AST: Types are immutable so there's no reason for TypeBase::findUnresolvedDependentMemberType() to return a 'const'

Author: slavapestov

include/swift/AST/Types.h

@@ -696,7 +696,7 @@ class alignas(1 << TypeAlignInBits) TypeBase
   ///
   /// "Unresolved" dependent member types have no known associated type,
   /// and are only used transiently in the type checker.
-  const DependentMemberType *findUnresolvedDependentMemberType();
+  DependentMemberType *findUnresolvedDependentMemberType();
 
   /// Return the root generic parameter of this type parameter type.
   GenericTypeParamType *getRootGenericParam();

lib/AST/Type.cpp

@@ -4540,10 +4540,10 @@ Type Type::subst(TypeSubstitutionFn substitutions,
   return substType(*this, substitutions, conformances, options);
 }
 
-const DependentMemberType *TypeBase::findUnresolvedDependentMemberType() {
+DependentMemberType *TypeBase::findUnresolvedDependentMemberType() {
   if (!hasTypeParameter()) return nullptr;
 
-  const DependentMemberType *unresolvedDepMemTy = nullptr;
+  DependentMemberType *unresolvedDepMemTy = nullptr;
   Type(this).findIf([&](Type type) -> bool {
     if (auto depMemTy = type->getAs<DependentMemberType>()) {
       if (depMemTy->getAssocType() == nullptr) {