0005267: camlp4r (?) does not respect the constructor's arity

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Date Submitted

Last Update

0005267

OCaml

Camlp4

public

2011-05-17 07:49

2012-09-20 16:19

Reporter

Dmitry Grebeniuk

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

acknowledged

Resolution

open

Platform

OS Version

Product Version

3.13.0+dev

Target Version

4.01.0+dev

Fixed in Version

Summary

0005267: camlp4r (?) does not respect the constructor's arity

Description

# type t1 = [ A of int ];
type t1 = [ A of int ]
# fun [ A "a" True -> () ];
Characters 6-16:
  fun [ A "a" True -> () ];
        ^^^^^^^^^^
Error: This pattern matches values of type (string * bool)
       but a pattern was expected which matches values of type int

The error here should be more like to "Error: The constructor A expects 1 argument(s), but is applied here to 2 argument(s)"

Maybe this is a minor issue itself, but it leads to very hard to find errors when the wrong type infers from pattern matching and spreads all over the code:

# type t 'a = [ T of 'a ];
type t 'a = [ T of 'a ]
# value f x = match x with [ T a b -> a ];
value f : t ('a * 'b) -> 'a = <fun>

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Notes
(0007687) doligez (manager) 2012-07-10 15:09	This is not really a camlp4 problem, because the compiler does automatic tuplification of constructor arguments when you pass several arguments to a unary constructor: $ ocaml Objective Caml version 3.12.1 # type t1 = A of int;; type t1 = A of int # function A ("a", true) -> ();; Error: This pattern matches values of type string * bool but a pattern was expected which matches values of type int #

(0008128) doligez (manager) 2012-09-20 16:19	Definitely not a camlp4 problem. We could have a better error message for the first example, but there's nothing we can do to prevent propagation in the second example.

Issue History
Date Modified	Username	Field	Change
2011-05-17 07:49	Dmitry Grebeniuk	New Issue
2011-05-17 07:49	Dmitry Grebeniuk	Status	new => assigned
2011-05-17 07:49	Dmitry Grebeniuk	Assigned To	=> ertai
2011-10-26 08:35	ertai	Assigned To	ertai => xclerc
2012-07-10 15:09	doligez	Note Added: 0007687
2012-07-10 15:09	doligez	Target Version	=> 4.01.0+dev
2012-07-31 13:36	doligez	Target Version	4.01.0+dev => 4.00.1+dev
2012-09-20 16:19	doligez	Note Added: 0008128
2012-09-20 16:19	doligez	Assigned To	xclerc =>
2012-09-20 16:19	doligez	Status	assigned => acknowledged
2012-09-20 16:19	doligez	Target Version	4.00.1+dev => 4.01.0+dev