WebGLShader has no properties

TypeScript Version: 3.7.3

Search Terms: array element type checking, error type checking, stops checking function argument types

Code
https://github.com/vjancik/dont-find-me-yet/blob/tsc-issue/src/index.ts#L63-L64

• fails to infer a possible Error type
• and if I set it explicitly (see Playground), fails to enforce it in

https://github.com/vjancik/dont-find-me-yet/blob/tsc-issue/src/index.ts#L146

• createProgram doesn't enforce WebGLShader[] at all on the first argument, or seemingly any of the other arguments as well. I can add any variable in there and the array accepts it (also Playground)

Expected behavior:
Types of fn. arguments on createProgram get enforced correctly.
Optional: Return type on loadShader & createProgram gets inferred correctly as ... | Error

Actual behavior:
The issue doesn't resolve even if I specify all return types on all functions manually.

Playground Link:
Playground link

Related Issues:
No, there are multiple problems and I can't pinpoint the cause in a very specific setup.

src/index.ts の 63-64 行目と 146 行目にある例から始め、リンク先の TypeScript Playground を使って報告された動作を再現します。loadShader と createProgram の推論された Error の戻り値型と引数チェックを比較します。関数の引数が強制され、期待される戻り値型が正しく推論されれば完了です。