AST: Allow obsoletion in Swift version to disambiguate overloads consistently.

It must be possible to disambiguate overloads using the module-wide Swift
language version, even in contexts that are themselves obsolete in the current
Swift language version.

Resolves rdar://158620835.

lib/AST/AvailabilityConstraint.cpp

@@ -155,20 +155,20 @@ static bool canIgnoreConstraintInUnavailableContexts(
     const AvailabilityConstraintFlags flags) {
   auto domain = constraint.getDomain();
 
-  switch (constraint.getReason()) {
-  case AvailabilityConstraint::Reason::UnavailableUnconditionally:
-    if (flags.contains(AvailabilityConstraintFlag::
-                           AllowUniversallyUnavailableInCompatibleContexts))
-      return true;
-
-    // Always reject uses of universally unavailable declarations, regardless
-    // of context, since there are no possible compilation configurations in
-    // which they are available. However, make an exception for types and
-    // conformances, which can sometimes be awkward to avoid references to.
+  // Always reject uses of universally unavailable declarations, regardless
+  // of context, since there are no possible compilation configurations in
+  // which they are available. However, make an exception for types and
+  // conformances, which can sometimes be awkward to avoid references to.
+  if (!flags.contains(AvailabilityConstraintFlag::
+                      AllowUniversallyUnavailableInCompatibleContexts)) {
     if (!isa<TypeDecl>(decl) && !isa<ExtensionDecl>(decl)) {
       if (domain.isUniversal() || domain.isSwiftLanguage())
         return false;
     }
+  }
+
+  switch (constraint.getReason()) {
+  case AvailabilityConstraint::Reason::UnavailableUnconditionally:
     return true;
 
   case AvailabilityConstraint::Reason::Unintroduced:

test/SILGen/availability_overloads.swift

@@ -52,19 +52,34 @@ public class BeforeAndAfter {
 
 
 // Make sure we can generate calls to these overloads, too
-_ = BeforeAndAfter(foo: ())
-_ = try BeforeAndAfter()
-_ = try BeforeAndAfter.foo()
-_ = BeforeAndAfter.computed
-BeforeAndAfter.computed = 10
-_ = try BeforeAndAfter().computed
-try BeforeAndAfter().computed = 10
+public func testLocal() throws {
+  _ = BeforeAndAfter(foo: ())
+  _ = try BeforeAndAfter()
+  _ = try BeforeAndAfter.foo()
+  _ = BeforeAndAfter.computed
+  BeforeAndAfter.computed = 10
+  _ = try BeforeAndAfter().computed
+  try BeforeAndAfter().computed = 10
+}
+
+@available(swift, obsoleted: 4.0)
+public func testLocalObsoleted() throws {
+  _ = BeforeAndAfter(foo: ())
+  _ = try BeforeAndAfter()
+  _ = try BeforeAndAfter.foo()
+  _ = BeforeAndAfter.computed
+  BeforeAndAfter.computed = 10
+  _ = try BeforeAndAfter().computed
+  try BeforeAndAfter().computed = 10
+}
 
 // Same thing but in a different module
-_ = BeforeAndAfterOther(foo: ())
-_ = try BeforeAndAfterOther()
-_ = try BeforeAndAfterOther.foo()
-_ = BeforeAndAfterOther.computed
-BeforeAndAfterOther.computed = 10
-_ = try BeforeAndAfterOther().computed
-try BeforeAndAfterOther().computed = 10
+public func testOtherModule() throws {
+  _ = BeforeAndAfterOther(foo: ())
+  _ = try BeforeAndAfterOther()
+  _ = try BeforeAndAfterOther.foo()
+  _ = BeforeAndAfterOther.computed
+  BeforeAndAfterOther.computed = 10
+  _ = try BeforeAndAfterOther().computed
+  try BeforeAndAfterOther().computed = 10
+}

test/attr/attr_availability_transitive.swift

@@ -59,8 +59,8 @@ func never_available_func(
 ) {
   always()
   never() // expected-error {{'never()' is unavailable}}
-  unavailableInSwift4()
-  availableInFutureSwift()
+  unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+  availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 }
 
 @available(swift, obsoleted: 4)
@@ -72,8 +72,8 @@ func unavailable_in_swift4_func(
 ) {
   always()
   never() // expected-error {{'never()' is unavailable}}
-  unavailableInSwift4()
-  availableInFutureSwift()
+  unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+  availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 }
 
 @available(swift, introduced: 99)
@@ -85,8 +85,8 @@ func introduced_in_future_swift_func(
 ) {
   always()
   never() // expected-error {{'never()' is unavailable}}
-  unavailableInSwift4()
-  availableInFutureSwift()
+  unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+  availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 }
 
 // MARK: Global vars
@@ -112,8 +112,8 @@ var never_var: (
 ) = (
   always(),
   never(), // expected-error {{'never()' is unavailable}}
-  unavailableInSwift4(),
-  availableInFutureSwift(),
+  unavailableInSwift4(), // expected-error {{'unavailableInSwift4()' is unavailable}}
+  availableInFutureSwift(), // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 )
 
 @available(swift, obsoleted: 4)
@@ -125,8 +125,8 @@ var unavailable_in_swift4_var: (
 ) = (
   always(),
   never(), // expected-error {{'never()' is unavailable}}
-  unavailableInSwift4(),
-  availableInFutureSwift(),
+  unavailableInSwift4(), // expected-error {{'unavailableInSwift4()' is unavailable}}
+  availableInFutureSwift(), // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 )
 
 @available(swift, introduced: 99)
@@ -138,8 +138,8 @@ var available_in_future_swift_var: (
 ) = (
   always(),
   never(), // expected-error {{'never()' is unavailable}}
-  unavailableInSwift4(),
-  availableInFutureSwift(),
+  unavailableInSwift4(), // expected-error {{'unavailableInSwift4()' is unavailable}}
+  availableInFutureSwift(), // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 )
 
 
@@ -159,8 +159,8 @@ struct AlwaysAvailableContainer {
 struct NeverAvailableContainer { // expected-note 3 {{'NeverAvailableContainer' has been explicitly marked unavailable here}}
   let always_var: AlwaysAvailable = always()
   let never_var: NeverAvailable = never() // expected-error {{'never()' is unavailable}}
-  let unavailable_in_swift4_var: UnavailableInSwift4 = unavailableInSwift4()
-  let available_in_future_swift_var: AvailableInFutureSwift = availableInFutureSwift()
+  let unavailable_in_swift4_var: UnavailableInSwift4 = unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+  let available_in_future_swift_var: AvailableInFutureSwift = availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 }
 
 @available(swift, obsoleted: 4)
@@ -168,8 +168,8 @@ struct UnavailableInSwift4Container { // expected-note {{'UnavailableInSwift4Con
   let always_var: AlwaysAvailable = always()
   let never_var: NeverAvailable = never() // expected-error {{'never()' is unavailable}}
   // expected-error@-1 {{'NeverAvailable' is unavailable}}
-  let unavailable_in_swift4_var: UnavailableInSwift4 = unavailableInSwift4()
-  let available_in_future_swift_var: AvailableInFutureSwift = availableInFutureSwift()
+  let unavailable_in_swift4_var: UnavailableInSwift4 = unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+  let available_in_future_swift_var: AvailableInFutureSwift = availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 }
 
 @available(swift, introduced: 99)
@@ -177,8 +177,8 @@ struct AvailableInFutureSwiftContainer { // expected-note {{'AvailableInFutureSw
   let always_var: AlwaysAvailable = always()
   let never_var: NeverAvailable = never() // expected-error {{'never()' is unavailable}}
   // expected-error@-1 {{'NeverAvailable' is unavailable}}
-  let unavailable_in_swift4_var: UnavailableInSwift4 = unavailableInSwift4()
-  let available_in_future_swift_var: AvailableInFutureSwift = availableInFutureSwift()
+  let unavailable_in_swift4_var: UnavailableInSwift4 = unavailableInSwift4()  // expected-error {{'unavailableInSwift4()' is unavailable}}
+  let available_in_future_swift_var: AvailableInFutureSwift = availableInFutureSwift()  // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
 }
 
 // MARK: Extensions
@@ -229,8 +229,8 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    unavailableInSwift4()
-    availableInFutureSwift()
+    unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+    availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
   }
 
   @available(*, unavailable)
@@ -242,8 +242,8 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    unavailableInSwift4()
-    availableInFutureSwift()
+    unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+    availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
   }
 
   @available(swift, obsoleted: 4)
@@ -255,8 +255,8 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    unavailableInSwift4()
-    availableInFutureSwift()
+    unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+    availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
   }
 
   @available(swift, introduced: 99)
@@ -268,8 +268,8 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    unavailableInSwift4()
-    availableInFutureSwift()
+    unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+    availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
   }
 }
 
@@ -286,8 +286,8 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    unavailableInSwift4()
-    availableInFutureSwift()
+    unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+    availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
   }
 }
 
@@ -304,8 +304,8 @@ extension ExtendMe {
   ) {
     always()
     never() // expected-error {{'never()' is unavailable}}
-    unavailableInSwift4()
-    availableInFutureSwift()
+    unavailableInSwift4() // expected-error {{'unavailableInSwift4()' is unavailable}}
+    availableInFutureSwift() // expected-error {{'availableInFutureSwift()' is unavailable in Swift}}
   }
 }