[derive] Start to move manually_traced macros over to proc_derive

Procedural macros are more flexible and will allow us to use a
single macro for all our manually traced code.
It should also help downstream crates start to utilize this.

Author: Techcable

Cargo.toml

@@ -13,6 +13,8 @@ readme = "README.md"
 # Providing support for these important libraries,
 # gives zerogc 'batteries included' support.
 indexmap = { version = "1.6", optional = true }
+# Used for macros
+zerogc-derive = { version = "0.2.0-alpha.1" }
 
 [workspace]
 members = ["libs/simple", "libs/derive", "libs/context"]

libs/derive/Cargo.toml

@@ -16,6 +16,6 @@ zerogc = { version = "0.2.0-alpha.1", path = "../.." }
 
 [dependencies]
 # Proc macros
-syn = "1.0.55"
+syn = { version = "1.0.55", features = ["full", "extra-traits"] }
 quote = "1.0.8"
 proc-macro2 = "1"

libs/derive/src/lib.rs

@@ -12,6 +12,8 @@ use std::collections::HashSet;
 use std::fmt::Display;
 use std::io::Write;
 
+mod macros;
+
 struct MutableFieldOpts {
     public: bool
 }
@@ -334,6 +336,22 @@ impl Parse for TypeAttrs {
     }
 }
 
+#[proc_macro]
+pub fn unsafe_gc_impl(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let cloned_impl = input.clone();
+    let parsed = parse_macro_input!(input as macros::MacroInput);
+    let res = parsed.expand_output()
+        .unwrap_or_else(|e| e.to_compile_error());
+    debug_derive(
+        "unsafe_gc_impl!",
+        &"",
+        &format_args!("#[unsafe_gc_impl {{ {} }}", cloned_impl),
+        &res
+    );
+    res.into()
+}
+
+
 #[proc_macro_derive(Trace, attributes(zerogc))]
 pub fn derive_trace(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
     let input = parse_macro_input!(input as DeriveInput);