for-benny.ts

class FunWithFunctionalTS {

queryEditorState: Readonly<QueryEditorState>;

  static updateEditorState(
    editorState: Readonly<QueryEditorState>,
    sliceToUpdate: Partial<Readonly<QueryEditorState>>
  ): Readonly<QueryEditorState> {
    return { ...editorState, ...sliceToUpdate };
  }
  
  updateEditorOnParseResult(result: Partial<ParseTextResult>): Partial<ParseTextResult> {
    this.queryEditorState = FunWithFunctionalTS.updateEditorState(this.queryEditorState, {
      valid: result.isValid,
      textTokens: result.tokenList
    });
    return result;
  }
  
  doSomething() {
  // g after f LOL
  const result = this.updateEditorOnParseResult(this.parseEditorText(this.queryEditorState.text));
  console.log(result);
  }
  
 }

Actually it will be better if the updateEditorOnParseResult will be void - in this example I just wanted a one line composition in practice I'll split it..