[GHC] #10335: Failure to construct superclasses in instance
#10335: Failure to construct superclasses in instance -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Consider {{{ {-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, ConstraintKinds #-} module Foo where class Eq a => C a b type X a = (Eq a, Show a) instance X a => C a [b] }}} HEAD gives {{{ Foo.hs:8:10: Could not deduce (Eq a) arising from the superclasses of an instance declaration from the context: X a bound by the instance declaration at Foo.hs:8:10-23 Possible fix: add (Eq a) to the context of the instance declaration In the instance declaration for ‘C a [b]’ }}} This is fall-out from refactoring the silent-superclass story. Patch coming. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10335 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10335: Failure to construct superclasses in instance
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Reporter: simonpj | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.10.1
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: None/Unknown | Unknown/Multiple
Blocked By: | Test Case:
Related Tickets: | Blocking:
| Differential Revisions:
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Comment (by Simon Peyton Jones
#10335: Failure to construct superclasses in instance -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: merge Priority: normal | Milestone: Component: Compiler | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | typecheck/should_compile/T10335 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by simonpj): * status: new => merge * testcase: => typecheck/should_compile/T10335 Comment: Fixed, although the patch probably won't apply very nicely to 7.10.2, because it meddles with `TcEvidence` which has changed since 7.10. But this patch effectively reverts one of the changes to `TcEvidence` so while it won't apply automatically, it won't be hard either. I'm inclined to think it's worth merging. I can help. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10335#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#10335: Failure to construct superclasses in instance -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.10.2 Component: Compiler | Version: 7.10.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | typecheck/should_compile/T10335 | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Changes (by thoughtpolice): * status: merge => closed * resolution: => fixed * milestone: => 7.10.2 Comment: Merged to `ghc-7.10`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10335#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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