Bug 18135 – [REG2.078] can't join RegexMatch anymore

This used to compile, it doesn't anymore with 2.078.0: ``` import std.algorithm : joiner, map; auto matchIssueRefs(string message) { import std.regex; static auto matchToRefs(M)(M m) { enum splitRE = regex(`foo`); return m.captures[0].splitter(splitRE); } enum issueRE = ctRegex!`foo`; return message.matchAll(issueRE).map!matchToRefs; } auto getIssueRefs(string[] commits) { return commits .map!matchIssueRefs .joiner; } ``` with: ``` /home/seb/dlang/phobos/std/algorithm/iteration.d(2504): Error: cannot modify struct this._current MapResult!(matchToRefs, RegexMatch!string) with immutable members test.d(21): Error: template instance std.algorithm.iteration.joiner!(MapResult!(matchIssueRefs, string[])) error instantiating ```

This was introduced by https://github.com/dlang/phobos/pull/4286

See also: https://issues.dlang.org/show_bug.cgi?id=17066

The referenced std.regex change is from 2016-12 and was reverted in the meantime. Digger pointed me to https://github.com/dlang/phobos/pull/5722 instead.

cat > bug.d << CODE import std.regex : RegexMatch; struct MapResult(Range) { Range input; } void bug() { MapResult!(RegexMatch!string) res; res = MapResult!(RegexMatch!string)(); } CODE dmd -c bug.d ---- bug.d(11): Error: cannot modify struct res MapResult!(RegexMatch!string) with immutable members ----

Commits pushed to stable at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/b221120735b04095a6d4c7702eb9cc6e37aba170 fix Issue 18135 - can't join RegexMatch anymore - fix copying of structs with RegexMatch fields by making const interface reference rebindable https://github.com/dlang/phobos/commit/8c19c30d239f034c14ec21d216ccf26ee136db61 Merge pull request #5972 from MartinNowak/fix18135 fix Issue 18135 - can't join RegexMatch anymore merged-on-behalf-of: Sebastian Wilzbach <[email protected]>

Commits pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/b221120735b04095a6d4c7702eb9cc6e37aba170 fix Issue 18135 - can't join RegexMatch anymore https://github.com/dlang/phobos/commit/8c19c30d239f034c14ec21d216ccf26ee136db61 Merge pull request #5972 from MartinNowak/fix18135