http://d.puremagic.com/issues/show_bug.cgi?id=8737
Summary: Associative Array (AA) KeyType is not Unqual-able Product: D Version: unspecified Platform: All OS/Version: All Status: NEW Severity: major Priority: P2 Component: DMD AssignedTo: nob...@puremagic.com ReportedBy: monarchdo...@gmail.com --- Comment #0 from monarchdo...@gmail.com 2012-09-29 15:42:26 PDT --- There is an issue with AA's, where it is not possible to extract the exact "mutable KeyType" of an AA. This is a built in protection for when iterating on reference keys. The problem is that it becomes impossible to create new keys, without knowing the "real" type. This was revealed in a bug in conv.to : #8705 http://d.puremagic.com/issues/show_bug.cgi?id=8705 Reduced test: -------- import std.stdio; import std.traits; import std.conv; void main() { alias short[short[short]] S; alias int[int[int]] T; S value; T result; alias Unqual!(KeyType!T) K2; // const(int)[int] alias Unqual!(ValueType!T) V2; // int foreach (k1, v1; value) { K2 k2 = to2!K2(k1); //request a cast to "const(int)[int]" !!! V2 v2 = to!V2(v1); result[k2] = v2; } } T to2(T, S)(S value) //T is const(int)[int] { alias Unqual!(KeyType!T) K2; alias Unqual!(ValueType!T) V2; Unqual!T result; foreach (k1, v1; value) { K2 k2 = to!K2(k1); //const(int) V2 v2 = to!V2(v1); //int result[k2] = v2; //Error: result[k2] isn't mutable (naturally) } return result; } -------- Here, the implementer of "foo" is unable to tranform his keys, because their types are not mutable. The real problem is that KeyType returned "const(int)[int]", is not really const, but not mutable either. Because of this Unqual doesn't work. Suggestion: The type returned by KeyType should be "full const", eg: const(int[int]). This would make it just as safe, but a user can still request an Unqual on the type. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------