Merge pull request #58547 from apple/revert-58466-rdar-92364955

Revert "[ConstraintSystem] Extend availability check to cover unavailable ext…"

Author: xedin

lib/Sema/ConstraintSystem.cpp

@@ -6266,7 +6266,7 @@ void ConstraintSystem::diagnoseFailureFor(SolutionApplicationTarget target) {
 bool ConstraintSystem::isDeclUnavailable(const Decl *D,
                                          ConstraintLocator *locator) const {
   // First check whether this declaration is universally unavailable.
-  if (AvailableAttr::isUnavailable(D))
+  if (D->getAttrs().isUnavailable(getASTContext()))
     return true;
 
   return TypeChecker::isDeclarationUnavailable(D, DC, [&] {

test/Constraints/availability.swift

@@ -43,25 +43,3 @@ func unavailableFunction(_ x: Int) -> Bool { true } // expected-note {{'unavaila
 func sr13260(_ arr: [Int]) {
   for x in arr where unavailableFunction(x) {} // expected-error {{'unavailableFunction' is unavailable}}
 }
-
-// rdar://92364955 - ambiguity with member declared in unavailable extension
-struct WithUnavailableExt {
-}
-
-@available(*, unavailable)
-extension WithUnavailableExt {
-  static var foo: WithUnavailableExt = WithUnavailableExt()
-}
-
-func test_no_ambiguity_with_unavailable_ext() {
-  struct A {
-    static var foo: A = A()
-  }
-
-  struct Test {
-    init(_: A) {}
-    init(_: WithUnavailableExt) {}
-  }
-
-  _ = Test(.foo) // Ok `A.foo` since `foo` from `WithUnavailableExt` is unavailable
-}