[Property Wrappers] Intersect the availability of the wrapped/projected value

setter with the availability of the enclosing scope when inferring the
availability of the synthesized setters for an applied property wrapper.

Author: hborla

lib/Sema/TypeCheckStorage.cpp

@@ -1968,6 +1968,17 @@ static AccessorDecl *createSetterPrototype(AbstractStorageDecl *storage,
 
   // Copy availability from the accessor we'll synthesize the setter from.
   SmallVector<Decl *, 2> asAvailableAs;
+
+  auto addEnclosingScopeAvailability = [&]() {
+    Decl *enclosingDecl = storage;
+    // Find the innermost enclosing declaration with an @available annotation.
+    while ((enclosingDecl = enclosingDecl->getDeclContext()->getAsDecl())) {
+      if (enclosingDecl->getAttrs().hasAttribute<AvailableAttr>()) {
+        asAvailableAs.push_back(enclosingDecl);
+        break;
+      }
+    }
+  };
 
   // That could be a property wrapper...
   if (auto var = dyn_cast<VarDecl>(storage)) {
@@ -1978,6 +1989,7 @@ static AccessorDecl *createSetterPrototype(AbstractStorageDecl *storage,
       if (info.valueVar) {
         if (auto setter = info.valueVar->getOpaqueAccessor(AccessorKind::Set)) {
           asAvailableAs.push_back(setter);
+          addEnclosingScopeAvailability();
         }
       }
     } else if (auto wrapperSynthesizedKind
@@ -1995,6 +2007,7 @@ static AccessorDecl *createSetterPrototype(AbstractStorageDecl *storage,
             if (auto setter
                 = info.projectedValueVar->getOpaqueAccessor(AccessorKind::Set)){
               asAvailableAs.push_back(setter);
+              addEnclosingScopeAvailability();
             }
           }
         }

test/Sema/generalized_accessors_availability.swift

@@ -67,3 +67,46 @@ func butt(x: inout Butt) { // expected-note*{{}}
         x.$wrapped_modify_conditionally_available = 0
     }
 }
+
+@available(macOS 11.0, *)
+struct LessAvailable {
+  @SetterConditionallyAvailable
+  var wrapped_setter_more_available: Int
+
+  @ModifyConditionallyAvailable
+  var wrapped_modify_more_available: Int
+
+  var nested: Nested
+
+  struct Nested {
+    @SetterConditionallyAvailable
+    var wrapped_setter_more_available: Int
+
+    @ModifyConditionallyAvailable
+    var wrapped_modify_more_available: Int
+  }
+}
+
+func testInferredAvailability(x: inout LessAvailable) { // expected-error {{'LessAvailable' is only available in macOS 11.0 or newer}} expected-note*{{}}
+  x.wrapped_setter_more_available = 0 // expected-error {{setter for 'wrapped_setter_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+  x.wrapped_modify_more_available = 0 // expected-error {{setter for 'wrapped_modify_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+  x.$wrapped_setter_more_available = 0 // expected-error {{setter for '$wrapped_setter_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+  x.$wrapped_modify_more_available = 0 // expected-error {{setter for '$wrapped_modify_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+
+  x.nested.wrapped_setter_more_available = 0 // expected-error {{setter for 'wrapped_setter_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+  x.nested.wrapped_modify_more_available = 0 // expected-error {{setter for 'wrapped_modify_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+  x.nested.$wrapped_setter_more_available = 0 // expected-error {{setter for '$wrapped_setter_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+  x.nested.$wrapped_modify_more_available = 0 // expected-error {{setter for '$wrapped_modify_more_available' is only available in macOS 11.0 or newer}} expected-note{{}}
+
+  if #available(macOS 11.0, *) {
+    x.wrapped_setter_more_available = 0
+    x.wrapped_modify_more_available = 0
+    x.$wrapped_setter_more_available = 0
+    x.$wrapped_modify_more_available = 0
+
+    x.nested.wrapped_setter_more_available = 0
+    x.nested.wrapped_modify_more_available = 0
+    x.nested.$wrapped_setter_more_available = 0
+    x.nested.$wrapped_modify_more_available = 0
+  }
+}