When I delete pkl-core/src/test/files/LanguageSnippetTests/output and
run "gw test", most output files are regenerated, but 46 of them aren't.
I assume these are stale files that should be deleted.
The body of a typealias gets inlined into wherever the typealias
is used. This fixes a bug where the references in the typealias body can
resolve to the wrong value.
Daniel Chao