Bug 7110 – opSlice() & opIndex functions works unstable as template arguments

--- struct S { } struct Call { static S opSlice() { return S(); } static S opIndex(size_t) { return S(); } } template Template(Args...) { static assert(is(typeof(Args[0]) == S)); } alias Template!(S()) A0; // passes alias Template!(Call.opSlice()) A1; // passes alias Template!(Call.opIndex(0)) A2; // passes alias Template!(Call[]) A3; // failes alias Template!(Call[0]) A4; // failes ---

I believe this is invalid - here Call[] is a dynamic array of Call, and Call[0] is a static array of Call, length zero. You can work around this using: ---- alias Template!({ return Call[]; }()) A3; alias Template!({ return Call[0]; }()) A4; ----

Thanks! I'm completely wrong here.

And an easier workaround: --- alias Template!((Call[])) A3; // passes alias Template!((Call[0])) A4; // passes --- But isn't it strange? Looks like this workaround is a bug. It leads to things like this: --- struct S { int opSlice(int, int) const { return 0; } int opSlice() const { return 0; } int opIndex(int, int) const { return 0; } int opIndex(int) const { return 0; } } enum e = S(); template T(alias a) { } // or T(a...) alias T!( S ) T0; // passes alias T!((S)) T1; // passes alias T!( S()[0..0] ) A0; // passes alias T!( (e[0..0]) ) A1; // passes alias T!( e[0..0] ) A2; // passes alias T!( S()[0, 0] ) B0; // passes alias T!( (e[0, 0]) ) B1; // passes alias T!( e[0, 0] ) B2; // passes alias T!( S()[] ) C0; // passes alias T!( (e[]) ) C1; // passes alias T!( e[] ) C2; // fails: e is used as a type alias T!( S()[0] ) D0; // passes alias T!( (e[0]) ) D1; // passes alias T!( e[0] ) D2; // fails: e must be an array or pointer type, not S --- And the last error message looks wrong.

Commit pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/28edc2597a9f1e802e3a2e18353b3038a5307ac5 Merge pull request #784 from 9rnsr/fix7110 Issue 7110 - opSlice() & opIndex functions works unstable as template arguments