Drop typed throws from the mangling in closure and field reflection metadata

This follows what we just did for `@isolated(any)` function types.

Part of rdar://130858222.

(cherry picked from commit 9604019)

Author: DougGregor

include/swift/AST/ASTMangler.h

@@ -83,6 +83,14 @@ class ASTMangler : public Mangler {
   /// a critical role.
   bool AllowIsolatedAny = true;
 
+  /// If enabled, typed throws can be encoded in the mangled name.
+  /// Suppressing type attributes this way is generally questionable ---
+  /// for example, it does not interact properly with substitutions ---
+  /// and should only be done in situations where it is just going to be
+  /// interpreted as a type and the exact string value does not play
+  /// a critical role.
+  bool AllowTypedThrows = true;
+
   /// If enabled, declarations annotated with @_originallyDefinedIn are mangled
   /// as if they're part of their original module. Disabled for debug mangling,
   /// because lldb wants to find declarations in the modules they're currently

lib/AST/ASTMangler.cpp

@@ -3055,7 +3055,8 @@ void ASTMangler::appendFunctionSignature(AnyFunctionType *fn,
   if (fn->isSendable())
     appendOperator("Yb");
   if (auto thrownError = fn->getEffectiveThrownErrorType()) {
-    if ((*thrownError)->isEqual(fn->getASTContext().getErrorExistentialType())){
+    if ((*thrownError)->isEqual(fn->getASTContext().getErrorExistentialType())
+        || !AllowTypedThrows) {
       appendOperator("K");
     } else {
       appendType(*thrownError, sig);

lib/IRGen/IRGenMangler.cpp

@@ -161,18 +161,23 @@ IRGenMangler::mangleTypeForReflection(IRGenModule &IGM,
   llvm::SaveAndRestore<bool> savedConcurrencyStandardSubstitutions(
       AllowConcurrencyStandardSubstitutions);
   llvm::SaveAndRestore<bool> savedIsolatedAny(AllowIsolatedAny);
+  llvm::SaveAndRestore<bool> savedTypedThrows(AllowTypedThrows);
   if (auto runtimeCompatVersion = getSwiftRuntimeCompatibilityVersionForTarget(
           ctx.LangOpts.Target)) {
+
     if (*runtimeCompatVersion < llvm::VersionTuple(5, 5))
       AllowConcurrencyStandardSubstitutions = false;
 
-    // Suppress @isolated(any) if we're mangling for pre-6.0 runtimes.
+    // Suppress @isolated(any) and typed throws if we're mangling for pre-6.0
+    // runtimes.
     // This is unprincipled but, because of the restrictions in e.g.
     // mangledNameIsUnknownToDeployTarget, should only happen when
     // mangling for certain reflective uses where we have to hope that
     // the exact type identity is generally unimportant.
-    if (*runtimeCompatVersion < llvm::VersionTuple(6, 0))
+    if (*runtimeCompatVersion < llvm::VersionTuple(6, 0)) {
       AllowIsolatedAny = false;
+      AllowTypedThrows = false;
+    }
   }
 
   llvm::SaveAndRestore<bool> savedAllowStandardSubstitutions(

test/IRGen/reflection_metadata_typed_throws.swift

@@ -0,0 +1,32 @@
+// RUN: %target-swift-frontend -emit-ir -target %target-cpu-apple-macos99.99 %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-PRESENT %s
+// RUN: %target-swift-frontend -emit-ir -target %target-cpu-apple-macos14.4 %s | %FileCheck --check-prefix=CHECK --check-prefix=CHECK-SUPPRESSED %s
+
+// REQUIRES: OS=macosx
+// UNSUPPORTED: CPU=arm64e
+
+// Make sure that a dangling-based type description involving typed throws is
+// only used when deploying to runtimes that support it.
+
+// Closure capture metadata:
+
+enum MyError: Error {
+  case fail
+}
+
+// CHECK-LABEL: @"\01l__swift5_reflection_descriptor" = private constant
+// CHECK-PRESENT-SAME: ptr @"symbolic Si_____Ieghdzo_ 32reflection_metadata_typed_throws7MyErrorO"
+// CHECK-SUPPRESSED-SAME: ptr @"symbolic Si_____Ieghdzo_ 32reflection_metadata_typed_throws7MyErrorO"
+// CHECK-LABEL: @metadata = private constant %swift.full_boxmetadata { {{.*}}, ptr @"\01l__swift5_reflection_descriptor" }, align
+func makeClosure(fn: @escaping @Sendable () throws(MyError) -> Int) -> (() throws(MyError)  -> Int) {
+  return { try fn() + 1 }
+}
+
+// Struct field metadata:
+
+public struct MyStruct {
+  let fn: () throws (MyError) -> ()
+}
+
+// CHECK-LABEL: @"$s32reflection_metadata_typed_throws8MyStructVMF" = internal constant
+// CHECK-PRESENT-SAME: ptr @"symbolic yy_____YKc 32reflection_metadata_typed_throws7MyErrorO"
+// CHECK-SUPPRESSED-SAME: ptr @"get_type_metadata yy32reflection_metadata_typed_throws7MyErrorOYKc.1"