id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
2452	Add a flag to disable the implicit qualified import of every available module in interactive mode	jcpetruzza	simonmar	"In interactive mode every available module is implicitly imported qualified. While this is very convenient when working with GHCi, it can be a little annoying in other contexts.

For instance, in a lambdabot-like application, one would like to rely on the type of a given expression to decide if it is side-effect free and, thus, safe to execute. However, because every module in the `base` package is imported qualified one has to do a manual check to filter out cases like:

{{{
ghc -e 'System.IO.Unsafe.unsafePerformIO (evilStuff >> return ""i'm an innocent string"")'
}}}

Another example would be a GHC-API based refactoring tool that wants to check if a refactored expression typechecks before modifying the code. If every module is imported qualified, the tool might get many false positives.

The proposal is to keep the current behaviour as the default but to add a `-fno-implicit-import-qualified` flag to disable it when needed. The following should fail to execute:

{{{
ghc -fno-implicit-import-qualified -e 'System.IO.Unsafe.unsafePerformIO (evilStuff >> return ""i'm an innocent string"")'
}}}
"	feature request	closed	normal	6.10.1	Compiler (Type checker)	6.9	fixed		gwern0@… id@…	Unknown/Multiple	Unknown/Multiple	None/Unknown	Unknown