[delta_p_delta_x]

> Types don't carry behavioral information about what the method does internally.

I was under the impression type inference meant that the implementation of a function directly determines the return type of a function, and therefore its signature and type.

[jhugo]

While you can sometimes elide the return type (and what you describe only happens in closures — `|| { 0u32 }` is the same as `|| -> u32 { 0u32 }` — methods and free functions must always have an explicitly declared return type), that's not the same thing as being described above.

For the existence of any invocation of `<T as Clone>::clone()` in the method body to be encoded in the method signature, we'd either need some wild new syntax, or the compiler would need to be able to encode hidden information into types beyond what is visible to the programmer, which would make it very hard to reason about its behavior.

[mryall]

No, Rust functions have to declare their return types. They cannot be inferred.