[AA] unable to compare const associative array with mutable

[dlangBugzillaToGithub]

Igor Stepanov reported this on 2014-10-16T21:54:24Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=13622

Description

void main() 
{
    int[int] aa1 = [1:2];
    const int[int] aa2 = aa1;
    assert(aa1 == aa2);
}

This code causes a error: 
Error: incompatible types for ((aa1) == (aa2)): 'int[int]' and 'const(int[int])'