result code = -1
standard error = {
tests/diagnostics/extension-visibility.slang(17): error 39999: could not specialize generic for arguments of type (MyThing)
    return helper(thing);
                 ^
tests/diagnostics/extension-visibility-a.slang(14): note: see declaration of public func helper<T>(T) -> int
public int helper<T : IThing>(T thing)
           ^~~~~~
}
standard output = {
}