Diagnose deployment constraints on type metadata involving typed throws

Fixes the rest of rdar://121530587.

Author: DougGregor

include/swift/AST/DiagnosticsSema.def

@@ -6735,6 +6735,11 @@ ERROR(availability_isolated_any_only_version_newer, none,
       "%0 %1 or newer",
       (StringRef, llvm::VersionTuple))
 
+ERROR(availability_typed_throws_only_version_newer, none,
+      "runtime support for typed throws function types is only available in "
+      "%0 %1 or newer",
+      (StringRef, llvm::VersionTuple))
+
 ERROR(availability_variadic_type_only_version_newer, none,
       "parameter packs in generic types are only available in %0 %1 or newer",
       (StringRef, llvm::VersionTuple))

lib/Sema/TypeCheckAvailability.cpp

@@ -3023,6 +3023,15 @@ static bool diagnoseIsolatedAnyAvailability(
       ReferenceDC);
 }
 
+static bool diagnoseTypedThrowsAvailability(
+    SourceRange ReferenceRange, const DeclContext *ReferenceDC) {
+  return TypeChecker::checkAvailability(
+      ReferenceRange,
+      ReferenceDC->getASTContext().getTypedThrowsAvailability(),
+      diag::availability_typed_throws_only_version_newer,
+      ReferenceDC);
+}
+
 static bool checkTypeMetadataAvailabilityInternal(CanType type,
                                                   SourceRange refLoc,
                                                   const DeclContext *refDC) {
@@ -3033,6 +3042,8 @@ static bool checkTypeMetadataAvailabilityInternal(CanType type,
       auto isolation = fnType->getIsolation();
       if (isolation.isErased())
         return diagnoseIsolatedAnyAvailability(refLoc, refDC);
+      if (fnType.getThrownError())
+        return diagnoseTypedThrowsAvailability(refLoc, refDC);
     }
     return false;
   });

test/IRGen/typed_throws.swift

@@ -13,11 +13,14 @@ public enum MyBigError: Error {
 }
 
 // CHECK-MANGLE: @"$s12typed_throws1XVAA1PAAWP" = hidden global [2 x ptr] [ptr @"$s12typed_throws1XVAA1PAAMc", ptr getelementptr inbounds (i8, ptr @"symbolic ySi_____YKc 12typed_throws10MyBigErrorO", {{i32|i64}} 1)]
+@available(SwiftStdlib 6.0, *)
 struct X: P {
   typealias A = (Int) throws(MyBigError) -> Void
 }
 
 func requiresP<T: P>(_: T.Type) { }
+
+@available(SwiftStdlib 6.0, *)
 func createsP() {
   requiresP(X.self)
 }
@@ -27,6 +30,7 @@ func createsP() {
 
 
 // CHECK-LABEL: define {{.*}}hidden swiftcc ptr @"$s12typed_throws13buildMetatypeypXpyF"()
+@available(SwiftStdlib 6.0, *)
 func buildMetatype() -> Any.Type {
   typealias Fn = (Int) throws(MyBigError) -> Void
 

test/Parse/typed_throws.swift

@@ -20,6 +20,7 @@ func testClosures() {
   let _ = { (x: Int, y: Int) throws(MyError) -> Int in x + y }
 }
 
+@available(SwiftStdlib 6.0, *)
 func testTypes() {
   let _ = [(Int, Int) throws(MyError) -> Int]()
 }

test/decl/func/typed_throws_availability.swift

@@ -0,0 +1,22 @@
+// RUN: %target-typecheck-verify-swift -swift-version 5 -module-name test
+
+// REQUIRES: OS=macosx
+
+// RUN: %target-typecheck-verify-swift -target %target-cpu-apple-macos14.4
+
+enum MyError: Error {
+  case fail
+}
+
+func bad() -> Any.Type {
+  // expected-note@-1{{add @available attribute to enclosing global function}}
+  typealias Fn = () throws(MyError) -> ()
+  // expected-error@+2{{runtime support for typed throws function types is only available in macOS 15.0.0 or newer}}
+  // expected-note@+1{{add 'if #available' version check}}
+  return Fn.self
+}
+
+func good() -> Any.Type {
+  typealias Fn = () throws(any Error) -> ()
+  return Fn.self
+}