Typescript doesn't have semantics on its own. It's a syntax for JavaScript with a static type checker on top. A lot of JavaScript isn't really suitable for a low level language because of GC, heavy use of very flexible objects, any, only a number type instead of int8/16/... and float32/64, ...
Assemblyscript is essentially a very restricted, low level variant of TS.
If you really want JavaScript in WASM, you can already get that by using Spidermonkey compiled to WASM as an interpreter. A compiled version of TS could be interesting, but would be a lot of work and would come with a lot of difficult challenges for getting could performance.
I will say though that I'd much rather use Rust than AS though, so I do see how the language has limited appeal.
Assemblyscript is essentially a very restricted, low level variant of TS.
If you really want JavaScript in WASM, you can already get that by using Spidermonkey compiled to WASM as an interpreter. A compiled version of TS could be interesting, but would be a lot of work and would come with a lot of difficult challenges for getting could performance.
I will say though that I'd much rather use Rust than AS though, so I do see how the language has limited appeal.