https://issues.dlang.org/show_bug.cgi?id=23817

          Issue ID: 23817
           Summary: Reject `is` alias template instance TypeSpecialization
                    when TemplateParameterList supplied
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: nick@geany.org

alias A(T) = ...;
enum ati1 = is(int == A!int); // OK
enum ati2 = is(int == A!T, T); // can't infer

The second `is` expression should error because DIP1023 is not implemented so the result is always false.

PR incoming.

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