func commonRequirementWithDocComment()</Declaration><Abstract><Para>ChildProtocol.commonRequirementWithDocComment()</Para></Abstract></Function>]
+
+  // This should show nothing because there are two inherited requirements.
+  func commonRequirementWithoutDocComment()
+  // CHECK: Func/ChildProtocol.commonRequirementWithoutDocComment {{.*}} DocCommentAsXML=none
+}
+
+// Test that ChildProtocol's default implementation for requirements
+// come from the right place.
+extension ChildProtocol {
+  // Should come from ParentProtocol1.
+  func onlyParent1() {}
+  // CHECK: Func/onlyParent1 {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>onlyParent1()</Name><USR>s:FP14swift_ide_test15ParentProtocol111onlyParent1FT_T_</USR><Declaration>func onlyParent1()</Declaration><Abstract><Para>ParentProtocol1.onlyParent1()</Para></Abstract></Function>]
+
+  // Should come from ParentProtocol2.
+  func onlyParent2() {}
+  // CHECK: Func/onlyParent2 {{.*}} DocCommentAsXML=[<Function file="{{.*}}" line="{{.*}}" column="{{.*}}"><Name>onlyParent2()</Name><USR>s:FP14swift_ide_test15ParentProtocol211onlyParent2FT_T_</USR><Declaration>func onlyParent2()</Declaration><Abstract><Para>ParentProtocol2.onlyParent2()</Para></Abstract></Function>]
+
+  // Should show nothing because the requirement is in both parents.
+  func commonParentRequirement() {}
+  // CHECK: Func/commonParentRequirement {{.*}} DocCommentAsXML=none
+
+  // Should show nothing because the requirement is in both parents.
+  func commonRequirementWithDocComment() {}
+  // CHECK: Func/commonRequirementWithDocComment {{.*}} DocCommentAsXML=none
+
+  // Should show nothing because there are multiple requirements.
+  func commonRequirementWithoutDocComment() {}
+  // CHECK: Func/commonRequirementWithoutDocComment {{.*}} DocCommentAsXML=none
+}
+