https://issues.dlang.org/show_bug.cgi?id=20429

          Issue ID: 20429
           Summary: extern(C++) mangling of multiple const ref params
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: john.loughran.colvin@gmail.com

extern(C++, blah):

struct S {}

void foo(ref const(S) s0, ref const(S) s1);
pragma(msg, foo.mangleof);
void bar(ref const(S) s0, const(S) s1);
pragma(msg, foo.mangleof);

The foo and bar are mangled the same, and in both s1 is not mangled as ref, but s0  is.

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