There is currently no way to test whether a particular symbol is going to be introduced. It might be worthwhile to investigate whether this could be part of getFunctionAttributes (https://dlang.org/spec/traits.html#getFunctionAttributes). See also: https://issues.dlang.org/show_bug.cgi?id=17791
PR : https://github.com/dlang/dmd/pull/7232
Commits pushed to master at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/03b13c79cb98088c60faa2457db0d8f85a0bc6dc Fix Issue 17878 - Add __traits(isFuture, ...) https://github.com/dlang/dmd/commit/51bc2fb427a5e0b3701b11ab2b6a5f356d8eca5d Merge pull request #7232 from RazvanN7/Issue_17878 Fix Issue 17878 - Add __traits(isFuture, ...)
Commits pushed to stable at https://github.com/dlang/dmd https://github.com/dlang/dmd/commit/03b13c79cb98088c60faa2457db0d8f85a0bc6dc Fix Issue 17878 - Add __traits(isFuture, ...) https://github.com/dlang/dmd/commit/51bc2fb427a5e0b3701b11ab2b6a5f356d8eca5d Merge pull request #7232 from RazvanN7/Issue_17878
dlang/dmd pull request #12093 "[dmd-cxx] Backport more recent traits to the C++ port" was merged into dmd-cxx: - 18da3ec2cbe528f546ab3fc955662457fb0a81e1 by RazvanN7: [dmd-cxx] Fix Issue 17878 - Add __traits(isFuture, ...) https://github.com/dlang/dmd/pull/12093