* Get [type] parameter types from @type tag
Previously only the return type was used in cases like this:
```js
/** @type {<T>(param?: T) => T | undefined} */
function g(param) {
return param;
}
```
Now the type parameters from the type tag are used, and the compiler
gets the type of the parameter by using the position in the signature of
the type tag.
Fixes#25618
* Fix split ifs according to PR comments