Don't mangle lifetime dependencies in older runtimes

Author: meg-gupta

include/swift/AST/ASTMangler.h

@@ -91,6 +91,9 @@ class ASTMangler : public Mangler {
   /// a critical role.
   bool AllowTypedThrows = true;
 
+  /// If enabled, lifetime dependencies can be encoded in the mangled name.
+  bool AllowLifetimeDependencies = 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

@@ -3247,7 +3247,7 @@ void ASTMangler::appendFunctionResultType(
     appendType(resultType, sig, forDecl);
   }
 
-  if (lifetimeDependence.has_value()) {
+  if (AllowLifetimeDependencies && lifetimeDependence.has_value()) {
     appendLifetimeDependence(*lifetimeDependence);
   }
 }
@@ -3302,7 +3302,7 @@ void ASTMangler::appendParameterTypeListElement(
   if (flags.isCompileTimeConst())
     appendOperator("Yt");
 
-  if (lifetimeDependence) {
+  if (AllowLifetimeDependencies && lifetimeDependence) {
     appendLifetimeDependence(*lifetimeDependence);
   }
 

lib/IRGen/IRGenMangler.cpp

@@ -163,6 +163,7 @@ IRGenMangler::mangleTypeForReflection(IRGenModule &IGM,
       AllowConcurrencyStandardSubstitutions);
   llvm::SaveAndRestore<bool> savedIsolatedAny(AllowIsolatedAny);
   llvm::SaveAndRestore<bool> savedTypedThrows(AllowTypedThrows);
+  llvm::SaveAndRestore<bool> savedLifetimeDependencies(AllowLifetimeDependencies);
   if (auto runtimeCompatVersion = getSwiftRuntimeCompatibilityVersionForTarget(
           ctx.LangOpts.Target)) {
 
@@ -178,6 +179,7 @@ IRGenMangler::mangleTypeForReflection(IRGenModule &IGM,
     if (*runtimeCompatVersion < llvm::VersionTuple(6, 0)) {
       AllowIsolatedAny = false;
       AllowTypedThrows = false;
+      AllowLifetimeDependencies = false;
     }
   }