[jfbastien]

Except with all browser vendors being involved with WebAssembly, efficient polyfill-ability hasn't been a goal for a while.

[cromwellian]

WASM has 64-bit ints, did asm.js support those? How can you polyfill that without a real slowdown.

[recursive]

A property with getter and setter backed by singleton typed array instance?

[cromwellian]

"without a real slowdown"

Any operation, like 64-bit adds/muls/divs/etc would have to call emulation functions. It'll be orders of magnitude slower.