[steveklabnik]

Regular variable definition shadows. Macros expand to regular Rust code, they could always be replaced by the expanded body.

[kobebrookskC3]

yes, but the code inside is unsafe. the pin macro is like a safe function.

[steveklabnik]

I'm not sure what that has to do with anything. The macro isn't what makes it safe. The unsafe code being properly written is.

[kobebrookskC3]

but without macros, how would you expose a safe interface?

  fn pin(x: T) -> Pin<&mut T> { ... }

would move the value

[Philpax]

Your macroless variant of Rust would offer a safe builtin that does this. It doesn't need to be implemented with a macro.