commit d09e012608fbe9c0e6929e33ae5f8dc214fbb1d1
author David Tolnay <dtolnay@gmail.com> Mon May 04 02:34:23 2020 -0700
committer David Tolnay <dtolnay@gmail.com> Thu May 07 19:46:01 2020 -0700
tree 442fc715690a0dc8c5592b831f9f577fe153218a
parent db08d4affec5fa375736e7652ebe54c253bc29e1

Add a type-level encoding of qualified paths

macro/src/lib.rs

diff --git a/macro/src/lib.rs b/macro/src/lib.rs
index b56f58e..bc8d19b 100644
--- a/macro/src/lib.rs
+++ b/macro/src/lib.rs
@@ -11,10 +11,11 @@
 
 mod expand;
 mod syntax;
+mod type_id;
 
 use crate::syntax::namespace::Namespace;
 use proc_macro::TokenStream;
-use syn::{parse_macro_input, ItemMod};
+use syn::{parse_macro_input, ItemMod, LitStr};
 
 /// `#[cxx::bridge] mod ffi { ... }`
 ///
@@ -44,3 +45,9 @@
         .unwrap_or_else(|err| err.to_compile_error())
         .into()
 }
+
+#[proc_macro]
+pub fn type_id(input: TokenStream) -> TokenStream {
+    let arg = parse_macro_input!(input as LitStr);
+    type_id::expand(arg).into()
+}

macro/src/type_id.rs

diff --git a/macro/src/type_id.rs b/macro/src/type_id.rs
new file mode 100644
index 0000000..15a5833
--- /dev/null
+++ b/macro/src/type_id.rs
@@ -0,0 +1,29 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use syn::LitStr;
+
+// "folly::File" => `(f, o, l, l, y, (), F, i, l, e)`
+pub fn expand(arg: LitStr) -> TokenStream {
+    let mut ids = Vec::new();
+
+    for word in arg.value().split("::") {
+        if !ids.is_empty() {
+            ids.push(quote!(()));
+        }
+        for ch in word.chars() {
+            ids.push(match ch {
+                'A'..='Z' | 'a'..='z' => {
+                    let t = format_ident!("{}", ch);
+                    quote!(::cxx::private::#t)
+                }
+                '0'..='9' | '_' => {
+                    let t = format_ident!("_{}", ch);
+                    quote!(::cxx::private::#t)
+                }
+                _ => quote!([(); #ch as _]),
+            });
+        }
+    }
+
+    quote! { (#(#ids,)*) }
+}

src/lib.rs

diff --git a/src/lib.rs b/src/lib.rs
index cc0dcf2..39b1ecc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -376,6 +376,7 @@
 mod rust_str;
 mod rust_string;
 mod rust_vec;
+mod type_id;
 mod unique_ptr;
 mod unwind;
 
@@ -386,7 +387,7 @@
 pub use crate::cxx_vector::CxxVector;
 pub use crate::exception::Exception;
 pub use crate::unique_ptr::UniquePtr;
-pub use cxxbridge_macro::bridge;
+pub use cxxbridge_macro::{bridge, type_id};
 
 // Not public API.
 #[doc(hidden)]
@@ -399,6 +400,7 @@
     pub use crate::rust_str::RustStr;
     pub use crate::rust_string::RustString;
     pub use crate::rust_vec::RustVec;
+    pub use crate::type_id::*;
     pub use crate::unique_ptr::UniquePtrTarget;
     pub use crate::unwind::catch_unwind;
 }

src/type_id.rs

diff --git a/src/type_id.rs b/src/type_id.rs
new file mode 100644
index 0000000..68020ea
--- /dev/null
+++ b/src/type_id.rs
@@ -0,0 +1,16 @@
+#![allow(non_camel_case_types)]
+
+macro_rules! chars {
+    ($($ch:ident)*) => {
+        $(
+            pub enum $ch {}
+        )*
+    };
+}
+
+chars! {
+    _0 _1 _2 _3 _4 _5 _6 _7 _8 _9
+    A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
+    a b c d e f g h i j k l m n o p q r s t u v w x y z
+    __ // underscore
+}