Type Patterns

The _Pattern Matching Basics_ lesson introduced the is operator and the switch expression as the two surfaces where pattern matching shows up. This lesson focuses on the patterns that test what an object's _type_ is: constant patterns, type patterns, the var pattern, the discard pattern, and how they combine when you dispatch on a class hierarchy. Property, positional, relational, logical, and list patterns are later lessons in this section, so leave those alone for now and concentrate on type-only matching.