[GHC] #11515: PartialTypeSignatures suggests a redundant constraint with constraint families
#11515: PartialTypeSignatures suggests a redundant constraint with constraint families -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When I say {{{ {-# LANGUAGE ConstraintKinds, TypeFamilies #-} module Bug where type family ShowSyn a where ShowSyn a = Show a foo :: (ShowSyn a, _) => a -> String foo x = show x }}} I get {{{ Bug.hs:7:20: error: Found constraint wildcard ‘_’ standing for ‘Show a’ To use the inferred type, enable PartialTypeSignatures In the type signature: foo :: (ShowSyn a, _) => a -> String }}} But if I fill in my wildcard with `Show a`, I'll rightly get a redundant constraint. Just a vanilla type synonym works there, but the type family causes trouble. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11515 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11515: PartialTypeSignatures suggests a redundant constraint with constraint families -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => TypedHoles -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11515#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11515: PartialTypeSignatures suggests a redundant constraint with constraint families -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): This appears to be fixed, as of GHC 8.2.2: {{{ $ /opt/ghc/8.2.2/bin/ghci Bug.hs GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:7:20: error: • Found type wildcard ‘_’ standing for ‘()’ To use the inferred type, enable PartialTypeSignatures • In the type signature: foo :: (ShowSyn a, _) => a -> String | 7 | foo :: (ShowSyn a, _) => a -> String | ^ }}} I'll add a regression test. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11515#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11515: PartialTypeSignatures suggests a redundant constraint with constraint families -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
I'll add a regression test.
Thank you! -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11515#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
#11515: PartialTypeSignatures suggests a redundant constraint with constraint
families
-------------------------------------+-------------------------------------
Reporter: goldfire | Owner: (none)
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 8.1
Resolution: | Keywords: TypedHoles
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
-------------------------------------+-------------------------------------
Comment (by Ryan Scott
#11515: PartialTypeSignatures suggests a redundant constraint with constraint families -------------------------------------+------------------------------------- Reporter: goldfire | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: fixed | Keywords: TypedHoles Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: partial- | sigs/should_fail/T11515 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by RyanGlScott): * testcase: => partial-sigs/should_fail/T11515 * status: new => closed * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11515#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler
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