findSkip

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

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