From 2305e6453fbc4360992c34c9fa6be4171cb5b156 Mon Sep 17 00:00:00 2001
From: Chris Mounce <christophermounce@gmail.com>
Date: Sun, 25 May 2025 18:43:36 -0700
Subject: [PATCH] Hacking on grammar! proc macro

- Generated functions take parser state as input
- Start of code generation
- WIP modeling of sequences
---
 Cargo.lock           |  5 +++--
 peg_macro/Cargo.toml |  1 +
 peg_macro/src/lib.rs | 25 +++++++++++++++++++++++--
 src/peg/peg.rs       |  5 +++--
 4 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index aa010b8..efa3af0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -131,6 +131,7 @@ checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 name = "peg_macro"
 version = "0.1.0"
 dependencies = [
+ "proc-macro2",
  "quote",
  "syn",
 ]
@@ -168,9 +169,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.94"
+version = "1.0.95"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a31971752e70b8b2686d7e46ec17fb38dad4051d94024c88df49b667caea9c84"
+checksum = "02b3e5e68a3a1a02aad3ec490a98007cbc13c37cbe84a3cd7b8e406d76e7f778"
 dependencies = [
  "unicode-ident",
 ]
diff --git a/peg_macro/Cargo.toml b/peg_macro/Cargo.toml
index d8360c6..9207d01 100644
--- a/peg_macro/Cargo.toml
+++ b/peg_macro/Cargo.toml
@@ -7,5 +7,6 @@ edition = "2024"
 proc-macro = true
 
 [dependencies]
+proc-macro2 = "1.0.95"
 quote = "1.0.40"
 syn = "2.0.101"
diff --git a/peg_macro/src/lib.rs b/peg_macro/src/lib.rs
index e1fd650..d7c2d14 100644
--- a/peg_macro/src/lib.rs
+++ b/peg_macro/src/lib.rs
@@ -17,8 +17,9 @@ struct Rule {
 }
 
 enum Term {
-    Rule(Ident),
     Literal(LitStr),
+    Rule(Ident),
+    Sequence(Vec<Term>),
 }
 
 impl Parse for Grammar {
@@ -54,6 +55,22 @@ impl Parse for Term {
     }
 }
 
+impl Term {
+    fn generate_code(&self) -> proc_macro2::TokenStream {
+        match self {
+            Term::Rule(ident) => quote! {
+                println!("call subrule");
+                // call subrule
+            },
+            Term::Literal(lit_str) => quote! {
+                println!("parse literal");
+                // call p.literal()
+            },
+            Term::Sequence(terms) => todo!(),
+        }
+    }
+}
+
 #[proc_macro]
 pub fn grammar_old(ts: TokenStream) -> TokenStream {
     let token = ts.into_iter().next().expect("must have at least one token");
@@ -95,12 +112,16 @@ pub fn grammar(ts: TokenStream) -> TokenStream {
                 .map(|t| match t {
                     Term::Rule(ident) => format!("rule {}", ident.to_string()),
                     Term::Literal(lit_str) => format!("literal \"{}\"", lit_str.value()),
+                    Term::Sequence(terms) => todo!(),
                 })
                 .collect();
             let text = format!("I'm generated! ({})", term_strs.join(", "));
 
+            let generated: Vec<_> = r.terms.iter().map(|t| t.generate_code()).collect();
+
             quote! {
-                fn #fn_name() -> String {
+                fn #fn_name(p: &mut crate::peg::ParseState) -> String {
+                    #(#generated)*
                     #text.into()
                 }
             }
diff --git a/src/peg/peg.rs b/src/peg/peg.rs
index d618c51..00bb441 100644
--- a/src/peg/peg.rs
+++ b/src/peg/peg.rs
@@ -85,7 +85,8 @@ mod tests {
 
     #[test]
     fn test_generated() {
-        assert_snapshot!(generated_this(), @"I'm generated! (rule foo)");
-        assert_snapshot!(generated_that(), @r#"I'm generated! (literal "bar", rule baz)"#);
+        let mut p = ParseState::new("");
+        assert_snapshot!(generated_this(&mut p), @"I'm generated! (rule foo)");
+        assert_snapshot!(generated_that(&mut p), @r#"I'm generated! (literal "bar", rule baz)"#);
     }
 }