start slotted-egraphs-derive

Cargo.toml

@@ -15,6 +15,7 @@ trace = ["tracing/max_level_trace", "tracing/release_max_level_trace", "tracing"
 features = ["explanations"]
 
 [dependencies]
+slotted-egraphs-derive = { path = "slotted-egraphs-derive" }
 fnv = "1.0.7"
 tracing = { version = "0.1", features = ["attributes"], optional = true }
 

slotted-egraphs-derive/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "slotted-egraphs-derive"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+syn = { version = "2.0", features = ["full"] }
+quote = "1.0"
+proc-macro2 = "1.0"
+
+[lib]
+proc-macro = true

slotted-egraphs-derive/src/lib.rs

@@ -0,0 +1,14 @@
+use proc_macro::TokenStream as TokenStream1;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::{format_ident, quote, ToTokens};
+use syn::*;
+
+#[proc_macro]
+pub fn define_language(input: TokenStream1) -> TokenStream1 {
+    let mut xx: ItemEnum = parse(input).unwrap();
+    xx.variants.iter_mut().for_each(|x| {
+        x.attrs.clear();
+        x.discriminant = None;
+    });
+    quote! { #xx }.to_token_stream().into()
+}

src/lang.rs

@@ -1,5 +1,19 @@
 use crate::*;
 
+pub struct Bind<T> {
+    pub slot: Slot,
+    pub elem: T,
+}
+
+define_language! {
+    enum ExampleLanguage {
+        Lambda(Bind<AppliedId>) = "lambda",
+        App(AppliedId, AppliedId) = "app",
+        Var(Slot) = "var",
+        #[substitution_op] Let(AppliedId, Bind<AppliedId>) = "let",
+    }
+}
+
 #[derive(Debug, Clone)]
 /// A child node of some term ("child" in the sense of an AST).
 ///

src/lib.rs

@@ -26,6 +26,8 @@ const CHECKS: bool = true;
 #[cfg(not(feature = "checks"))]
 const CHECKS: bool = false;
 
+pub use slotted_egraphs_derive::define_language;
+
 mod slot;
 pub use slot::*;