Fix #17509: Continue instead of return with unfinished generics (#22563)

Close #17509

Current knowledge:
- delaying cache fixes the issue
- changing return of `if inst.len < key.len:` in `searchInstTypes` to
`continue` fixes the issue. With return the broken types are also cached
over and over

Related issues are completely unaffected as of now, so there must be
something deeper.

I am also still trying to find the true cause, so feel free to ignore
for now

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Co-authored-by: SirOlaf <>

compiler/semtypinst.nim

@@ -45,7 +45,8 @@ proc searchInstTypes*(g: ModuleGraph; key: PType): PType =
       # XXX: This happens for prematurely cached
       # types such as Channel[empty]. Why?
       # See the notes for PActor in handleGenericInvocation
-      return
+      # if this is return the same type gets cached more than it needs to
+      continue
     if not sameFlags(inst, key):
       continue