Before this commit, RandomAccessIndex was a refinement of
NumericOperations, which forced it to support inappropriate operations
such as multiplication. Many obvious random-access index types can't
support multiplication (e.g. a StridedIndex adapter, which moves its
underlying index by N positions for each increment).
Along the way:
* the addition and subtraction operations on RandomAccessIndex were
renamed to advancedBy and distanceTo, which prevents nasty ambiguities
when a type conforms to both RandomAccessIndex and Integer, and allows
Index DistanceTypes to actually be signed integers even when the Index
is unsigned.
* Before this commit, using internal interfaces, it was possible to
request static checking without also getting dynamic checks when
static checking is impossible. Now the relationship between static
and dynamic checking is built into the core protocols.
* NumericOperations.swift was moved into IntegerArithmetic.swift.gyb,
correcting missing operators by generating them programmatically and
in preparation for renaming the protocol to something more appropriate
Fixes
<rdar://problem/16246927> RandomAccessIndex is over-constrained
and possibly:
<rdar://problem/15605729> Make all operators generic over
protocols (in particular, get NumericOperations done)
Swift SVN r14854
