lang: implement elif keyword for more complex if-statements

lang/ast/block.c

@@ -160,6 +160,7 @@ struct ast_node_type block_node_ops = {
 		KW_PARSER(VAR, parse_var),
 		KW_PARSER(END, parse_end),
 		KW_PARSER(ELSE, parse_else),
+		KW_PARSER(ELIF, parse_else), /* same behaviour as ELSE */
 		KW_PARSER_FALLBACK(parse_keyword),
 	},
 	.n_symbol_parsers = {

lang/ast/cond.c

@@ -20,6 +20,24 @@ static void init_state(struct ivy_parser *ctx, struct parser_state *sp, uintptr_
 	state->s_prev_node = (struct ivy_ast_node *)arg;
 }
 
+static enum ivy_status flush_current_branch(struct cond_group_parser_state *state)
+{
+	if (!state->s_cur_branch) {
+		return IVY_ERR_INTERNAL_FAILURE;
+	}
+
+	b_queue_push_back(&state->s_branches, &state->s_cur_branch->n_base.n_entry);
+
+	state->s_cur_branch
+		= (struct ivy_ast_cond_node *)ast_node_create(IVY_AST_COND);
+
+	if (!state->s_cur_branch) {
+		return IVY_ERR_NO_MEMORY;
+	}
+
+	return IVY_OK;
+}
+
 struct token_parse_result parse_if(struct ivy_parser *ctx, struct ivy_token *tok)
 {
 	struct cond_group_parser_state *state
@@ -54,22 +72,45 @@ struct token_parse_result parse_if(struct ivy_parser *ctx, struct ivy_token *tok
 	return PARSE_RESULT(IVY_OK, 0);
 }
 
-static enum ivy_status flush_current_branch(struct cond_group_parser_state *state)
+struct token_parse_result parse_elif(struct ivy_parser *ctx, struct ivy_token *tok)
 {
+	struct cond_group_parser_state *state
+		= parser_get_state(ctx, struct cond_group_parser_state);
+
 	if (!state->s_cur_branch) {
-		return IVY_ERR_INTERNAL_FAILURE;
+		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
 	}
 
-	b_queue_push_back(&state->s_branches, &state->s_cur_branch->n_base.n_entry);
+	if (state->s_inline) {
+		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
+	}
+
+	if (state->s_prev_token != IVY_KW_THEN) {
+		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
+	}
+
+	state->s_cur_branch->n_body = state->s_prev_node;
+	state->s_prev_node = NULL;
+
+	enum ivy_status status = flush_current_branch(state);
+	if (status != IVY_OK) {
+		return PARSE_RESULT(status, 0);
+	}
 
 	state->s_cur_branch
 		= (struct ivy_ast_cond_node *)ast_node_create(IVY_AST_COND);
-
 	if (!state->s_cur_branch) {
-		return IVY_ERR_NO_MEMORY;
+		return PARSE_RESULT(IVY_ERR_NO_MEMORY, 0);
 	}
 
-	return IVY_OK;
+	struct expr_parser_state *expr
+		= (struct expr_parser_state *)parser_push_state(
+			ctx, IVY_AST_EXPR, 0);
+
+	state->s_prev_token = IVY_KW_ELIF;
+	expr->s_subexpr_depth = 1;
+
+	return PARSE_RESULT(IVY_OK, 0);
 }
 
 static struct token_parse_result parse_then(
@@ -86,7 +127,7 @@ static struct token_parse_result parse_then(
 		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
 	}
 
-	if (state->s_prev_token != IVY_KW_IF) {
+	if (state->s_prev_token != IVY_KW_IF && state->s_prev_token != IVY_KW_ELIF) {
 		return PARSE_RESULT(IVY_ERR_BAD_SYNTAX, 0);
 	}
 
@@ -103,6 +144,8 @@ static struct token_parse_result parse_then(
 		= (struct block_parser_state *)parser_push_state(
 			ctx, IVY_AST_BLOCK, 0);
 	/* set the sub-expression depth to be non-zero so the expression parser doesn't consume the expression separator. */
+	block_add_terminator(block, IVY_KW_ELIF);
+	block_add_terminator(block, IVY_KW_ELSE);
 	block_add_terminator(block, IVY_KW_END);
 
 	state->s_prev_token = IVY_KW_THEN;
@@ -138,7 +181,7 @@ static struct token_parse_result parse_else(
 			return PARSE_RESULT(status, 0);
 		}
 
-		/* next component should either be an if keyword or a block. */
+		/* next component should be a block. */
 	} else {
 		/* previous component was the if-condition. */
 		if (!state->s_prev_node) {
@@ -332,6 +375,7 @@ struct ast_node_type cond_group_node_ops = {
 	.n_keyword_parsers = {
 		KW_PARSER(IF, parse_if),
 		KW_PARSER(THEN, parse_then),
+		KW_PARSER(ELIF, parse_elif),
 		KW_PARSER(ELSE, parse_else),
 		KW_PARSER(END, parse_end),
 	},

lang/ast/expr/expr.c

@@ -84,6 +84,7 @@ struct ast_node_type expr_node_ops = {
 		KW_PARSER(IF, stmt_parse_if),
 		KW_PARSER(THEN, stmt_parse_end),
 		KW_PARSER(ELSE, stmt_parse_end),
+		KW_PARSER(ELIF, stmt_parse_end),
 		KW_PARSER(CATCH, stmt_parse_end),
 		KW_PARSER(FINALLY, stmt_parse_end),
 		KW_PARSER(END, stmt_parse_end),