From 7382948497f1ae935bd2b16596e468605a3d8033 Mon Sep 17 00:00:00 2001 From: letouzey Date: Mon, 4 Jul 2011 18:04:58 +0000 Subject: Extraction: forbid Prop-polymorphism of inductives when extracting to Ocaml A particular case in sort-polymorphism of inductive types allows an informative type (such as prod) to have instances in Prop: (I,I) : True * True : Prop This is due to the fact that prod is a singleton type: indeed (I,I) has no informative content. But this invalidates an important invariant for the correctness of the extraction: inductive constructors stop having always the same sort as their inductive type. Consider for instance: Definition f (X:Type)(x:X*X)(g:X->nat) := g (fst x). Definition test := f _ (I,I) (fun _ => 0). Then the inductive element (I,I) is extracted as a logical part __, but during a strict evaluation (i.e. in Ocaml, not Haskell), this __ will be given to fst, and hence to a match, leading to a nasty result (potentially segfault). Haskell is not affected, since fst is never evaluated. This patch adds a check for this situation during any Ocaml extraction, leading for the moment to a fatal error. Some functions in inductive.ml and retyping.ml now have an extra optional argument ?(polyprop=true) that should stay untouched in regular Coq usage, while type-checking done during extraction will disable this prop-polymorphism. git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@14256 85f007b7-540e-0410-9357-904b9bb8a0f7 --- kernel/inductive.mli | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'kernel/inductive.mli') diff --git a/kernel/inductive.mli b/kernel/inductive.mli index c14f69343..a124647c6 100644 --- a/kernel/inductive.mli +++ b/kernel/inductive.mli @@ -82,7 +82,16 @@ val check_cofix : env -> cofixpoint -> unit (** {6 Support for sort-polymorphic inductive types } *) -val type_of_inductive_knowing_parameters : +(** The "polyprop" optional argument below allows to control + the "Prop-polymorphism". By default, it is allowed. + But when "polyprop=false", the following exception is raised + when a polymorphic singleton inductive type becomes Prop due to + parameter instantiation. This is used by the Ocaml extraction, + which cannot handle (yet?) Prop-polymorphism. *) + +exception SingletonInductiveBecomesProp of identifier + +val type_of_inductive_knowing_parameters : ?polyprop:bool -> env -> one_inductive_body -> types array -> types val max_inductive_sort : sorts array -> universe -- cgit v1.2.3