id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
4959	Warning about variables with leading underscore that are used anyway	Lemming		"I use -Wall all the time, which includes -fwarn-unused-binds and -fwarn-unused-matches that warn about variable bindings that are not used. It already spotted lots of mistakes for me. You can suppress the warning by prepending an underscore '_' to a variable name. However, I have recently seen code, where variable names with leading underscores are regularly used, where other programmers might have chosen trailing underscores or primes. I suspect that the programmer was not aware, that he disabled warnings about unused bindings this way. Thus I like to have a warning about underscored variables that are used in the sense of the definition given for -fwarn-unused-binds in http://www.haskell.org/ghc/docs/latest/html/users_guide/options-sanity.html.
We still have to decide whether this warning should be part of -Wall or -fwarn-unused-binds or whether there should be a separate option like -fwarn-used-underscored-binds.
"	feature request	new	low	7.6.2	Compiler (Parser)	7.0.1		warning unused underscore variable	ghc@…	Unknown/Multiple	Unknown/Multiple	None/Unknown