parser: Ensure the expression types

When assign a variable or returning a value it now ensures that the
expression matches the expected type.

To make this possible a %result_type% field was added to ast_node_t and
this field is used whenever to make the comparison.

Signed-off-by: Carlos Maniero <carlos@maniero.me>
Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>

1 files changed, 49 insertions, 12 deletions

diff --git a/src/parser.c b/src/parser.c
index 22313a6..7a22f16 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -27,6 +27,9 @@
 #include "scope.h"
 #include "vector.h"
 
+static bool
+parser_expression_matches_the_expected_type(parser_t *parser, ast_node_t *expression, type_t type, token_t token);
+
 void
 parser_init(parser_t *parser, lexer_t *lexer, scope_t *scope)
 {
@@ -169,7 +172,8 @@ parser_parse_factor(parser_t *parser)
         return NULL;
       }
 
-      return ast_node_new_variable(&var_node->data.variable_declaration.identifier);
+      return ast_node_new_variable(&var_node->data.variable_declaration.identifier,
+                                   var_node->data.variable_declaration.type);
     }
     default: {
       parser_error_t error;
@@ -204,7 +208,7 @@ parser_parse_term(parser_t *parser)
       return NULL;
     }
 
-    node = ast_node_new_binary_operation(token_to_binary_operation_kind(&token), left, right);
+    node = ast_node_new_binary_operation(token_to_binary_operation_kind(&token), left, right, TYPE_I32);
 
     lexer_peek_next_token(parser->lexer, &token);
   }
@@ -242,7 +246,7 @@ parser_parse_expression(parser_t *parser)
       return NULL;
     }
 
-    node = ast_node_new_binary_operation(token_to_binary_operation_kind(&token), left, right);
+    node = ast_node_new_binary_operation(token_to_binary_operation_kind(&token), left, right, TYPE_I32);
 
     lexer_peek_next_token(parser->lexer, &token);
   }
@@ -251,23 +255,29 @@ parser_parse_expression(parser_t *parser)
 }
 
 static ast_node_t *
-parser_parse_return_stmt(parser_t *parser)
+parser_parse_return_stmt(parser_t *parser, type_t result_type)
 {
-  if (!drop_expected_token(parser, TOKEN_KEYWORD_RETURN)) {
+  token_t token;
+  if (!expected_token(&token, parser, TOKEN_KEYWORD_RETURN)) {
     return NULL;
   }
 
-  ast_node_t *argument_token = parser_parse_expression(parser);
-  if (argument_token == NULL) {
+  ast_node_t *expression = parser_parse_expression(parser);
+  if (expression == NULL) {
     return NULL;
   }
 
   if (!drop_expected_token(parser, TOKEN_SEMICOLON)) {
-    ast_node_destroy(argument_token);
+    ast_node_destroy(expression);
+    return NULL;
+  }
+
+  if (!parser_expression_matches_the_expected_type(parser, expression, result_type, token)) {
+    ast_node_destroy(expression);
     return NULL;
   }
 
-  return ast_node_new_return_stmt(argument_token);
+  return ast_node_new_return_stmt(expression);
 }
 
 static ast_node_t *
@@ -307,9 +317,31 @@ parser_parse_variable_assignment(parser_t *parser)
 
   assert(variable_declaration_node->kind == AST_VARIABLE_DECLARATION);
 
+  if (!parser_expression_matches_the_expected_type(
+        parser, expression, variable_declaration_node->data.variable_declaration.type, variable_token)) {
+    ast_node_destroy(expression);
+    return false;
+  }
+
   return ast_node_new_variable_assignment(&variable_declaration_node->data.variable_declaration.identifier, expression);
 }
 
+static bool
+parser_expression_matches_the_expected_type(parser_t *parser, ast_node_t *expression, type_t type, token_t token)
+{
+  if (expression->result_type != type) {
+    parser_error_t error;
+    error.token = token;
+    sprintf(error.message,
+            "incompatible types: expected '%s', actual '%s'.",
+            ast_type_to_str(type),
+            ast_type_to_str(expression->result_type));
+    parser->errors[parser->errors_len++] = error;
+    return false;
+  }
+  return true;
+}
+
 static ast_node_t *
 parser_parse_variable_declaration(parser_t *parser)
 {
@@ -348,6 +380,11 @@ parser_parse_variable_declaration(parser_t *parser)
     return NULL;
   }
 
+  if (!parser_expression_matches_the_expected_type(parser, expression, type, variable_name)) {
+    ast_node_destroy(expression);
+    return NULL;
+  }
+
   ast_node_t *node = ast_node_new_variable_declaration(variable_name.value, type, expression);
   scope_push(parser->scope, &node->data.variable_declaration.identifier, node);
 
@@ -426,7 +463,7 @@ parser_ensure_function_return_statement(parser_t *parser, vector_t *body, token_
 }
 
 static vector_t *
-parser_parse_block_declarations(parser_t *parser)
+parser_parse_block_declarations(parser_t *parser, type_t result_type)
 {
   if (!drop_expected_token(parser, TOKEN_OCURLY)) {
     return NULL;
@@ -441,7 +478,7 @@ parser_parse_block_declarations(parser_t *parser)
   while (!is_block_end(parser)) {
 
     if (is_next_statement_return(parser)) {
-      ast_node_t *return_node = parser_parse_return_stmt(parser);
+      ast_node_t *return_node = parser_parse_return_stmt(parser, result_type);
 
       if (return_node == NULL) {
         scope_leave(parser->scope);
@@ -529,7 +566,7 @@ parser_parse_function_declaration(parser_t *parser)
     return NULL;
   }
 
-  vector_t *body = parser_parse_block_declarations(parser);
+  vector_t *body = parser_parse_block_declarations(parser, return_type);
 
   if (body == NULL) {
     return NULL;