Custom lexers can now terminate operators

New constraint: custom lexer output is dropped whenever it is used to terminate an operator nested inside another custom lexer, because the recursive call has to return exactly one lexeme

orcx/src/main.rs

@@ -205,8 +205,14 @@ async fn main() -> io::Result<ExitCode> {
 					let mut file = File::open(file.as_std_path()).unwrap();
 					let mut buf = String::new();
 					file.read_to_string(&mut buf).unwrap();
-					let lexemes = lex(is(&buf).await, sym!(usercode), &systems, ctx).await.unwrap();
-					println!("{}", take_first(&ttv_fmt(&lexemes, &FmtCtxImpl::default()).await, true))
+					match lex(is(&buf).await, sym!(usercode), &systems, ctx).await {
+						Ok(lexemes) =>
+							println!("{}", take_first(&ttv_fmt(&lexemes, &FmtCtxImpl::default()).await, true)),
+						Err(e) => {
+							eprintln!("{e}");
+							exit_code1.replace(ExitCode::FAILURE);
+						},
+					}
 				},
 				Commands::Parse { file } => {
 					let (_, systems) = init_systems(&args.system, &extensions).await.unwrap();
@@ -472,6 +478,7 @@ async fn main() -> io::Result<ExitCode> {
 		for (rc, expr) in &exprs {
 			eprintln!("{rc}x {:?} = {}", expr.id(), fmt(expr).await)
 		}
+		std::process::abort()
 	};
 	futures::future::select(
 		pin!(cleanup),