https://issues.dlang.org/show_bug.cgi?id=14236

          Issue ID: 14236
           Summary: opIndexUnary and opIndex fallback
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: john.loughran.colvin@gmail.com

struct S
{
    auto opIndex(size_t i)
    {
        return 1;
    }
    auto opIndexUnary(string s)(size_t i, size_t j)
    {
        return -1;
    }
}

unittest
{
    S s;
    assert(-s[0] == -1);
}

this fails to compile because the compiler won't fall back to using opIndex when it can't find an applicable opIndexUnary

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