[flohofwoe]

> but I don’t understand how #2 cross-lang interop could ever have been optional

This problem hasn't been solved outside the web either (at least not to the satisfaction of Rust fanboys who expect that they can tunnel their high level stdlib types directly to other languages - while conveniently ignoring that other languages have completely different semantics and very little overlap with the Rust stdlib).

At the core, the component model is basically an attempt to tunnel high level types to other languages, but with a strictly Rust-centric view of the world (the selection of 'primitive types' is essentially a random collection of Rust stdlib types).

[jnbridge]

The cross-language type-mapping problem is where every interop approach eventually runs aground. The component model's challenge is the same one that hit every bridge technology before it: whose type system is "canonical"?

.NET's Common Type System was supposed to be the neutral ground for dozens of languages. In practice, it had strong C# biases — try using unsigned integers from VB or F#'s discriminated unions from C#. The CLR "primitive types" were just as much a random collection as the WIT primitives are being described here.

The practical lesson from two decades of cross-runtime integration: stop trying to tunnel high-level types. The approaches that survive in production define a minimal shared surface (essentially: scalars, byte buffers, and handles) and let each side do its own marshaling. It's less elegant but it doesn't break every time one side's stdlib evolves.

WASM's linear memory model actually gets this right at the low level — the problem is everyone wants the convenience layer on top, and that's where the type-system politics start.

[pjmlp]

Except you are missing the part that CLR has a type system designed specifically for cross language interop, and is taken into account on the design of WinRT as well.

Common Language Specification - https://simple.wikipedia.org/wiki/Common_Language_Specificat...

> The CLS was designed to be large enough to include the language constructs that are commonly needed by developers, yet small enough that most languages are able to support it. Any language construct that makes it impossible to quickly confirm the type safety of code was excluded from the CLS so that all languages that can work with CLS can produce verifiable code if they choose to do so.

WinRT Type System - https://learn.microsoft.com/en-us/uwp/winrt-cref/winrt-type-...

[laughinghan]

The WIT types don’t seem random or Rust-centric to me, they’re basic types common to every major current-generation language, not just Rust but also Swift, Kotlin, even Zig. It’s true that languages with type designs from the 90s can’t take full advantage of WIT types, but WIT does seem perfectly capable of representing types from older languages, which seems like the only possible sensible design to me—older languages are supported, but that support needn’t burden interop between modern languages.