Re: Reify and separating renamer+TH from type-checking

[Edward Kmett]

Worse, 'reify' is in many cases the very reason why folks are using
template-haskell in the first place to build instances or classes based on
properties of data types above the splice in the current module.

On Fri, Jan 8, 2016 at 2:40 PM, Edward Z. Yang  wrote:

> I implemented the refactoring to run the renamer and TH splices all
> first before doing any type-checking, but actually there's a problem:
> Template Haskell splices can call 'reify', which needs the type
> information in order to supply the information about the identifiers
> in question.  I can't think of any good way around this problem.
>
> Edward
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Re: Reify and separating renamer+TH from type-checking

[Jacques Carette]

FYI, metaocaml runs into the same problem [for different reasons].  
There the design decision was to not allow using a data-type in the same 
file as its definition. Separate compilation then solves the problem.


This is a minor pain.  But in Haskell, this would lead to orphan 
instances when using TH to derive instances, which is likely to be 
thought of as a rather bigger pain.


Jacques

On 2016-01-08 6:08 PM, Simon Peyton Jones wrote:

Bother.  That's true.  And it's a vital feature.  Otherwise how do we do

data T = T1 | T2
$(makeLenses 'T)

So we can't separate the two after all.  Sorry -- I totally forgot about that. 
Very annoying.

Simon

| -Original Message-
| From: Edward Z. Yang [mailto:ezy...@mit.edu]
| Sent: 08 January 2016 19:40
| To: Simon Peyton Jones <simo...@microsoft.com>
| Cc: ghc-devs <ghc-devs@haskell.org>
| Subject: Reify and separating renamer+TH from type-checking
|
| I implemented the refactoring to run the renamer and TH splices all
| first before doing any type-checking, but actually there's a problem:
| Template Haskell splices can call 'reify', which needs the type
| information in order to supply the information about the identifiers
| in question.  I can't think of any good way around this problem.
|
| Edward
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Reify and separating renamer+TH from type-checking

[Edward Z. Yang]

I implemented the refactoring to run the renamer and TH splices all
first before doing any type-checking, but actually there's a problem:
Template Haskell splices can call 'reify', which needs the type
information in order to supply the information about the identifiers
in question.  I can't think of any good way around this problem.

Edward
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Re: Reify and separating renamer+TH from type-checking

[David Kraeutmann]

I think I ran into this issue when we had the Safe Haskell annotation bug, 
which is why I just disabled annotations for SH. I can't think of a way around 
it unless we change the TH spec.

On 1/8/2016 8:40 PM, Edward Z. Yang wrote:
> I implemented the refactoring to run the renamer and TH splices all
> first before doing any type-checking, but actually there's a problem:
> Template Haskell splices can call 'reify', which needs the type
> information in order to supply the information about the identifiers
> in question.  I can't think of any good way around this problem.
>
> Edward
> ___
> ghc-devs mailing list
> ghc-devs@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>




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RE: Reify and separating renamer+TH from type-checking

[Simon Peyton Jones]

Bother.  That's true.  And it's a vital feature.  Otherwise how do we do

data T = T1 | T2
$(makeLenses 'T)

So we can't separate the two after all.  Sorry -- I totally forgot about that. 
Very annoying.

Simon

| -Original Message-
| From: Edward Z. Yang [mailto:ezy...@mit.edu]
| Sent: 08 January 2016 19:40
| To: Simon Peyton Jones <simo...@microsoft.com>
| Cc: ghc-devs <ghc-devs@haskell.org>
| Subject: Reify and separating renamer+TH from type-checking
| 
| I implemented the refactoring to run the renamer and TH splices all
| first before doing any type-checking, but actually there's a problem:
| Template Haskell splices can call 'reify', which needs the type
| information in order to supply the information about the identifiers
| in question.  I can't think of any good way around this problem.
| 
| Edward
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