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Missing parentheses when printing polymorphic variant value in non exhaustivity warning #6680

vicuna opened this issue Nov 28, 2014 · 2 comments


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commented Nov 28, 2014

Original bug ID: 6680
Reporter: pveber
Assigned to: @garrigue
Status: closed (set by @xavierleroy on 2016-12-07T10:37:05Z)
Resolution: fixed
Priority: normal
Severity: minor
Version: 4.02.1
Fixed in version: 4.02.2+dev / +rc1
Category: typing

Bug description

In the following, the counter-example produced by the exhaustivity check is not printed correctly:

    OCaml version 4.02.1

let f = function a (b 1) -> true;;

Warning 8: this pattern-matching is not exhaustive.
Here is an example of a value that is not matched:
a b 0
val f : [< a of [< b of int ] ] -> bool =

a b 0 should be a (b 0)

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commented Nov 28, 2014

Comment author: @gasche

The easy way to fix this is to fix the code of the pretty_* functions in typing/ A simple patch is attached that fixes the reported issue.

The good way to fix this, in my opinion, is to have this code not pretty-print a value extrapolated from a pattern, but to extrapolate this value into a valid AST tree, and then call the Pprintast functions to print expressions and handle the ugly details of pretty-printings. Pprintast is not a bug-free zone, but we could at least centralize our pretty-printing bugs in a single place.


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commented Dec 8, 2014

Comment author: @garrigue

Fixed in trunk and 4.02 are revisions 15640 and 15641.

@vicuna vicuna closed this Dec 7, 2016

@vicuna vicuna added the typing label Mar 14, 2019

@vicuna vicuna added the bug label Mar 20, 2019

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