lang: replace stack-based parser with a recursive parser

lang/parse/match.c

@@ -0,0 +1,75 @@
+#include "ctx.h"
+
+#include <ivy/lang/ast.h>
+
+bool parse_match(struct ivy_parser *parser, struct ivy_ast_node **out)
+{
+	if (!parse_keyword(parser, IVY_KW_MATCH)) {
+		parse_trace(parser, "expected `match` keyword");
+		return false;
+	}
+
+	struct ivy_ast_match_node *match = create_node(IVY_AST_MATCH);
+
+	if (!parse_expr(parser, EXPR_PARSE_STOP_LEFT_BRACKET, &match->n_cond)) {
+		parse_trace(parser, "invalid match predicate");
+		return false;
+	}
+
+	if (!parse_symbol(parser, IVY_SYM_LEFT_BRACKET)) {
+		parse_trace(parser, "expected `[` after match predicate");
+		return false;
+	}
+
+	bool ok = true;
+	while (1) {
+		if (parse_symbol(parser, IVY_SYM_RIGHT_BRACKET)) {
+			break;
+		}
+
+		if (!fx_queue_empty(&match->n_branches)
+		    && !parse_symbol(parser, IVY_SYM_COMMA)) {
+			parse_trace(
+				parser,
+				"expected `,` or `]` after match branch value");
+			ok = false;
+			break;
+		}
+
+		struct ivy_ast_node *branch_pred = NULL;
+		struct ivy_ast_node *branch_value = NULL;
+		if (!parse_expr(parser, EXPR_PARSE_NORMAL, &branch_pred)) {
+			parse_trace(parser, "invalid match branch predicate");
+			ok = false;
+			break;
+		}
+
+		if (!parse_symbol(parser, IVY_SYM_EQUAL_RIGHT_ANGLE)) {
+			parse_trace(
+				parser,
+				"expected `=>` after match branch predicate");
+			ok = false;
+			break;
+		}
+
+		if (peek_symbol(parser, IVY_SYM_LEFT_BRACKET)) {
+			ok = parse_block(parser, &branch_value);
+		} else {
+			ok = parse_expr(
+				parser, EXPR_PARSE_STOP_COMMA, &branch_value);
+		}
+
+		if (!ok) {
+			parse_trace(parser, "invalid match branch value");
+			break;
+		}
+
+		struct ivy_ast_cond_node *cond = create_node(IVY_AST_COND);
+		cond->n_cond = branch_pred;
+		cond->n_body = branch_value;
+		fx_queue_push_back(&match->n_branches, &cond->n_base.n_entry);
+	}
+
+	*out = generic_node(match);
+	return true;
+}