Decoder has the same semantics as Setter, but takes higher precedence. It is provided for historical compatibility.

A ParseError occurs when an environment variable cannot be converted to the type required by a struct field during assignment.

Setter is implemented by types can self-deserialize values. Any type that implements flag.Value also implements Setter.

quoted is used to test the precedence of Decode over Set. The sole field is a flag.Value rather than a setter to validate that all flag.Value implemen

varInfo maintains information about the configuration variable