* Fix getExpandoSymbol for already-expando symbols
getExpandoSymbol is intended to get the symbol of the expando in a
declaration like
```js
var C = class {
}
```
However, when this occurs in a `module.exports` assignment, alias
resolution already jumps to the exported symbol -- in this case the
expando symbol:
``js
// @filename: first.js
module.exports = class {
}
// @filename: other.js
/* @type {import("./first")} */
var C
```
`getExpandoSymbol` is then called on `class { }` instead of
`module.exports = class { }`.
Previously, `getExpandoSymbol` would incorrectly treat `class { }` the
same as the export assignment and get the expando ... from the expando
itself. This resulted in merging the expando with itself, which causes
bogus errors and could cause other problems.
Now `getExpandoSymbol` checks that the expando "initializer" is
different from the declaration.
* Better check for getExpandoSymbol of expando
Check the declaration directly instead of the initialiser.