add simple ast dimension diagnostic

Signed-off-by: Jason Volk <jason@zemos.net>

src/macros/debug.rs

@@ -0,0 +1,28 @@
+use std::cmp;
+
+use proc_macro::TokenStream;
+use syn::{parse_macro_input, AttributeArgs, Item};
+
+pub(super) fn recursion_depth(args: TokenStream, item_: TokenStream) -> TokenStream {
+	let item = item_.clone();
+	let item = parse_macro_input!(item as Item);
+	let _args = parse_macro_input!(args as AttributeArgs);
+
+	let mut best: usize = 0;
+	let mut count: usize = 0;
+	// think you'd find a fancy recursive ast visitor? think again
+	let tree = format!("{item:#?}");
+	for line in tree.lines() {
+		let trim = line.trim_start_matches(' ');
+		let diff = line.len().saturating_sub(trim.len());
+		let level = diff / 4;
+		best = cmp::max(level, best);
+		count = count.saturating_add(1);
+	}
+
+	println!("--- Recursion Diagnostic ---");
+	println!("DEPTH: {best}");
+	println!("LENGTH: {count}");
+
+	item_
+}