[CodeCompletion] Avoid prioritizing unavailable in LookupVisibleDecls

rdar://problem/67155695

Author: rintaro

lib/Sema/LookupVisibleDecls.cpp

@@ -946,17 +946,22 @@ class OverrideFilteringConsumer : public VisibleDeclConsumer {
                         /*wouldConflictInSwift5*/nullptr,
                         /*skipProtocolExtensionCheck*/true)) {
           FoundConflicting = true;
-          // Prefer derived requirements over their witnesses.
-          if (Reason ==
-                DeclVisibilityKind::MemberOfProtocolDerivedByCurrentNominal ||
-              VD->getFormalAccess() > OtherVD->getFormalAccess() ||
-              //Prefer available one.
-              (!AvailableAttr::isUnavailable(VD) &&
-               AvailableAttr::isUnavailable(OtherVD))) {
-            FilteredResults.remove(
-                FoundDeclTy(OtherVD, DeclVisibilityKind::LocalVariable, {}));
-            FilteredResults.insert(DeclAndReason);
-            *I = VD;
+
+          if (!AvailableAttr::isUnavailable(VD)) {
+            bool preferVD = (
+                // Prefer derived requirements over their witnesses.
+                Reason == DeclVisibilityKind::
+                              MemberOfProtocolDerivedByCurrentNominal ||
+                // Prefer available one.
+                AvailableAttr::isUnavailable(OtherVD) ||
+                // Prefer more accessible one.
+                VD->getFormalAccess() > OtherVD->getFormalAccess());
+            if (preferVD) {
+              FilteredResults.remove(
+                  FoundDeclTy(OtherVD, DeclVisibilityKind::LocalVariable, {}));
+              FilteredResults.insert(DeclAndReason);
+              *I = VD;
+            }
           }
         }
       }

test/IDE/complete_rdar67155695.swift

@@ -0,0 +1,111 @@
+// RUN: %swift-ide-test -code-completion -source-filename %s -code-completion-token=PUBLIC | %FileCheck %s --check-prefix=PUBLIC
+// RUN: %swift-ide-test -code-completion -source-filename %s -code-completion-token=INTERNAL | %FileCheck %s --check-prefix=INTERNAL
+// RUN: %swift-ide-test -code-completion -source-filename %s -code-completion-token=PRIVATE | %FileCheck %s --check-prefix=PRIVATE
+
+public protocol PubP {}
+
+public extension PubP {
+    func availableP_availableC() {}
+
+    func availableP_unavailableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_availableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_unavailableC() {}
+}
+
+struct TestForPubP: PubP {
+    func availableP_availableC() {}
+
+    @available(*, unavailable)
+    func availableP_unavailableC() {}
+
+    func unavailableP_availableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_unavailableC() {}
+}
+
+func test(val: TestForPubP) {
+    val.#^PUBLIC^#
+// PUBLIC: Begin completions, 4 items
+// PUBLIC-DAG: Keyword[self]/CurrNominal:          self[#TestForPubP#];
+// PUBLIC-DAG: Decl[InstanceMethod]/CurrNominal:   unavailableP_availableC()[#Void#];
+// PUBLIC-DAG: Decl[InstanceMethod]/Super:         availableP_availableC()[#Void#];
+// PUBLIC-DAG: Decl[InstanceMethod]/Super:         availableP_unavailableC()[#Void#];
+// PUBLIC: End completions
+}
+
+protocol InternalP {}
+
+extension InternalP {
+    func availableP_availableC() {}
+
+    func availableP_unavailableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_availableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_unavailableC() {}
+}
+
+struct TestForInternalP: InternalP {
+    func availableP_availableC() {}
+
+    @available(*, unavailable)
+    func availableP_unavailableC() {}
+
+    func unavailableP_availableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_unavailableC() {}
+}
+
+func test(val: TestForInternalP) {
+    val.#^INTERNAL^#
+// INTERNAL: Begin completions, 4 items
+// INTERNAL-DAG: Keyword[self]/CurrNominal:          self[#TestForInternalP#];
+// INTERNAL-DAG: Decl[InstanceMethod]/CurrNominal:   availableP_availableC()[#Void#];
+// INTERNAL-DAG: Decl[InstanceMethod]/CurrNominal:   unavailableP_availableC()[#Void#];
+// INTERNAL-DAG: Decl[InstanceMethod]/Super:         availableP_unavailableC()[#Void#];
+// INTERNAL: End completions
+}
+
+private protocol PrivP {}
+
+private extension PrivP {
+    func availableP_availableC() {}
+
+    func availableP_unavailableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_availableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_unavailableC() {}
+}
+
+struct TestForPrivP: PrivP {
+    func availableP_availableC() {}
+
+    @available(*, unavailable)
+    func availableP_unavailableC() {}
+
+    func unavailableP_availableC() {}
+
+    @available(*, unavailable)
+    func unavailableP_unavailableC() {}
+}
+
+func test(val: TestForPrivP) {
+    val.#^PRIVATE^#
+// PRIVATE: Begin completions, 4 items
+// PRIVATE-DAG: Keyword[self]/CurrNominal:          self[#TestForPrivP#];
+// PRIVATE-DAG: Decl[InstanceMethod]/CurrNominal:   availableP_availableC()[#Void#];
+// PRIVATE-DAG: Decl[InstanceMethod]/CurrNominal:   unavailableP_availableC()[#Void#];
+// PRIVATE-DAG: Decl[InstanceMethod]/Super:         availableP_unavailableC()[#Void#];
+// PRIVATE-DAG: End completions
+}