0005939: "fun (type t) when cond -> ..." should be rejected, maybe also "fun p when cond -> ..."

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0005939

OCaml

OCaml general

public

2013-03-06 18:56

2013-04-29 16:34

Reporter

frisch

Assigned To

doligez

Priority

normal

Severity

minor

Reproducibility

have not tried

Status

confirmed

Resolution

open

Platform

OS Version

Product Version

Target Version

4.02.0+dev

Fixed in Version

Summary

0005939: "fun (type t) when cond -> ..." should be rejected, maybe also "fun p when cond -> ..."

Description

I found the following when trying to clean up the Parsetree by putting Pexp_when clauses where they belong in the AST:

# fun (type t) when false -> 0;;
>> Fatal error: exit(0) outside appropriated catch
Fatal error: exception Misc.Fatal_error

The fix is not difficult (either in the parser or in the type-checker). But I'm wondering whether it make sense to keep the syntax:

fun pat when cond -> ...

which necessarily triggers warning 25 (bad style, all clauses in this pattern-matching are guarded).

The Parsetree cleanup would be a little bit simpler if we got rid of this form as well. I doubt anyone uses it. I propose to get rid of it, after (i) asking on the caml-list if anyone objects; (ii) using OPAM to check that the construction is indeed not used in any of the packaged software.

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0005936

confirmed

Weird syntax accepted by OCaml

Notes
(0009085) frisch (developer) 2013-04-12 13:51	0005936 seems to confirm that "fun pat when cond -> expr" can be removed with no harm.

(0009113) frisch (developer) 2013-04-15 18:24	Commit 13528 on branch extension_points introduces an explicit representation of "cases" with an optional guard in order to get rid of the ugly Pexp_when. It also remove support for the construction "fun pat when cond -> expr". So, please don't remove it from the trunk, this will be part of the merge of extension_points.

(0009226) frisch (developer) 2013-04-29 16:34	Setting Target Version = 4.02 (already fixed in extension_points, which will hopefully be merged in time for 4.02).

Issue History
Date Modified	Username	Field	Change
2013-03-06 18:56	frisch	New Issue
2013-03-07 15:50	doligez	Status	new => confirmed
2013-04-12 13:49	frisch	Relationship added	related to 0005936
2013-04-12 13:51	frisch	Note Added: 0009085
2013-04-15 18:24	frisch	Note Added: 0009113
2013-04-25 17:05	doligez	Assigned To	=> doligez
2013-04-25 17:05	doligez	Status	confirmed => assigned
2013-04-25 17:06	doligez	Status	assigned => confirmed
2013-04-29 16:34	frisch	Note Added: 0009226
2013-04-29 16:34	frisch	Target Version	=> 4.02.0+dev