TypeScript Version: 3.6.2

Search Terms:

• union type
• partial

Repo

1. git clone https://github.com/Microsoft/typescript-template-language-service-decorator

2. npm install

3. Open src/template-language-service-decorator.ts

4. On line 44, remove the any cast on the line:

       for (const { name, wrapper } of this._wrappers) {
           (intercept[name] as any) = wrapper(languageService[name]!.bind(languageService));
       }

5. Try compiling the project

Expected behavior:
This compiles with TS 3.4

Actual behavior:
Compile fails with TS 3.5+

src/template-language-service-decorator.ts:44:13 - error TS2590: Expression produces a union type that is too complex to represent.

44             intercept[name] = wrapper(languageService[name]!.bind(languageService));
               ~~~~~~~~~~~~~~~

The code likely needs to be rewritten here but I'm opening this issue to make sure the error is expected

Playground Link:

Related Issues: