Add -> operator

parse.c

@@ -672,7 +672,7 @@ static Node *struct_ref(Node *lhs, Token *tok) {
   return node;
 }
 
-// postfix = primary ("[" expr "]" | "." ident)*
+// postfix = primary ("[" expr "]" | "." ident | "->" ident)*
 static Node *postfix(Token **rest, Token *tok) {
   Node *node = primary(&tok, tok);
 
@@ -692,6 +692,14 @@ static Node *postfix(Token **rest, Token *tok) {
       continue;
     }
 
+    if (equal(tok, "->")) {
+      // x->y is short for (*x).y
+      node = new_unary(ND_DEREF, node, tok);
+      node = struct_ref(node, tok->next);
+      tok = tok->next->next;
+      continue;
+    }
+
     *rest = tok;
     return node;
   }

test/struct.c

@@ -33,6 +33,9 @@ int main() {
   ASSERT(2, ({ struct t {char a[2];}; { struct t {char a[4];}; } struct t y; sizeof(y); }));
   ASSERT(3, ({ struct t {int x;}; int t=1; struct t y; y.x=2; t+y.x; }));
 
+  ASSERT(3, ({ struct t {char a;} x; struct t *y = &x; x.a=3; y->a; }));
+  ASSERT(3, ({ struct t {char a;} x; struct t *y = &x; y->a=3; x.a; }));
+
   printf("OK\n");
   return 0;
 }

tokenize.c

@@ -114,9 +114,11 @@ static int from_hex(char c) {
 
 // Read a punctuator token from p and returns its length.
 static int read_punct(char *p) {
-  if (startswith(p, "==") || startswith(p, "!=") ||
-      startswith(p, "<=") || startswith(p, ">="))
-    return 2;
+  static char *kw[] = {"==", "!=", "<=", ">=", "->"};
+
+  for (int i = 0; i < sizeof(kw) / sizeof(*kw); i++)
+    if (startswith(p, kw[i]))
+      return strlen(kw[i]);
 
   return ispunct(*p) ? 1 : 0;
 }