The Shl trait enables the << operator for types that implement it. This operator is used for left-shifting an integer by a number of bits, but has different meanings for various other data types.

The Shl trait has both an output associated type, and the option of implementing it to operate on different types by implementing Shl<OtherType> rather than just Shl.

ShlAssign has the same relationship to Shl that AddAssign has to Add.