digitalmars.D.bugs - [Issue 19926] New: Wrong instantiation of opDispatch when used in
- d-bugmail puremagic.com (55/55) May 31 2019 https://issues.dlang.org/show_bug.cgi?id=19926
https://issues.dlang.org/show_bug.cgi?id=19926 Issue ID: 19926 Summary: Wrong instantiation of opDispatch when used in WithStatement Product: D Version: D2 Hardware: x86 OS: Windows Status: NEW Severity: normal Priority: P1 Component: dmd Assignee: nobody puremagic.com Reporter: simen.kjaras gmail.com DMD is of two minds when invoking opDispatch inside WithStatements, and requires that the template be possible to instantiate with the arguments passed, followed by instatiating it with an empty parameter tuple: unittest { with (S1.init) { a(1); // Compiles } with (S2.init) { a(1); // is not callable using argument types (int) } } struct S1 { auto opDispatch(string name, Args...)(Args args) { static assert(Args.length == 0); return (int i){}; } } struct S2 { auto opDispatch(string name)() { return (int i){}; } } As the example with S2 shows, the compiler complains when opDispatch takes no parameters (this is sensible). However, as S1 shows, Args is actually empty when opDispatch is instantiated, and instead opDispatch needs to return a lambda that actually handles the run-time arguments (this is not sensible, on more than one level). The correct behavior would of course be for this to compile and run: unittest { with (S3.init) { a(1); } } struct S3 { auto opDispatch(string name, Args...)(Args args) { static assert(Args.length == 1); static assert(is(Args[0] == int)); assert(args[0] == 1); } } --
May 31 2019