Template argument of std.algorithm.iteration.chunkBy cannot access a local variable

[dlangBugzillaToGithub]

Tomoya Tanjo (@tom-tan) reported this on 2015-08-12T07:49:50Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=14909

CC List

• berni44 (@WalterBright)
• Seb
• Iain Buclaw (@ibuclaw)

Description

The following code cannot be compiled.
I checked it by using DMD trunk (v2.068-devel-407dac3) in Mac OSX.

---
import std.algorithm.iteration;

void main()
{
    auto n = 3;
    auto s = [1,2,3].chunkBy!(a => a+n); ///  Error: function sample.main.ChunkByImpl!(__lambda1, int[]).ChunkByImpl.__lambda12 cannot access frame of function D main
}
---

[dlangBugzillaToGithub]

dlang-bot commented on 2020-09-10T19:11:02Z

@jamesragray created dlang/phobos pull request #7625 "Issue 14909: Provided a fix for the forward range version of chunkBy …" mentioning this issue:

- Issue 14909: Provided a fix for the forward range version of chunkBy so that it can accept predicates refernce variables in the calling function

https://github.com/dlang/phobos/pull/7625

[dlangBugzillaToGithub]

dlang-bot commented on 2020-09-23T01:05:20Z

dlang/phobos pull request #7625 "Issue 14909: Provided a fix for the forward range version of chunkBy …" was merged into master:

- 2ed6952a719ce610bc3a513d67b602163f196ff9 by James Gray:
  Issue 14909: Provided a fix for the forward range version of chunkBy so that it can accept predicates refernce variables in the calling function

https://github.com/dlang/phobos/pull/7625

[dlangBugzillaToGithub]

ibuclaw (@ibuclaw) commented on 2021-08-23T14:11:51Z

Possibly reduced test:
---
template binaryFun(alias fun)
{
    alias binaryFun = fun;
}

struct ChunkByImpl(alias pred, Range)
{
    alias eq = binaryFun!((a, b) => pred(a));
    Range r;
    this(Range )
    {
        eq(r, r);
    }
}

auto chunkBy(alias pred, Range)(Range)
{
    ChunkByImpl!(pred, Range);
}

void main()
{
    auto n = 3;
    1.chunkBy!(a => a+n);
}