id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
10	Show types for subexpressions	nomeata	claus	"Hi,

not sure if this is possible, but it would be nice to use _t even on locally bound identifiers. So if I have

{{{
readTheFile filename = readFile filename
}}}

I could hover the filename (either in the pattern or in the body), and it would show ""String"" or ""FileName"".

This could be achieved by temporarily annotating the value with a type signature, e.g.

{{{
data Dummy = Dummy
readTheFile filename = readFile (filename :: Dummy)
}}}

(where Dummy might be replaced by some random string) and then parsing the error message
{{{
tmp.hs:2:33:
    Couldn't match expected type `FilePath'
           against inferred type `Dummy'
    In the first argument of `readFile', namely `(filename :: Dummy)'
    In the expression: readFile (filename :: Dummy)
    In the definition of `readTheFile':
        readTheFile filename = readFile (filename :: Dummy)
}}}
extracing the type from the ""expected type"" information.

Additional bonus if it works for subexpression in visual mode. E.g., I can select a range in the code and _t gives me the type of the range (if putting that range in brackets and adding a type signature is still valid code).

Thanks,
Joachim"	enhancement	new	minor		compiler/ghc.vim