A strange typing error with polymorphic variants

Marc de Falco

Jake Donham

Vincent Aravantinos
 Vincent Aravantinos

Vincent Aravantinos

Jake Donham
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Date:   (:) 
From:  Vincent Aravantinos <vincent.aravantinos@g...> 
Subject:  Re: [Camllist] A strange typing error with polymorphic variants 
Oops, I pushed "send" button too early. Le 27 oct. 09 à 19:38, Vincent Aravantinos a écrit : > Le 27 oct. 09 à 19:24, Jake Donham a écrit : > >> On Tue, Oct 27, 2009 at 3:28 AM, Marc de Falco <marc@defalco.fr> >> wrote: >>> The following code : >>> type 'a p = R of 'a t  E of float >>> and 'a t = { mutable p : 'a p; c : 'a } >>> let f = >>> let x = sqrt(2.0) in >>> fun () > { c = `A; p = E 0.0 } >>> >>> generates the error : >>> The type of this expression, unit > _[> `A ] t, >>> contains type variables that cannot be generalized >>> >>> but if I change the x definition to "let x = 2.0 in" then it works. >> >> I think this is just the value restriction. The type of f is >> generalized only if the right hand side is a value (rather than an >> expression needing some computation); in your examples the one that >> fails is not a value, the others are. It looks like there is a >> relaxation to allow let bindings which are themselves values. > > With the dlambda option, the "sqrt(2.0)" version gives: > (let > (f/92 > (let (x/93 (caml_sqrt_float 2.0)) > (function param/94 (makemutable 0 [1: 0.0] 65a)))) > > whereas the "2.0" version gives: > (let (f/96 (let (x/97 2.0) (function param/98 (makemutable 0 [1: > 0.0] 65a)))) > > i.e. this last version is inlined. Do you think this can give a hint? V.