Wasm compilation of int

[lukehutch]

When compiling Dart to wasm, numeric types are compiled as JSNumber:

https://dart.dev/interop/js-interop/js-types

However, wasm has two different native types 64-bit numerical types, i64 and f64:

https://webassembly.github.io/gc/core/syntax/types.html

When Dart is compiled to native code, int is compiled as a 64-bit int, rather than a Javascript-compatible 52-bit integer type packed into a number.

Why does Dart not compile int to i64 on wasm? In other words, why is there not a WASMi64 type and a WASMf64 type, rather than just JSNumber?

[dart-github-bot]

Summary: Dart's Wasm compilation uses JSNumber for int, unlike native compilation which uses 64-bit ints. The user requests i64 and f64 Wasm types instead.

[mraleph]

When compiling Dart to wasm, numeric types are compiled as JSNumber:

That's not true. When compiling Dart to Wasm numerics are represented in the same way as on native runtime: unboxed int and double are represented as i64 and f64 values respectively.

JSNumber represents a JS number - like its name indicates.