id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
3788	"Improved message for GHC ""No instance for"" Errors"	rhapsodyv		"Hi,

I would like to propose a modification in the ghc message for ""no
instance for"" errors.
In the message, the ghc tells that there's no instance for the type
you are using and it give you a hint that you can fix it adding a new
instance for your type. But it don't tell me any instance alternative
that already exists. So, if I don't know the correct type, I need to
look at the documentation.

At least for me, I get this message when I'm using the function in the
wrong way or when I forget to specify the some function signature.
It's quite rare the I want to add a new instance.
Of course that it's not a problem to look at the documentation, but
improving it can save a significant time and help the beginers to
guess the error and how fix it.

In C++ and Java, when I use g++ or javac and I make a wrong
overloading, the compiler show me some alternatives. I think it help
more than tell me to add a new overload to the function.

It's possible to do it in ghc?"	bug	closed	normal	6.12.2	Compiler	6.10.4	wontfix	errors		Unknown/Multiple	Unknown/Multiple	None/Unknown