AST: Remove DependentMemberType::substRootParam()

Author: slavapestov

include/swift/AST/Types.h

@@ -7170,11 +7170,6 @@ class DependentMemberType : public TypeBase {
   Type substBaseType(Type base, LookupConformanceFn lookupConformance,
                      SubstOptions options);
 
-  /// Substitute the root generic type, looking up the chain of associated types.
-  /// Returns null if the member could not be found in the new root.
-  Type substRootParam(Type newRoot, LookupConformanceFn lookupConformance,
-                      SubstOptions options);
-
   // Implement isa/cast/dyncast/etc.
   static bool classof(const TypeBase *T) {
     return T->getKind() == TypeKind::DependentMember;

lib/AST/TypeSubstitution.cpp

@@ -282,20 +282,6 @@ Type DependentMemberType::substBaseType(Type substBase,
                               /*level=*/0);
 }
 
-Type DependentMemberType::substRootParam(Type newRoot,
-                                         LookupConformanceFn lookupConformance,
-                                         SubstOptions options) {
-  auto base = getBase();
-  if (base->is<GenericTypeParamType>()) {
-    return substBaseType(newRoot, lookupConformance, options);
-  }
-  if (auto depMem = base->getAs<DependentMemberType>()) {
-    return substBaseType(depMem->substRootParam(newRoot, lookupConformance, options),
-                         lookupConformance, options);
-  }
-  return Type();
-}
-
 static Type substGenericFunctionType(GenericFunctionType *genericFnType,
                                      InFlightSubstitution &IFS) {
   // Substitute into the function type (without generic signature).