Alternative instance for Data.Functor.Compose causes <<loop>>s with some types
many and some are omitted and are filled in by their defaults from Alternative, instead of re-using the definitions provided for f; this manifests as infinite grammars being created in the case of the Earley parsing library, resulting in <<loop>> errors at runtime.
The fix is just to add:
many = Compose . fmap sequenceA . many . getCompose
some = Compose . fmap sequenceA . some . getComposeRelated twitter thread: https://twitter.com/ollfredo/status/1067498140100628480
(It seems like this bug has been around for some time: https://github.com/feuerbach/regex-applicative/issues/19)
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.6.2 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | libraries/base |
| Test case | |
| Differential revisions | |
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| CC | |
| Operating system | |
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