associated function build is private

[SOF3]

Problem

HTML macro fails with the error associated function build is private.

error[E0624]: associated function `build` is private
   --> /home/sofe/.cargo/registry/src/github.com-1ecc6299db9ec823/yew-0.17.4/src/lib.rs:101:1
    |
101 |       #[proc_macro_hack(support_nested)]
    |       ^---------------------------------
    |       |
    |       in this expansion of `html!` (#1)
    |  _____in this macro invocation (#2)
    | |_____|
    | |
102 | |     pub use yew_macro::html;
    | |                           ^
    | |___________________________|
    | |___________________________private associated function
    |                             in this expansion of `proc_macro_call_0!` (#6)
    | 
   ::: /home/sofe/.cargo/registry/src/github.com-1ecc6299db9ec823/proc-macro-nested-0.1.6/src/lib.rs:47:1
    |
47  |       macro_rules! dispatch {
    |  _____-
    | |_____|
    | |_____|
    | |
48  | |         (() $($bang:tt)*) => {
49  | |             $crate::count!($($bang)*)
    | |             ------------------------- in this macro invocation (#5)
50  | |         };
...   |
67  | |             $crate::dispatch!(($($rest)*) $($bang)*)
    | |             ----------------------------------------
    | |             |
    | |             in this macro invocation (#3)
    | |             in this macro invocation (#4)
68  | |         };
69  | |     }
    | |     -
    | |_____|
    | |_____in this expansion of `$crate::proc_macro_call_html!` (#2)
    | |_____in this expansion of `$crate::dispatch!` (#3)
    |       in this expansion of `$crate::dispatch!` (#4)
    | 
   ::: /home/sofe/proj/traffloat/target/debug/build/proc-macro-nested-54f78155b0ce2171/out/count.rs:3:1
    |
3   |     / macro_rules! count {
4   |     |     () => { proc_macro_call_0!() };
    |     |             -------------------- in this macro invocation (#6)
5   |     |     (!) => { proc_macro_call_1!() };
6   |     |     (!!) => { proc_macro_call_2!() };
...       |
71  |     |     };
72  |     | }
    |     |_- in this expansion of `$crate::count!` (#5)
    | 
   ::: client/src/app/mod.rs:32:28
    |
32  |                   State::Menu => html! {
    |  ________________________________-
33  | |                     <menu::Menu />
34  | |                 }
    | |_________________- in this macro invocation (#1)

Steps To Reproduce

I import use yew::prelude::*; with a submodule mod menu; with the code

            html! {
                <menu::Menu />
            }

with the Properties definition for Menu:

#[derive(Clone, Properties)]
struct Properties {
    #[prop_or("localhost".to_string())]
    address: String,
    #[prop_or(common::DEFAULT_PORT)]
    port: u16,
}

I cannot find this error anywhere, so I suppose I'm running into a corner case.

Environment:

• Yew version: 0.17.4
• Rust version: 1.49.0
• Target, if relevant: cargo check on linux already fails
• Build tool, if relevant: cargo check already fails
• Web library: web-sys
• OS, if relevant: ubuntu 20

Questionnaire

• I'm interested in fixing this myself but don't know where to start
• I would like to fix and I have a solution
• I don't have time to fix this right now, but maybe later

[SOF3]

cargo-expand gives

                    #[allow(dead_code)]
                    enum ProcMacroHack {
                        Nested = ("< menu :: Menu / >", 0).1,
                    }
                    ::yew::virtual_dom::VNode::from({
                        if false {}
                        :: yew :: virtual_dom :: VChild :: < menu :: Menu > :: new (< < menu :: Menu as :: yew :: html :: Component > :: Properties as :: yew :: html :: Properties > :: builder () . build () , :: yew :: html :: NodeRef :: default () , None)
                    })

[SOF3]

cargo-expand also shows

    impl PropertiesBuilder<PropertiesBuilderStep_build> {
        #[doc(hidden)]
        fn build(self) -> Properties {
            Properties {}
        }
    }
    impl ::yew::html::Properties for Properties {
        type Builder = PropertiesBuilder<PropertiesBuilderStep_build>;
        fn builder() -> Self::Builder {
            PropertiesBuilder {
                wrapped: ::std::boxed::Box::new(::std::default::Default::default()),
                _marker: ::std::marker::PhantomData,
            }
        }
    }

for the properties.
It appears that Properties::Builder::build() is declared as a fn build(self) without public visibility.
This is probably because my struct Properties is private.

But it is actually not necessary to make my struct Properties public, because it is only used as an associated type in the impl Component for Menu in the same module.

Should I send a PR that makes the build() function always pub?

[SOF3]

Never mind, this actually leads to E0446 even if the builder works.

[jstarry]

Ah yeah, appears that the properties magic only works with public properties types? Sorry you bumped into this