chromium/third_party/blink/web_tests/svg/custom/rect-calc-corner-radii.svg

<svg xmlns="http://www.w3.org/2000/svg" width="500" height="500">
    <rect  x="50" y="50"  width="400" height="400" rx="calc(-50)"  ry="calc(-50)"  fill="#00ff00" />
    <rect x="150" y="100" width="200" height="300" rx="calc(20% - 50px)" ry="50" fill="#0000ff" />
    <rect x="200" y="150" width="100" height="200" rx="50" ry="-100" fill="#ff0000" />
</svg>