[#188] Missing warning for nonexhaustive valbind patterns

Date:
2017-10-19 14:52 Priority:
3

State:
Closed

Submitted by:
Jackson Woodruff (jwoodruff) Assigned to:
David MacQueen (dbm)

Machine Architecture:
x86 Operating System:
All

Component:
Compiler Resolution:
Fixed

Severity:
Minor OS Version:

SML/NJ Version:
110.82 (trunk)

Keywords:
Warning

URL:

Transcript (of reproduction):

Source (for reproduction):

Summary:
Missing warning for nonexhaustive valbind patterns

Detailed description
Hi all, Currently, SMLNJ does not emit a warning for the following code: val x = fn y => let val nil = [1] in y end According to page 32, item number 3 in the definition of ML http://sml-family.org/sml97-defn.pdf, this must emit a warning informing the user that the match is invalid. A further note to this matter is that MosML and PolyML both successfully report a warning in this case. Jackson. As a precise example of what I mean: [15:50:24] Poly/ML 5.6 Release > val x = fn y => let val nil = [1] in y end;; poly: : warning: Pattern is not exhaustive. Found near val nil = [1] val x = fn: 'a -> 'a > % [15:50:40] Standard ML of New Jersey v110.79 [built: Wed Nov 2 06:06:36 2016] - val x = fn y => let val nil = [1] in y end;; val x = fn : 'a -> 'a -

Comments:

Message
Date: 2019-11-16 14:02 Sender: John Reppy This was presumably fixed when bug 130 was fixed (version 110.94)
Date: 2018-04-20 17:09 Sender: David MacQueen In 110.82 this bug is gone, and the "binding not exhaustive" warning is given. However, when executed, this example should raise the Bind exception when [1] does not match the pattern nil. It looks like the let binding has been improperly optimized away so that it is not executed. So this reveals a different bug in the optimizer, which is changing the dynamic semantics of the code.
Date: 2017-11-01 18:20 Sender: John Reppy This bug appear to be related to 130.

Field	Old Value	Date	By
status_id	Open	2019-11-16 14:02	jhr
close_date	None	2019-11-16 14:02	jhr
Resolution	Accepted As Bug	2019-11-16 14:02	jhr
assigned_to	none	2017-11-01 18:20	jhr
Operating System	None	2017-11-01 18:20	jhr
Resolution	None	2017-11-01 18:20	jhr