#14751: GHC wrongly warns of incomplete pattern matches when using pattern synonyms. -------------------------------------+------------------------------------- Reporter: vanessamchale | Owner: (none) Type: bug | Status: closed Priority: low | Milestone: Component: Compiler | Version: 8.4.1-alpha1 Resolution: duplicate | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: GHC rejects | (amd64) valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by nomeata): * status: new => closed * resolution: => duplicate Comment: This is expected behaviour: Because pattern synonyms can do arbitrary computations, the compiler does not even attempt to detect when they are complete. You can specify {{{ {-# COMPLETE V #-} }}} to declare that the `V` pattern is complete. Also see #8779. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14751#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler