Report an error on undefined/undeclared functions

parse.c

@@ -925,6 +925,13 @@ static Node *funcall(Token **rest, Token *tok) {
   Token *start = tok;
   tok = tok->next->next;
 
+  VarScope *sc = find_var(start);
+  if (!sc)
+    error_tok(start, "implicit declaration of a function");
+  if (!sc->var || sc->var->ty->kind != TY_FUNC)
+    error_tok(start, "not a function");
+
+  Type *ty = sc->var->ty->return_ty;
   Node head = {};
   Node *cur = &head;
 
@@ -932,12 +939,14 @@ static Node *funcall(Token **rest, Token *tok) {
     if (cur != &head)
       tok = skip(tok, ",");
     cur = cur->next = assign(&tok, tok);
+    add_type(cur);
   }
 
   *rest = skip(tok, ")");
 
   Node *node = new_node(ND_FUNCALL, start);
   node->funcname = strndup(start->loc, start->len);
+  node->ty = ty;
   node->args = head.next;
   return node;
 }

test/test.h

@@ -1,3 +1,4 @@
 #define ASSERT(x, y) assert(x, y, #y)
 
+void assert(int expected, int actual, char *code);
 int printf();

tokenize.c

@@ -15,7 +15,7 @@ void error(char *fmt, ...) {
   exit(1);
 }
 
-// Reports an error message in the following format and exit.
+// Reports an error message in the following format.
 //
 // foo.c:10: x = y + 1;
 //               ^ <error message here>
@@ -40,7 +40,6 @@ static void verror_at(int line_no, char *loc, char *fmt, va_list ap) {
   fprintf(stderr, "^ ");
   vfprintf(stderr, fmt, ap);
   fprintf(stderr, "\n");
-  exit(1);
 }
 
 void error_at(char *loc, char *fmt, ...) {
@@ -52,12 +51,14 @@ void error_at(char *loc, char *fmt, ...) {
   va_list ap;
   va_start(ap, fmt);
   verror_at(line_no, loc, fmt, ap);
+  exit(1);
 }
 
 void error_tok(Token *tok, char *fmt, ...) {
   va_list ap;
   va_start(ap, fmt);
   verror_at(tok->line_no, tok->loc, fmt, ap);
+  exit(1);
 }
 
 // Consumes the current token if it matches `op`.