Bad error message: varying arguments

A function definition like

f :: Maybe () -> Char
f Nothing = 'a'
f Just () = 'b'

yields the error message

Varying number of arguments for function `f'

under 6.4.1 (pointing to the line with Nothing as containing the error). The following error message would be easier to understand for beginners (pointing to the line with Just):

The type signature for f specifies that the function should take one argument, but you have given it two arguments.

Trac metadata

Trac field	Value
Version	6.4.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown