diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 9e635cafd13a3..aafdc1afc28b9 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -5032,8 +5032,6 @@ export interface TypeCheckerHost extends ModuleSpecifierResolutionHost {
 
 export interface TypeChecker {
     
-    /** @internal */
-    fillMissingTypeArguments(typeArguments: readonly Type[], typeParameters: readonly TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean): Type[];
     getTypeOfSymbolAtLocation(symbol: Symbol, node: Node): Type;
     getTypeOfSymbol(symbol: Symbol): Type;
     getDeclaredTypeOfSymbol(symbol: Symbol): Type;
@@ -5397,6 +5395,7 @@ export interface TypeChecker {
     /** @internal */ isTypeParameterPossiblyReferenced(tp: TypeParameter, node: Node): boolean;
     /** @internal */ typeHasCallOrConstructSignatures(type: Type): boolean;
     /** @internal */ getSymbolFlags(symbol: Symbol): SymbolFlags;
+    /** @internal */ fillMissingTypeArguments(typeArguments: readonly Type[], typeParameters: readonly TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean): Type[];
 }
 
 /** @internal */
diff --git a/src/services/codefixes/helpers.ts b/src/services/codefixes/helpers.ts
index f71f66bac3d17..e29ac09fb59dd 100644
--- a/src/services/codefixes/helpers.ts
+++ b/src/services/codefixes/helpers.ts
@@ -619,10 +619,9 @@ export function typeNodeToAutoImportableTypeNode(typeNode: TypeNode, importAdder
     return getSynthesizedDeepClone(typeNode);
 }
 
-function endOfRequiredTypeParameters(checker: TypeChecker, type: GenericType, fullTypeArguments: readonly Type[]) : number {
-    if (fullTypeArguments !== type.typeArguments!) {
-        throw new Error('fullTypeArguments should be set')
-    }
+function endOfRequiredTypeParameters(checker: TypeChecker, type: GenericType): number {
+    Debug.assert(type.typeArguments);
+    const fullTypeArguments = type.typeArguments;
     const target = type.target;
     next_cutoff: for (let cutoff = 0; cutoff < fullTypeArguments.length; cutoff++) {
         const typeArguments = fullTypeArguments.slice(0, cutoff);
@@ -635,7 +634,7 @@ function endOfRequiredTypeParameters(checker: TypeChecker, type: GenericType, fu
     }
     // If we make it all the way here, all the type arguments are required.
     return fullTypeArguments.length;
-    }
+}
 
 export function typeToMinimizedReferenceType(checker: TypeChecker, type: Type, contextNode: Node | undefined, flags?: NodeBuilderFlags, internalFlags?: InternalNodeBuilderFlags, tracker?: SymbolTracker): TypeNode | undefined {
     const typeNode = checker.typeToTypeNode(type, contextNode, flags, internalFlags, tracker);
@@ -645,9 +644,9 @@ export function typeToMinimizedReferenceType(checker: TypeChecker, type: Type, c
     if (isTypeReferenceNode(typeNode)) {
         const genericType = type as GenericType;
         if (genericType.typeArguments) {
-            const cutoff = endOfRequiredTypeParameters(checker, genericType, genericType.typeArguments);
+            const cutoff = endOfRequiredTypeParameters(checker, genericType);
             if (cutoff !== undefined && typeNode.typeArguments) {
-                // Looks like the wrong way to do this. What APIs should I use here?
+                // Cast to any to mutate the newly created TypeNode
                 (typeNode as any).typeArguments = typeNode.typeArguments.slice(0, cutoff);
             }
         }