`decl_macro` can call `pub fn` methods of private types.

[theemathas]

I tried this code:

#![feature(decl_macro)]
macro my_macro($val:expr) {
    $val.method()
}

pub mod module {
    struct Thing;
    impl Thing {
        pub fn method(&self) -> bool {
            true
        }
    }
    pub fn weird() -> bool {
        super::my_macro!(Thing)
    }
}

The method is a pub fn. However, it is implemented on a private type. Therefore, it should not be callable from outside the module. So, this code shouldn't compile. Instead, this code compiles without errors.

Changing pub fn method to fn method causes the following error, as expected:

error[E0624]: method `method` is private
  --> src/lib.rs:3:10
   |
 3 |     $val.method()
   |          ^^^^^^ private method
...
 9 |         fn method(&self) -> bool {
   |         ------------------------ private method defined here
...
14 |         super::my_macro!(Thing)
   |         ----------------------- in this macro invocation
   |
   = note: this error originates in the macro `super::my_macro` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0624`.

This behavior also seems to apply to built-in macros. See #155598 (comment)

Meta

Reproducible on the playground with 1.97.0-nightly (2026-04-20 66da6cae1a6f12e95854)

[juntyr]

Isn't the macro invoked only in the weird function, where Thing is visible? Or should that only be allowed with a macro-rules macro?

[theemathas]

@juntyr If that's the case, then there's a different bug: The code doesn't compile when the method isn't pub, for some reason.

[bjorn3]

decl_macro uses def-site hygiene, which means that only methods visible from the macro definition site can be called. Thing can be used just fine despite being private as it is explicitly passed to the macro, which gives it call-site hygiene.