Language level heads-up warnings

[Simon Peyton-Jones]

I'm just saying that GHC has to be able to check while compiling one module, ie as now.  (It can see details of the things it imports, obviously, since it needs to know that to compile the module)

| -----Original Message-----
| From: David Luposchainsky [mailto:dluposchainsky at googlemail.com]
| Sent: 22 May 2013 14:54
| To: ghc-devs at haskell.org
| Cc: Simon Peyton-Jones
| Subject: Re: Language level heads-up warnings
| 
| On 2013-05-22 15:42, Simon Peyton-Jones wrote:
| > Yes, I think that if the libraries community thought it was
| > important, I (or indeed someone else) could add a couple of ad-hoc
| > warnings to GHC without much work. But you'd all need to be clear and
| > specific about what warnings were wanted, and they'd need to be easy
| > to check (ie no global program analysis).
| 
| Simon,
| 
| good to hear that it's worth thinking about.
| 
| I'm not sure what exactly "no global program analysis" means here. Where
| would the boundaries of such warnings be? I could imagine problems if
| Applicative/Monad are defined in separate packages/modules (although
| that may be rare in practice).
| 
| Greetings,
| David