Switched to bigint in lexer

new_lex.cpp

@@ -103,7 +103,7 @@ struct Token{
 
   union {
     U32 unicode;
-    U64 int_val;
+    BigInt int_val;
     F64 f64_val;
     String error_val;
     Intern_String intern_val;
@@ -209,19 +209,15 @@ token_error(Token *t, String error_val){
 function void
 lex_parse_u64(Token *t){
   t->kind = TK_Integer;
-  U64 result = 0;
-  U64 m = 1;
+  BigInt m = bigint_u64(1); // @leak, it accumulates and potentially needs allocation
+  BigInt val10 = bigint_u64(10);
+
   for(S64 i = t->len - 1; i >= 0; --i){
-    U64 val = t->str[i] - '0';
-    U64 new_val = val * m;
-    if((result + new_val) < result){
-      token_error(t, "Integer overflow"_s);
-      return;
-    }
-    result+=new_val;
-    m *= 10;
+    BigInt val = bigint_u64(t->str[i] - '0'); // I dont think this is a leak, too small
+    BigInt new_val = bigint_mul(&val, &m); // @leak
+    bigint_add(&t->int_val, &t->int_val, &new_val);
+    bigint_mul(&m, &m, &val10);
   }
-  t->int_val = result;
 }
 
 function void