Compile serde_derive to wasm

serde_derive/Cargo.toml

@@ -17,8 +17,7 @@ default = []
 deserialize_in_place = []
 
 [lib]
-name = "serde_derive"
-proc-macro = true
+crate-type = ["cdylib"]
 
 [dependencies]
 proc-macro2 = "1.0"
@@ -30,3 +29,8 @@ serde = { version = "1.0", path = "../serde" }
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]
+
+[workspace]
+
+[patch.crates-io]
+proc-macro2 = { git = "https://github.com/dtolnay/watt" }

serde_derive/src/lib.rs

@@ -68,12 +68,11 @@ extern crate quote;
 #[macro_use]
 extern crate syn;
 
-extern crate proc_macro;
 extern crate proc_macro2;
 
 mod internals;
 
-use proc_macro::TokenStream;
+use proc_macro2::TokenStream;
 use syn::DeriveInput;
 
 #[macro_use]
@@ -87,23 +86,27 @@ mod pretend;
 mod ser;
 mod try;
 
-#[proc_macro_derive(Serialize, attributes(serde))]
-pub fn derive_serialize(input: TokenStream) -> TokenStream {
-    let mut input = parse_macro_input!(input as DeriveInput);
-    ser::expand_derive_serialize(&mut input)
-        .unwrap_or_else(to_compile_errors)
-        .into()
+#[no_mangle]
+pub extern "C" fn derive_serialize(input: TokenStream) -> TokenStream {
+    let mut input: DeriveInput = match syn::parse2(input) {
+        Ok(input) => input,
+        Err(err) => return err.to_compile_error(),
+    };
+
+    ser::expand_derive_serialize(&mut input).unwrap_or_else(to_compile_errors)
 }
 
-#[proc_macro_derive(Deserialize, attributes(serde))]
-pub fn derive_deserialize(input: TokenStream) -> TokenStream {
-    let mut input = parse_macro_input!(input as DeriveInput);
-    de::expand_derive_deserialize(&mut input)
-        .unwrap_or_else(to_compile_errors)
-        .into()
+#[no_mangle]
+pub extern "C" fn derive_deserialize(input: TokenStream) -> TokenStream {
+    let mut input: DeriveInput = match syn::parse2(input) {
+        Ok(input) => input,
+        Err(err) => return err.to_compile_error(),
+    };
+
+    de::expand_derive_deserialize(&mut input).unwrap_or_else(to_compile_errors)
 }
 
-fn to_compile_errors(errors: Vec<syn::Error>) -> proc_macro2::TokenStream {
+fn to_compile_errors(errors: Vec<syn::Error>) -> TokenStream {
     let compile_errors = errors.iter().map(syn::Error::to_compile_error);
     quote!(#(#compile_errors)*)
 }