Sema: Always query abstract syntax decls for availability attributes.

Author: tshortli

lib/Sema/TypeCheckAvailability.cpp

@@ -348,8 +348,7 @@ static const AvailableAttr *getActiveAvailableAttribute(const Decl *D,
 
 /// Returns true if there is any availability attribute on the declaration
 /// that is active on the target platform.
-static bool hasActiveAvailableAttribute(Decl *D,
-                                           ASTContext &AC) {
+static bool hasActiveAvailableAttribute(const Decl *D, ASTContext &AC) {
   return getActiveAvailableAttribute(D, AC);
 }
 
@@ -718,9 +717,13 @@ class TypeRefinementContextBuilder : private ASTWalker {
     return nullptr;
   }
 
-  const AvailabilityContext getEffectiveAvailabilityForDeclSignature(Decl *D) {
+  const AvailabilityContext
+  getEffectiveAvailabilityForDeclSignature(const Decl *D) {
     auto EffectiveIntroduction = AvailabilityRange::alwaysAvailable();
 
+    // Availability attributes are found abstract syntax decls.
+    D = abstractSyntaxDeclForAvailableAttribute(D);
+
     // As a special case, extension decls are treated as effectively as
     // available as the nominal type they extend, up to the deployment target.
     // This rule is a convenience for library authors who have written
@@ -754,7 +757,7 @@ class TypeRefinementContextBuilder : private ASTWalker {
   /// are not constrained since they appear in the interface of the module and
   /// may be consumed by clients with lower deployment targets, but there are
   /// some exceptions.
-  bool shouldConstrainSignatureToDeploymentTarget(Decl *D) {
+  bool shouldConstrainSignatureToDeploymentTarget(const Decl *D) {
     if (isCurrentTRCContainedByDeploymentTarget())
       return false;
 

test/Sema/availability_refinement_contexts.swift

@@ -319,6 +319,16 @@ func unavailableOnMacOS() {
   let x = 1
 }
 
+// CHECK-NEXT: {{^}}  (decl_implicit version=50 decl=extension.SomeEnum
+// CHECK-NEXT: {{^}}    (decl version=51 decl=extension.SomeEnum
+// CHECK-NEXT: {{^}}      (decl_implicit version=51 decl=unavailableOnMacOS
+// CHECK-NEXT: {{^}}        (decl_implicit version=51 unavailable=macOS decl=unavailableOnMacOS
+@available(OSX 51, *)
+extension SomeEnum {
+  @available(macOS, unavailable)
+  var unavailableOnMacOS: Int { 1 }
+}
+
 // CHECK-NEXT: {{^}}  (decl_implicit version=50 decl=extension.SomeEnum
 // CHECK-NEXT: {{^}}    (decl_implicit version=50 unavailable=macOS decl=extension.SomeEnum
 // CHECK-NEXT: {{^}}      (decl_implicit version=50 unavailable=macOS decl=availableMacOS_52