Represents a long identifier with possible '.' at end. Typically dotRanges.Length = lid.Length-1, but they may be same if (incomplete) code ends in a dot, e.g. "Foo.Bar." The dots mostly matter for parsing, and are typically ignored by the typechecker, but if dotRanges.Length = lid.Length, then the parser must have reported an error, so the typechecker is allowed more freedom about typechecking these expressions. LongIdent can be empty list - it is used to denote that name of some AST element is absent (i.e. empty type name in inherit)