AST: Use transformTypeParameterPacks() in getOpenedElementSignature()

Author: slavapestov

lib/AST/ASTContext.cpp

@@ -5856,13 +5856,13 @@ ASTContext::getOpenedElementSignature(CanGenericSignature baseGenericSig,
   }
 
   auto eraseParameterPackRec = [&](Type type) -> Type {
-    return type.transformRec([&](Type t) -> llvm::Optional<Type> {
-      if (auto *paramType = t->getAs<GenericTypeParamType>()) {
+    return type.transformTypeParameterPacks([&](SubstitutableType *t) -> llvm::Optional<Type> {
+      if (auto *paramType = dyn_cast<GenericTypeParamType>(t)) {
         if (packElementParams.find(paramType) != packElementParams.end()) {
           return Type(packElementParams[paramType]);
         }
 
-        return t;
+        return Type(t);
       }
       return llvm::None;
     });

validation-test/compiler_crashers_2_fixed/rdar112108253.swift

@@ -0,0 +1,12 @@
+// RUN: %target-swift-frontend -emit-ir %s -disable-availability-checking
+
+public protocol P {
+  associatedtype A
+}
+
+public struct G<each T> {}
+
+public struct S<T: P, each U: P> where repeat T.A == G<repeat each U> {
+    public init(predicate: repeat each U) {}
+}
+