RCString.opBinary

auto r1 = RCString("abc");
auto r2 = RCString("def");
assert((r1 ~ r2).equal("abcdef"));
assert((r1 ~ "foo").equal("abcfoo"));
assert(("abc" ~ r2).equal("abcdef"));
assert((r1 ~ 'd').equal("abcd"));
assert(('a' ~ r2).equal("adef"));

import std.range : take;
import std.utf : byCodeUnit;
auto r1 = RCString("abc");
auto r2 = "def".byCodeUnit.take(3);
assert((r1 ~ r2).equal("abcdef"));
assert((r2 ~ r1).equal("defabc"));