I'm creating this as a regression as the below code was valid in DMD 2.069 but no longer works in 2.070. It was introduced by this[1] commit. Though it may be better to consider this a feature request to make the error message more reasonable.

1. https://github.com/D-Programming-Language/phobos/commit/b6a61d9e719a9d680936db44b98fbb5dd28bf6b1

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    import std.algorithm;

    void main() {
        auto str = "sep,one,sep,two";

        auto split = str.findSplitAfter(",");
        assert(split[0] == "sep,");
        split = split[1].findSplitAfter(",");
        assert(split[0] == "one,");
        split = split[1].findSplitBefore(",");
        assert(split[0] == "sep");
    }
-------------------------

test.d(10): Error: function std.algorithm.searching.findSplitAfter!("a == b", string, string).findSplitAfter.Result!(str
ing, string).Result.opAssign (Result!(string, string) p) is not callable using argument types (Result!(string, string))