findLastSkip

const auto x = "abacc";
{
	string y = x;
	const bool ok = y.findLastSkip("_");
	assert(!ok);
	assert(y is x);
}
{
	string y = x;
	const bool ok = y.findLastSkip("a");
	assert(ok);
	assert(y == x[3 .. $]);
}
{
	string y = x;
	const bool ok = y.findLastSkip("c");
	assert(ok);
	assert(y is x[$ .. $]);
}
version (unittest) {
	static char[] f()() @safe pure nothrow { char[1] x = "_"; return x[].findLastSkip(" "); }
	static if (hasPreviewDIP1000) static assert(!__traits(compiles, { auto _ = f(); }));
}

const auto x = "abacc";
{
	string y = x;
	const bool ok = y.findLastSkip('_');
	assert(!ok);
	assert(y is x);
}
{
	string y = x;
	const bool ok = y.findLastSkip('a');
	assert(ok);
	assert(y == x[3 .. $]);
}
{
	string y = x;
	const bool ok = y.findLastSkip('c');
	assert(ok);
	assert(y is x[$ .. $]);
}
version (unittest) {
	static char[] f()() @safe pure nothrow { char[1] x = "_"; return x[].findLastSkip(' '); }
	static if (hasPreviewDIP1000) static assert(!__traits(compiles, { auto _ = f(); }));
}