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Bug 12189 – "out" parameters should be allowed to modify immutable values in ctors

Status: RESOLVED
Resolution: INVALID
Severity: enhancement
Priority: P2
Component: dmd
Product: D
Version: D2
Platform: All
OS: All
Creation time: 2014-02-17T17:56:00Z
Last change time: 2014-02-19T01:10:59Z
Assigned to: nobody
Creator: dlang-bugzilla

Comments

Comment #0 by dlang-bugzilla — 2014-02-17T17:56:13Z

void initialize(out string[] v) { v = ["Hi!"]; } immutable string[] s; shared static this() { s = ["Hi!"]; // OK initialize(s); // NG }

Comment #1 by timon.gehr — 2014-02-18T04:08:29Z

string[]* ms; void initialize(out string[] v){ v = ["Hi!"]; ms = &v; // oops }

Comment #2 by k.hara.pg — 2014-02-18T20:10:06Z

As Timon shows, accepting variable initialization via out parameter will make a hole in type system, because out parameter should have mutable type. So this is impossible enhancement.

Comment #3 by dlang-bugzilla — 2014-02-18T20:46:46Z

Thanks, I didn't think about that. If "out" did not allow escaping references then I guess it would be different.

Comment #4 by bearophile_hugs — 2014-02-19T01:10:59Z

(In reply to comment #3) > If "out" did not allow escaping references then I guess it would be different. "scope out"?