Source Location of DataCon objects in GHC 7.4.1 API

Simon Peyton-Jones simonpj at microsoft.com
Tue Jun 5 14:49:41 CEST 2012


That's our policy too, as you will see if you look at any closed Trac ticket.  We have thousands of regression tests, and they are fabulously useful.  But it's a judgement call when the scope is extremely narrow and the regression test is hard to make, and I decided not to.  

By all means submit a regression test for this one; I'll gladly commit it.

S 

| -----Original Message-----
| From: Jacques Carette [mailto:carette at mcmaster.ca]
| Sent: 05 June 2012 13:45
| To: Simon Peyton-Jones
| Cc: JP Moresmau; glasgow-haskell-users at haskell.org
| Subject: Re: Source Location of DataCon objects in GHC 7.4.1 API
| 
| One bit of experience from my Maple days: we made it a policy to create
| regression tests for every single bug we fixed.  No bug could be marked
| closed without an identifier for the test that makes sure this does not
| revert.
| 
| This seemed like too much at first, but over the years, we were always
| glad of this.  We caught all sorts of very strange bugs because of doing
| this.  This is especially valuable for very long-lived software (like
| GHC), where the time-span between the last time the problem showed up
| and when it occurs again can be 15+ years.
| 
| In other words, I am saying that even though in the present context this
| feature/bug can seem small, it is extremely hard to predict what context
| will be true in 10+ years, where this regression may become a symptom of
| something bigger.
| 
| Jacques
| 
| On 05/06/2012 8:36 AM, Simon Peyton-Jones wrote:
| > Done.  I don't think it's worth a regression test.
| >
| > SImon
| >
| > commit cb705a38d677e2ab4cad37447c8180bd397d5576
| > Author: Simon Peyton Jones<simonpj at microsoft.com>
| > Date:   Tue Jun 5 13:35:07 2012 +0100
| >
| >      Add sensible locations to record-selector bindings
| >
| >   compiler/typecheck/TcTyClsDecls.lhs |   26 +++++++++++++------------
| -
| >   1 files changed, 13 insertions(+), 13 deletions(-)
| >
| > | -----Original Message-----
| > | From: glasgow-haskell-users-bounces at haskell.org
| > | [mailto:glasgow-haskell- users-bounces at haskell.org] On Behalf Of
| > | Simon Peyton-Jones
| > | Sent: 05 June 2012 12:38
| > | To: JP Moresmau; glasgow-haskell-users at haskell.org
| > | Subject: RE: Source Location of DataCon objects in GHC 7.4.1 API
| > |
| > | Ah I see.  I'm fixing this.
| > |
| > | Simon
| > |
| > | | -----Original Message-----
| > | | From: glasgow-haskell-users-bounces at haskell.org
| > | | [mailto:glasgow-haskell- users-bounces at haskell.org] On Behalf Of
| > | | JP Moresmau
| > | | Sent: 01 June 2012 10:25
| > | | To: glasgow-haskell-users at haskell.org
| > | | Subject: Source Location of DataCon objects in GHC 7.4.1 API
| > | |
| > | | Hello
| > | |
| > | | I have a failing test in BuildWrapper when moving from GHC 7.0.4
| > | | to 7.4.1. As far I can tell, in the TypecheckedSource I get
| > | | DataCon objects that have no location info, and hence I can't
| > | | retrieve them by location... Which is useful in a IDE (tell me
| > | | what's under my mouse cursor, tell me where else it's used).
| > | |
| > | | Given the simple data declaration:
| > | | data DataT=MkData {name :: String}
| > | |
| > | | In 7.0.4 I obtain a hierarchy that ends in FunBind (on a Var
| > | | called "name")/MatchGroup/Match/ConPatOut and the contained
| > | | DataCon named "MkData" has a SrcSpan associated with it, and so do
| > | | the Var, MatchGroup and Match.
| > | | In 7.4.1 I have the same hierarchy but the DataCon tells me "no
| > | | location info". The Var "name" has a location, but the MatchGroup
| > | | and Match don't either.
| > | |
| > | | Is it a normal change? Do I need to change something in the way I
| > | | load the module? Is it a regression?
| > | |
| > | | Thanks!
| > | |
| > | | --
| > | | JP Moresmau
| > | | http://jpmoresmau.blogspot.com/
| > | |
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| > |
| > |
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