[code-completion] Avoid name copy for non dynamic member types

Per review feedback. Also add some test cases that should fail dynamic
member lookup.

Author: benlangmuir

lib/Sema/LookupVisibleDecls.cpp

@@ -628,9 +628,7 @@ static void lookupVisibleDynamicMemberLookupDecls(
     LookupState LS, DeclVisibilityKind reason, LazyResolver *typeResolver,
     GenericSignatureBuilder *GSB, VisitedSet &visited) {
 
-  if (!hasDynamicMemberLookupAttribute(baseType))
-    return;
-
+  assert(hasDynamicMemberLookupAttribute(baseType));
   auto &ctx = dc->getASTContext();
 
   // Lookup the `subscript(dynamicMember:)` methods in this type.
@@ -652,9 +650,12 @@ static void lookupVisibleDynamicMemberLookupDecls(
 
     auto subs =
         baseType->getMemberSubstitutionMap(dc->getParentModule(), subscript);
-    if (auto memberType = rootType->subst(subs))
-      lookupVisibleMemberDeclsImpl(memberType, consumer, dc, LS, reason,
-                                   typeResolver, GSB, visited);
+    auto memberType = rootType->subst(subs);
+    if (!memberType || !memberType->mayHaveMembers())
+      continue;
+
+    lookupVisibleMemberDeclsImpl(memberType, consumer, dc, LS, reason,
+                                 typeResolver, GSB, visited);
   }
 }
 
@@ -888,13 +889,15 @@ static void lookupVisibleMemberDecls(
   lookupVisibleMemberDeclsImpl(BaseTy, overrideConsumer, CurrDC, LS, Reason,
                                TypeResolver, GSB, Visited);
 
-  llvm::DenseSet<DeclBaseName> knownMembers;
-  for (auto &kv : overrideConsumer.FoundDecls) {
-    knownMembers.insert(kv.first);
+  if (hasDynamicMemberLookupAttribute(BaseTy)) {
+    llvm::DenseSet<DeclBaseName> knownMembers;
+    for (auto &kv : overrideConsumer.FoundDecls) {
+      knownMembers.insert(kv.first);
+    }
+    ShadowedKeyPathMembers dynamicConsumer(overrideConsumer, knownMembers);
+    lookupVisibleDynamicMemberLookupDecls(BaseTy, dynamicConsumer, CurrDC, LS,
+                                          Reason, TypeResolver, GSB, Visited);
   }
-  ShadowedKeyPathMembers dynamicConsumer(overrideConsumer, knownMembers);
-  lookupVisibleDynamicMemberLookupDecls(BaseTy, dynamicConsumer, CurrDC, LS,
-                                        Reason, TypeResolver, GSB, Visited);
 
   // Report the declarations we found to the real consumer.
   for (const auto &DeclAndReason : overrideConsumer.DeclsToReport)

test/IDE/complete_keypath_member_lookup.swift

@@ -12,6 +12,10 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=testProtocolConform1 | %FileCheck %s -check-prefix=testProtocolConform1
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=OnSelf1 | %FileCheck %s -check-prefix=OnSelf1
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=testSelfExtension1 | %FileCheck %s -check-prefix=testSelfExtension1
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=testInvalid1 | %FileCheck %s -check-prefix=testInvalid1
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=testInvalid2 | %FileCheck %s -check-prefix=testInvalid2
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=testInvalid3 | %FileCheck %s -check-prefix=testInvalid3
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=testInvalid4 | %FileCheck %s -check-prefix=testInvalid4
 
 struct Point {
   var x: Int
@@ -219,3 +223,48 @@ extension Lens where T: HalfRect {
 // testSelfExtension1-NOT: bottomRight
 // testSelfExtension1: Decl[InstanceVar]/CurrNominal:      topLeft[#Point#];
 // testSelfExtension1-NOT: bottomRight
+
+struct Invalid1 {
+  subscript<U>(dynamicMember member: KeyPath<Rectangle, U>) -> U {
+    return Point(x: 0, y: 1)[keyPath: member]
+  }
+}
+func testInvalid1(r: Invalid1) {
+  r.#^testInvalid1^#
+}
+// testInvalid1-NOT: topLeft
+
+@dynamicMemberLookup
+struct Invalid2 {
+  subscript<U>(dynamicMember: KeyPath<Rectangle, U>) -> U {
+    return Point(x: 0, y: 1)[keyPath: dynamicMember]
+  }
+}
+func testInvalid2(r: Invalid2) {
+  r.#^testInvalid2^#
+}
+// testInvalid2-NOT: topLeft
+
+@dynamicMemberLookup
+struct Invalid3 {
+  subscript<U>(dynamicMember member: Rectangle) -> U {
+    return Point(x: 0, y: 1)[keyPath: member]
+  }
+}
+func testInvalid3(r: Invalid3) {
+  r.#^testInvalid3^#
+}
+// testInvalid3-NOT: topLeft
+
+struct NotKeyPath<T, U> {}
+
+@dynamicMemberLookup
+struct Invalid4 {
+  subscript<U>(dynamicMember member: NotKeyPath<Rectangle, U>) -> U {
+    return Point(x: 0, y: 1)[keyPath: member]
+  }
+}
+func testInvalid4(r: Invalid4) {
+  r.#^testInvalid4^#
+}
+// testInvalid4-NOT: topLeft