TS with .js files and JSDoc: type is found, displayed and used - despite "TS2304: Cannot find name XYZ"

[lll000111]

TS 3.4.5, Webstorm 2019.1.1, node v11.14.0, Linux

Project: .ts files in src/, transpiled using Babel to lib/, but files under test/ are .js files

tsconfig.json has allowJs and checkJs set to true in order to check the .js files under test/ — which (CommonJS) require(...) transpiled .js files from lib/ (there also are .d.ts and .d.ts.map files for all files).

Every single TS type declared in src/ has an accompanying JSDoc @typedef (don't know if that is important or if TS does not even use it since there is the original TS type too).

The problem I see is a weird one, because what Typescript says and what it actually does is completely opposite!

In the IDE I see every single type declared in src/ files as read, and on mouseover I get TS2304 Cannot find name "XYZ".:

However, and this is the weird part (1 of 2): It all works!

Showing the type (in WebStorm, CTRL plus mouse-hover over a symbol, shows the correct information. Even on those red types, I get the type name and the file name of where it is declared. Variables show the correct autocompletion suggestions and type information, jumping to the type definition (the TS one) works too.

The other weird part (2 of 2) is that when I follow the suggestions to change e.g.

 * @param {SHA256Hash} hash

to

 * @param {import('../lib/core-types.js').SHA256Hash} hash

the symbols are no longer red — but now nothing works. No more type information or anything. (Tried different import paths, also directly to the src/ files and without extension, for example.)

This is the reason why I file this as a bug. It actually works, so it is not a feature request.

So all it needs is for TS to stop showing the "cannot find name" errors, I don't need a change in behavior, since it does find the names just fine.

PS: I realize this is probably deeper, the plugin does not specifically remove the comments, I think it is the path.remove() command from the underlying AST. That doesn't make it any better or even right though. Others had similar issues in the past.

[sandersn]

Initial question: are the @typedefs in the .ts files with the TS types? Or are they in .js files somewhere? TS doesn't pay attention to jsdoc types in .ts files.

[sandersn]

Second question: What does tsc do? Does it give the error with or without the import types?

Third question: If you have VS or VS Code, how does it behave? VS is better here since it does less, but of course it's not free. Sublime/vi/emacs are also fine since they don't have other language services at work.

[lll000111]

The @typedefs are in .d.ts files. All types are in .ts files. Those are made into .js files - but for every one of those a corresponding .d.ts file is created. The tests are .js and use (require(...)) the .js files. So I could have type annotations in the test files only with JSDoc, but all type definitions are in the source (TS) files.

There are JSDoc types in the TS src files, but only for HTML API documentation creation purposes. Every TS type declaration has a corresponding JSDoc @typedef so that the type ends up documented in the HTML API doc created by actually running the tool jsdoc3. But it's also nice to get a documentation popup for types where that JSDOc text is shown (for the TS type itself, not just for actual JS variables).

By now the tests are .ts too so this no longer is an issue for me personally any more.
I'm afraid I can't answer the last question any more for this reason.

I use WebStorm.