https://issues.dlang.org/show_bug.cgi?id=15811
--- Comment #1 from Kenji Hara <k.hara...@gmail.com> --- Note: I've used following test case. void foo(string text) { import std.conv; auto s = text; assert(s == "a"); } void main() { foo("a"); } If assert succeeds, new lookup rule is used. Otherwise old lookup rule is used. --