As reported by Paul Sandoz on Valhalla-dev:

The following program fails with a verify error upon running:

public class X {
static final __ByValue class Point {
    final int x;
    final int y;

    Point() {
        x = y = 0; // This is the cause
    }

    static Point point(int x, int y) {
        Point p = __MakeDefault Point();
        p = __WithField(p.x, x);
        p = __WithField(p.y, y);
        return p;
    }

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Point)) return false;
        Point op = (Point) o;

        return x == op.x && y == op.y;
    }

    static Point point() {
        return point(0, 0);
    }
}

public static void main(String[] args) {
  Point p = Point.point();
}
}

Exception in thread "main" java.lang.VerifyError: Bad type on operand stack
Exception Details:
  Location:
    X$Point.$makeValue$()LX$Point; @12: i2b
  Reason:
    Type 'X$Point' (current frame, stack[1]) is not assignable to integer
  Current Frame:
    bci: @12
    flags: { }
    locals: { 'X$Point' }
    stack: { 'X$Point', 'X$Point' }
  Bytecode:
    0000000: cb00 024b 2a2a 03cc 0004 594b 91cc 0003
    0000010: 4b2a b0

at X.main(X.java:31)

The culprit seems to be the chained assignment
    x = y = 0; // This is the cause

If it was broken down into two statement, things are fine.