From the test suite, test1() in testtypeid.d, if 'typedef' is replaced by 'alias', a runtime segfault occurs. It works if typedef is used instead.

import std.stdio;

class ABC { }

alias ABC DEF; // typedef ABC DEF; is OK.

TypeInfo foo()
{
    ABC c;

    return typeid(DEF);
}

void main()
{
    TypeInfo ti = foo();
    TypeInfo_Typedef td = cast(TypeInfo_Typedef)ti;
    assert(td);

    ti = td.base;

    TypeInfo_Class tc = cast(TypeInfo_Class)ti;
    assert(tc);

    printf("%.*s\n", tc.info.name.length, tc.info.name.ptr);
    assert(tc.info.name == "testtypeid.ABC");
    
}