Check for uninhabited types in sub-patterns (#12609) #36476
Closed
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This alters the exhaustiveness-checking algorithm for pattern matches to
avoid raising spurious errors about cases not being covered for
uninhabited types.
Specifically, the construct_witness function now returns an Option. If
it sees that DUMMY_WILD_PAT is being used to match on an uninhabited
type it returns None to indicate that there is no witness. We look for
DUMMY_WILD_PAT specifically and not any wildcard pattern so that
wildcard patterns explicitly written by the programmer continue to work
without raising errors about unreachability.