Re: [GHC] #10460: Allow foreign prim to return Any

#10460: Allow foreign prim to return Any -------------------------------------+------------------------------------- Reporter: ezyang | Owner: ezyang Type: feature request | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler (Type | Version: 7.11 checker) | Keywords: Resolution: | Architecture: Operating System: Unknown/Multiple | Unknown/Multiple Type of failure: GHC rejects | Test Case: valid program | Blocking: Blocked By: | Differential Revisions: Related Tickets: | -------------------------------------+------------------------------------- Changes (by ezyang): * owner: => ezyang Old description:

Presently, we have

{{{ {-# LANGUAGE GHCForeignImportPrim #-} module Serum where import GHC.Exts

foreign import prim "chenycopy" cheneycopy :: Any -> Any }}}

induces the error

{{{ Serum.hs:5:1: Unacceptable result type in foreign declaration: ‘Any’ cannot be marshalled in a foreign call When checking declaration: foreign import prim safe "static chenycopy" cheneycopy :: Any -> Any }}}

We ought to allow a lifted value to be returned from a foreign primop; no reason not to, anyway; no reason not to, and there are plenty of built-in primops which do this.

For reference, lifted arguments were allowed in arugments in this commit:

{{{ commit e29001c9e0f73885c0b85d86c3a854519448013a Author: Joachim Breitner Mon Mar 12 01:20:12 2012 Committer: Simon Marlow Wed Mar 14 06:01:18 2012

Allow Any as an argument type to foreign prim functions }}}

New description: Presently, we have {{{ {-# LANGUAGE GHCForeignImportPrim #-} module Serum where import GHC.Exts foreign import prim "chenycopy" cheneycopy :: Any -> Any }}} induces the error {{{ Serum.hs:5:1: Unacceptable result type in foreign declaration: ‘Any’ cannot be marshalled in a foreign call When checking declaration: foreign import prim safe "static chenycopy" cheneycopy :: Any -> Any }}} We ought to allow a lifted value to be returned from a foreign primop; no reason not to, anyway; no reason not to, and there are plenty of built-in primops which do this. For reference, lifted arguments were allowed in arugments in this commit: {{{ commit e29001c9e0f73885c0b85d86c3a854519448013a Author: Joachim Breitner Mon Mar 12 01:20:12 2012 Committer: Simon Marlow Wed Mar 14 06:01:18 2012 Allow Any as an argument type to foreign prim functions }}} I can volunteer to write the patch but it would be good if someone else OKs this before I proceed. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10460#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler