FW: [Haskell-cafe] Significant changes in -Wall for GHC 7.10

Edward Z. Yang ezyang at mit.edu
Tue May 5 15:44:26 UTC 2015

There were a few refactorings of DynFlags from the 7.8-7.10
cycle, I bet one of them broke -Wall. I'm bisecting.


Excerpts from Simon Peyton Jones's message of 2015-05-05 08:01:16 -0700:
> GHC devs,
> I wasn’t aware that we’d changed these.  Anyone know why?
> Simon
> From: Haskell-Cafe [mailto:haskell-cafe-bounces at haskell.org] On Behalf Of Omari Norman
> Sent: 05 May 2015 15:55
> To: haskell Cafe
> Subject: [Haskell-cafe] Significant changes in -Wall for GHC 7.10
> I noticed some significant changes to the flags included with -Wall in GHC 7.10.  Many flags that were previously included in -Wall are now not included.  These include:
> -fwarn-type-defaults
> -fwarn-name-shadowing
> -fwarn-missing-signatures
> -fwarn-hi-shadowing
> -fwarn-orphans
> -fwarn-unused-do-bind
> -fwarn-trustworthy-safe
> I can't find any mention in the release notes of this change in behavior.
> I was wondering what the rationale is for these changes?  Any link to relevant discussion would be appreciated if it exists.
> Also, what opinion do people have?  I previously kept my code -Wall clean, but sometimes that would be a pain.  For instance I would munge local names so they wouldn't trigger -fwarn-name-shadowing, and I would add signatures to integers so they wouldn't trigger -fwarn-type-defaults.  In fact, I only noticed this change in behavior in 7.10 because I was considering dumping -Wall, and when I looked at the 7.10 manual I saw that it does not enable -fwarn-name-shadowing.  (I still use 7.8 but Google pulled the 7.10 manual.)  Does this change indicate that people were finding -Wall too onerous and, thus, not using it?
> I do remember reading complaints about -fwarn-unused-do-bind being added to -Wall, but I previously felt dirty about name shadowing though I wondered if munging names to avoid shadowing was actually worse.
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