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pattern matching problem with GADT #5332

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vicuna opened this Issue Aug 9, 2011 · 1 comment

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vicuna commented Aug 9, 2011

Original bug ID: 5332
Reporter: @diml
Status: closed (set by @garrigue on 2011-08-09T14:01:47Z)
Resolution: fixed
Priority: normal
Severity: minor
Fixed in version: 3.13.0+dev
Category: ~DO NOT USE (was: OCaml general)

Bug description

I was playing with the svn version of ocaml and get the following error:

type ('env, 'a) var =
| Zero : ('a * 'env, 'a) var
| Succ : ('env, 'a) var -> ('b * 'env, 'a) var

type ('env, 'a) typ =
| Tint : ('env, int) typ
| Tbool : ('env, bool) typ
| Tvar : ('env, 'a) var -> ('env, 'a) typ

let f : type env a. (env, a) typ -> (env, a) typ -> int = fun ta tb ->
match ta, tb with
| Tint, Tint -> 0
| Tbool, Tbool -> 1
| Tvar var, tb -> 2

let x = f Tint (Tvar Zero)

Here i get no warning when defining f, and x is evaluated to 0. If i remove the Tbool constructor, then i get a warning and a Match_failure exception.

@vicuna

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vicuna commented Aug 9, 2011

Comment author: @garrigue

Stupid bug in the auxiliary function Parmatch.combinations.

Thanks for your report.

@vicuna vicuna closed this Aug 9, 2011

@vicuna vicuna added the bug label Mar 20, 2019

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