[Issue 20919] New: DMD crash when '__traits' prints error involving a Parameter

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20919

          Issue ID: 20919
           Summary: DMD crash when '__traits' prints error involving a
                    Parameter
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: boris2.9 at gmail.com

test:
----------------------------
void foo(int a){}

static if (is(typeof(foo) params == __parameters))
{
    __traits(getAttributes, params) a;
}
----------------------------

Patch ready.

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