Haskell › Haskell - Glasgow-haskell-bugs

[GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

Classic

List

Threaded

6 messages Options

GHC

[GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

#6005: Template Haskell disallows use of promoted data constructor in same splice
---------------------------------------+------------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Component: Template Haskell
Version: 7.5 | Keywords: DataKinds PolyKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Testcase:
Blockedby: | Blocking:
Related: |
---------------------------------------+------------------------------------
The following code fails to compile under GHC 7.5.20120413:

{{{
{-# LANGUAGE TemplateHaskell, DataKinds, PolyKinds #-}

$( [d|
data Nat = Zero | Succ Nat
data Proxy a = Proxy
foo :: Proxy Zero
foo = Proxy
|])
}}}

The error is:
{{{
The exact Name `Zero_a3N3' is not in scope
Probable cause: you used a unique name (NameU), perhaps via newName,
in Template Haskell, but did not bind it
If that's it, then -ddump-splices might be useful
}}}

Using {{{-ddump-splices}}} shows that the same internal name is used for
the data constructor at declaration and usage.

The problem seems to be that a data constructor declared within a splice
cannot be used as a promoted type in that same splice. Separating the
splices works.

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6005>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

_______________________________________________
Glasgow-haskell-bugs mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

GHC

Re: [GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

#6005: Template Haskell disallows use of promoted data constructor in same splice
---------------------------------------+------------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Component: Template Haskell
Version: 7.5 | Keywords: DataKinds PolyKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Testcase:
Blockedby: | Blocking:
Related: |
---------------------------------------+------------------------------------

Comment(by simonpj@…):

commit 2a1190431218f838797be3c09084e22dc131c58a
{{{
Author: Simon Peyton Jones <[hidden email]>
Date: Wed Apr 25 12:55:41 2012 +0100

Fix looking up of Exact RdrNames, fixes Trac #6005

See Note [Splicing Exact names] in RnEnv.

compiler/rename/RnEnv.lhs | 43
++++++++++++++++++++++++++++++++++---------
1 files changed, 34 insertions(+), 9 deletions(-)
}}}

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6005#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

_______________________________________________
Glasgow-haskell-bugs mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

GHC

Re: [GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

In reply to this post by GHC

GHC

Re: [GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

In reply to this post by GHC

#6005: Template Haskell disallows use of promoted data constructor in same splice
----------------------------------------+-----------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Template Haskell | Version: 7.5
Resolution: | Keywords: DataKinds PolyKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Difficulty: Unknown
Testcase: th/T6005 | Blockedby:
Blocking: | Related:
----------------------------------------+-----------------------------------
Changes (by goldfire):

* status: closed => new
* resolution: fixed =>

Comment:

Thanks for applying this fix. Unfortunately, the following case still
fails:

{{{
$( [d|
data Nat = Zero | Succ Nat deriving Show
data Proxy a = Proxy
foo :: Proxy Zero
foo = Proxy
|])
}}}

The only difference between this case and the original is the {{{deriving
Show}}}.

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6005#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

_______________________________________________
Glasgow-haskell-bugs mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

GHC

Re: [GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

In reply to this post by GHC

#6005: Template Haskell disallows use of promoted data constructor in same splice
----------------------------------------+-----------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Template Haskell | Version: 7.5
Resolution: fixed | Keywords: DataKinds PolyKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Difficulty: Unknown
Testcase: th/T6005, T6005a | Blockedby:
Blocking: | Related:
----------------------------------------+-----------------------------------
Changes (by simonpj):

* status: new => closed
* testcase: th/T6005 => th/T6005, T6005a
* resolution: => fixed

Comment:

This turns out to be unrelated to data kinds etc. Instead it is simply to
do with the difficulty of type-checking Template Haskell brackets,
something that led me to propose a
[http://hackage.haskell.org/trac/ghc/blog/Template%20Haskell%20Proposal
complete overhaul] (not yet done).

In this case we are generating the derived code for the bracket when we
typecheck the bracket. This is silly because it's sure to type check; and
it goes wrong too for reasons that are not intersting.

I have brutally simply suppressed all 'deriving' processing inside TH
brackets. It'll all become irrelevant with the overhaul.

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6005#comment:4>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

_______________________________________________
Glasgow-haskell-bugs mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs

GHC

Re: [GHC] #6005: Template Haskell disallows use of promoted data constructor in same splice

In reply to this post by GHC

#6005: Template Haskell disallows use of promoted data constructor in same splice
----------------------------------------+-----------------------------------
Reporter: goldfire | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Template Haskell | Version: 7.5
Resolution: fixed | Keywords: DataKinds PolyKinds
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: GHC rejects valid program | Difficulty: Unknown
Testcase: th/T6005, T6005a | Blockedby:
Blocking: | Related:
----------------------------------------+-----------------------------------

Comment(by simonpj@…):

commit d50cb3eda3912df0d75a8177f04783689b21dc9b
{{{
Author: Simon Peyton Jones <[hidden email]>
Date: Thu Apr 26 13:47:54 2012 +0100

Do not generate derived instances in TH brackets

See Note [Deriving inside TH brackets] in TcInstDcls
Fixes Trac #6005 (again)

compiler/typecheck/TcInstDcls.lhs | 23 ++++++++++++++++++++++-
1 files changed, 22 insertions(+), 1 deletions(-)
}}}

--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6005#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler

_______________________________________________
Glasgow-haskell-bugs mailing list
[hidden email]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs