Require PatternSynonyms language extension to *use* pattern synonyms
To keep in the spirit of #2905, especially in light of the immaturity of the pattern synonyms extensions, GHC should require the PatternSynonyms language extension to be turned on when encountering a pattern synonym occurance.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.8.1-rc2 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler (Type checker) |
| Test case | |
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