Error message for accidentally using -> instead of =>
Consider the following typo:
sort :: Ord s -> [s] -> [s]
sort xs = Data.List.sort xs
GHC's error message in 7.10 is
Expected a type, but ‘Ord s’ has kind ‘GHC.Prim.Constraint’
In the type signature for ‘Main.sort’:
Main.sort :: Ord s -> [s] -> [s]
I would suggest that mentioning kinds and GHC.Prim.Constraint is a bit unfriendly in a vanilla session (with ConstraintKinds etc switched off).
For comparison, the 6.12 error message was
Class `Ord' used as a type
In the type signature for `sort': sort :: Ord a -> [a] -> [a]
Trac metadata
Trac field | Value |
---|---|
Version | 7.10.2 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
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