Add HeapSizeOf impl for ParseError

src/parser.rs

@@ -57,6 +57,9 @@ simple_enum_error! {
     Overflow => "URLs more than 4 GB are not supported",
 }
 
+#[cfg(feature = "heapsize")]
+known_heap_size!(0, ParseError);
+
 impl fmt::Display for ParseError {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
         self.description().fmt(fmt)