Marked internal createAnonymousType type as allowing undefined Symbols

Author: JoshuaKGoldberg

src/compiler/types.ts

@@ -3506,7 +3506,7 @@ namespace ts {
         /* @internal */ createPromiseType(type: Type): Type;
 
         /* @internal */ isTypeAssignableTo(source: Type, target: Type): boolean;
-        /* @internal */ createAnonymousType(symbol: Symbol, members: SymbolTable, callSignatures: Signature[], constructSignatures: Signature[], stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): Type;
+        /* @internal */ createAnonymousType(symbol: Symbol | undefined, members: SymbolTable, callSignatures: Signature[], constructSignatures: Signature[], stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): Type;
         /* @internal */ createSignature(
             declaration: SignatureDeclaration,
             typeParameters: TypeParameter[] | undefined,

src/services/codefixes/inferFromUsage.ts

@@ -992,7 +992,7 @@ namespace ts.codefix {
             const callSignatures: Signature[] = usage.calls ? [getSignatureFromCalls(usage.calls)] : [];
             const constructSignatures: Signature[] = usage.constructs ? [getSignatureFromCalls(usage.constructs)] : [];
             const stringIndexInfo = usage.stringIndex && checker.createIndexInfo(combineFromUsage(usage.stringIndex), /*isReadonly*/ false);
-            return checker.createAnonymousType(/*symbol*/ undefined!, members, callSignatures, constructSignatures, stringIndexInfo, /*numberIndexInfo*/ undefined); // TODO: GH#18217
+            return checker.createAnonymousType(/*symbol*/ undefined, members, callSignatures, constructSignatures, stringIndexInfo, /*numberIndexInfo*/ undefined);
         }
 
         function inferNamedTypesFromProperties(usage: Usage): Type[] {