October 18, 2019
https://issues.dlang.org/show_bug.cgi?id=20306

          Issue ID: 20306
           Summary: incomplete mixin type with a lambda
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: destructionator@gmail.com

void test(a...)() {}

void main() {
        test!(a => 0);
        test!(mixin("a => 0"));
}


Notice the first one working, but then mixin the same code fails with

bug.d(5): Error: incomplete mixin type a => 0

on new dmd, used to work until very recently.

Up to      2.087.1: Success and no output
Since      2.088.0: Failure with output: onlineapp.d(5): Error: incomplete
mixin type `a => 0`


still works on the ldc and gdc versions I have here on my computer.

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