Being instance of Monoid is not checked
It is possible pass not only instances of Monoid to tell function and load the file with GHCi. GHCi shows type f :: (MonadWriter ((a -> b) -> [a] -> [b]) m) => t -> m ()
f _ = tell map
However, if code is
f = tell map
GHCi shows type error(no instance) as expected.
It seems very strange that type correctness depends on number of parameters for function that is not used anywhere.
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |