Bulat Ziganshin wrote:
Hello Simon,
Wednesday, September 5, 2007, 11:19:28 AM, you wrote:
when you come across a case where GHC produces an
unhelpful message, send it in, along with the program
that produced it,
i have put such tickets about year ago :) basically, it was about
just changing wording: instead of "inferred" write:
Expected type: ...
Actual type: ...
This doesn't help enough. What is an 'expected' type? How is it not
'actual'? I want it to be immediatly clear which type is which.
Say I write
> "x" ++ 'y'
Right now the error is
Couldn't match expected type `[Char]' against inferred type `Char'
In the second argument of `(++)', namely 'y'
What always confuses me is which of these two types is the parameter I
gave, and which is the one expected by the function? Changing 'infered'
to 'actual' is an improvement, but it is not enough.
I would suggest:
(++) expects second argument to be of type '[Char]'
but was given 'y' of type 'Char'
Anothing thing that would be useful is *why* (++) expects a certian
type, say I enter
> "x" ++ [1::Int]
Instead of the above, the following would be more useful:
the function (++) has type: [a] -> [a] -> [a]
the first argument suggests: a = Char
the second argument suggests: a = Int
Twan
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