#15703: Significant compilation time blowup when refactoring singletons-heavy code -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Those are staggeringly large coercions decorating relatively tiny types. I wonder: could any of them be very large representations of `Refl`? I note that `OptCoercion` doesn't use `isReflexiveCo` (which tests for equality of the two types) because doing so at every node would be expensive. But you could try testing for `isReflexiveCo`, and spit out the smallest coercion which says `True` to `isReflexiveCo` but is not actually `Refl`. You'd want to make this test for every sub-tree in the coercion. That's a guess. But it's very hard to imagine that you ''really'' need such large proofs. The trick is to find where the redundancy is. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15703#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler