//!
//! Suppose we have the following always applicable impl:
//!
-//! ```rust
+//! ```ignore (illustrative)
//! impl<T> SpecExtend<T> for std::vec::IntoIter<T> { /* specialized impl */ }
//! impl<T, I: Iterator<Item=T>> SpecExtend<T> for I { /* default impl */ }
//! ```