Okay the proc_macro is actually doing something

At the cost of breaking code

schala-lang/codegen/Cargo.toml

@@ -8,5 +8,5 @@ edition = "2018"
 proc-macro = true
 
 [dependencies]
-syn = { version = "0.15.6", features = ["full", "extra-traits"] }
+syn = { version = "0.15.12", features = ["full", "extra-traits", "fold"] }
 quote = "0.6.8"

schala-lang/codegen/src/lib.rs

@@ -1,11 +1,36 @@
+#![feature(box_patterns)]
 extern crate proc_macro;
 #[macro_use]
 extern crate quote;
+#[macro_use]
 extern crate syn;
 
 use self::proc_macro::TokenStream;
+use self::syn::fold::Fold;
+
+struct RecursiveDescentFn {
+}
+
+impl Fold for RecursiveDescentFn {
+  fn fold_item_fn(&mut self, mut i: syn::ItemFn) -> syn::ItemFn {
+    let box block = i.block;
+    let mut stmts = block.stmts;
+    let new_item: syn::Stmt = parse_quote! {
+      println!("FROM PROC MACRO");
+    };
+    let mut new_stmts = vec![new_item];
+    new_stmts.append(&mut stmts);
+    let new_block = syn::Block { brace_token: block.brace_token, stmts: new_stmts };
+    i.block = Box::new(new_block);
+    i
+  }
+}
 
 #[proc_macro_attribute]
-pub fn parser_function(attr: TokenStream, item: TokenStream) -> TokenStream {
-  item
+pub fn recursive_descent_method(attr: TokenStream, item: TokenStream) -> TokenStream {
+
+  let input: syn::ItemFn = parse_macro_input!(item as syn::ItemFn);
+  let mut folder = RecursiveDescentFn {};
+  let output = folder.fold_item_fn(input);
+  TokenStream::from(quote!(#output))
 }

schala-lang/language/Cargo.toml

@@ -9,5 +9,6 @@ take_mut = "0.1.3"
 maplit = "*"
 lazy_static = "0.2.8"
 
+codegen = { path = "../codegen" }
 schala-repl = { path = "../../schala-repl" }
 schala-repl-codegen = { path = "../../schala-repl-codegen" }

schala-lang/language/src/lib.rs

@@ -1,4 +1,5 @@
 #![feature(trace_macros)]
+#![feature(custom_attribute)]
 #![feature(unrestricted_attribute_tokens)]
 #![feature(slice_patterns, box_patterns, box_syntax)]
 extern crate itertools;
@@ -10,6 +11,8 @@ extern crate maplit;
 extern crate schala_repl;
 #[macro_use]
 extern crate schala_repl_codegen;
+#[macro_use]
+extern crate codegen;
 
 use std::cell::RefCell;
 use std::rc::Rc;

schala-lang/language/src/parsing.rs

@@ -789,7 +789,8 @@ impl Parser {
     })
   });
 
-  parse_method!(signed_number_literal(&mut self) -> ParseResult<Pattern> {
+  #[recursive_descent_method]
+  fn signed_number_literal(&mut self) -> ParseResult<Pattern> {
     let neg = match self.peek() {
       Operator(ref op) if **op == "-" => {
         self.next();
@@ -799,7 +800,7 @@ impl Parser {
     };
     let Expression(expr_type, _) = self.number_literal()?;
     Ok(Pattern::Literal(PatternLiteral::NumPattern { neg, num: expr_type }))
-  });
+  }
 
   parse_method!(record_pattern_entry(&mut self) -> ParseResult<(Rc<String>, Pattern)> {
     let name = self.identifier()?;
@@ -913,12 +914,13 @@ impl Parser {
     }
   });
 
-  parse_method!(number_literal(&mut self) -> ParseResult<Expression> {
+  #[recursive_descent_method]
+  fn number_literal(&mut self) -> ParseResult<Expression> {
     match self.peek() {
       HexLiteral(_) | BinNumberSigil => self.int_literal(),
       _ => self.float_literal(),
     }
-  });
+  }
 
   parse_method!(int_literal(&mut self) -> ParseResult<Expression> {
     use self::ExpressionType::*;