lang: first test and stuff

crates/lang/src/parser/grammar.rs

@@ -1,6 +1,13 @@
+use std::fmt::Debug;
+
 use crate::parser::syntax_kind::SyntaxKind::*;
 
-use super::Parser;
+use super::{
+    input::Input,
+    output::Output,
+    syntax_kind::{self, lex},
+    Parser,
+};
 
 mod expression;
 
@@ -12,3 +19,16 @@ pub fn source_file(p: &mut Parser) {
 
     root.complete(p, ROOT);
 }
+
+fn check_parser(input: &str, parser_fn: fn(&mut Parser), output: &str) {
+    let toks = lex(input);
+    let mut parser = Parser::new(Input::new(&toks));
+
+    parser_fn(&mut parser);
+
+    let p_out = dbg!(parser.finish());
+    let o = Output::from_parser_output(toks, p_out);
+
+    let s = format!("{o:?}");
+    assert_eq!(&s, output);
+}