fixes 22479; WIP [backport]

[Araq]

No description provided.

[metagn]

Maybe generic aliases still need to be skipped, similar to what is done here:

Nim/compiler/types.nim

Lines 1955 to 1963 in f98964d

	of tyGenericInvocation, tyGenericInst:
	result = t
	# skip aliases, so this works in the same module but not in another module:
	# type Foo[T] = object
	# type Bar[T] = Foo[T]
	# proc foo[T](x: Bar[T]) = ... # attached to type
	while result.skipModifier.kind in {tyGenericInvocation, tyGenericInst}:
	result = result.skipModifier
	result = nominalRoot(result[0])

skipGenericAlias which sighashes uses has the problem that it only skips 1 alias.

The CI run is gone so I can't say for sure this was the only problem.

[Araq]

Feel free to take over my work, it's a very important bug to fix.