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  • #9613

Closed
Open
Opened Sep 19, 2014 by rwbarton@trac-rwbarton

when giving an error "No instance for C (a -> b)", suggest that a function may be underapplied

Suggestion of ibotty here: http://www.reddit.com/r/haskell/comments/2go92u/beginner_error_messages_in_c_vs_haskell/cklm7jk

Prelude> print length

<interactive>:2:1:
    No instance for (Show ([a0] -> Int)) arising from a use of ‘print’
        but there is an instance for (Show Int);
        maybe you omitted an argument to ‘length’ of type [a0]?
    In the expression: print length
    In an equation for ‘it’: it = print length

I guess the trickiest part will be figuring out what function is underapplied.

Trac metadata
Trac field Value
Version 7.8.3
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
BlockedBy
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Blocking
CC
Operating system
Architecture
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Reference: ghc/ghc#9613