From e927a4b22115e0461db6feeee891256b10650c0e Mon Sep 17 00:00:00 2001
From: Johnny Richard <johnny@johnnyrichard.com>
Date: Fri, 14 Apr 2023 23:10:25 +0200
Subject: parser: Create parser for function with return statements

This is a very limited parser implementation which parses a single
function with return type i32 and body containing a return number statement.

The parser doesn't show the 'filepath:row:col' when it fails, a future
improvement would be display it to easy find where the compilation
problem is located.

The ast_nodes are taking the token.value ownership (which is a really
bad design since not all token.value ownership has been taken causing
memory leaking) but we never free them.  For a future fix we could use a
string_view instead since we never change the original source code. The
string_view will also improve the performance a lot avoiding unnecessary
heap memory allocation.

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>
---
 src/parser.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 src/parser.c

(limited to 'src/parser.c')

diff --git a/src/parser.c b/src/parser.c
new file mode 100644
index 0000000..5d2a734
--- /dev/null
+++ b/src/parser.c
@@ -0,0 +1,102 @@
+/*
+* Copyright (C) 2023 Johnny Richard
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lexer.h"
+#include "parser.h"
+
+void
+parser_init(parser_t *parser, lexer_t *lexer)
+{
+  assert(parser && "parser must be defined");
+  assert(lexer && "lexer must be defined");
+  parser->lexer = lexer;
+}
+
+static token_t
+expected_token(parser_t *parser, token_kind_t kind)
+{
+  token_t token;
+  lexer_next_token(parser->lexer, &token);
+
+  if (token.kind == TOKEN_EOF) {
+    fprintf(stderr, "[ERROR]: expected '%s' but got end of file\n", token_kind_to_str(kind));
+    exit(EXIT_FAILURE);
+  }
+
+  if (token.kind != kind) {
+    fprintf(stderr, "[ERROR]: expected '%s' but got '%s'\n", token_kind_to_str(kind), token_kind_to_str(token.kind));
+    exit(EXIT_FAILURE);
+  }
+
+  return token;
+}
+
+static type_t
+parser_parse_type(parser_t *parser)
+{
+  token_t token = expected_token(parser, TOKEN_NAME);
+
+  if (strcmp(token.value, "i32") == 0) {
+    return TYPE_I32;
+  }
+
+  fprintf(stderr, "[ERROR]: expected type 'i32' but got '%s'\n", token.value); 
+  exit(EXIT_FAILURE);
+}
+
+static ast_return_stmt_t
+parser_parse_return_stmt(parser_t *parser)
+{
+  expected_token(parser, TOKEN_OCURLY);
+  token_t return_keyword_token = expected_token(parser, TOKEN_NAME);
+
+  if (strcmp(return_keyword_token.value, "return") != 0) {
+    // TODO: Add filename:row:col prefix to expected token exceptions
+    fprintf(stderr, "[ERROR]: expected 'return' keyword but got '%s'\n", return_keyword_token.value); 
+    exit(EXIT_FAILURE);
+  }
+
+  token_t number_token = expected_token(parser, TOKEN_NUMBER);
+  expected_token(parser, TOKEN_SEMICOLON);
+  expected_token(parser, TOKEN_CCURLY);
+
+  return (ast_return_stmt_t) {
+    .number = atoi(number_token.value)
+  };
+}
+
+ast_function_t
+parser_parse_function(parser_t *parser)
+{
+  token_t func_name_token = expected_token(parser, TOKEN_NAME);
+  expected_token(parser, TOKEN_OPAREN);
+  expected_token(parser, TOKEN_CPAREN);
+  expected_token(parser, TOKEN_COLON);
+  type_t return_type = parser_parse_type(parser);
+
+  return (ast_function_t) {
+    // FIXME: alloc memory for the ast_function.name, it's not a good idea to use the token.value
+    .name = func_name_token.value,
+    .return_type = return_type,
+    .body = parser_parse_return_stmt(parser)
+  };
+}
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