Interesting... this small program causes DMD to crash:

import intrinsic;

public:

// VECTOR

alias float[2] vector2;

float lengthsquared(vector2 a)
{
  return a[0]*a[0]+a[1]*a[1];
}

float length(vector2 a)
{
  return sqrt(lengthsquared(a));
}

unittest
{
  float n;
 vector2 a,b,c;
 a[0]=0; a[1]=1;
 b[0]=1; b[1]=0;
 //c[] = a[] + b[];
 //c = a - b;
 //c = a * b;
 //c = a / b;
 n = lengthsquared(a);
 n = length(a);
}

// POINT

typedef vector2 point2;

// POINT TO POINT DISTANCE

float distance(point2 a, point2 b)
{
  point2 d;
  d[0] = b[0] - a[0];
  d[1] = b[1] - a[1];
  return length(d);
}

unittest
{
    float d;
    point2 a,b;
   a[0]=0; a[1]=1;
   b[0]=1; b[1]=0;
    d = distance(a,b);
}