[Issue 3969] New: Built-in compile time errors against usage of wrong operator strings

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3969

           Summary: Built-in compile time errors against usage of wrong
                    operator strings
           Product: D
           Version: 2.041
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: bearophile_hugs at eml.cc


--- Comment #0 from bearophile_hugs at eml.cc 2010-03-15 10:47:02 PDT ---
This D2 code runs:


struct Foo {
    int data;
    bool opBinary(string Op:"==")(ref const Foo other) { // wrong: opEquals
        return this.data == other.data;
    }
    bool opBinary(string Op)(ref const Foo other) if (Op == "0") { // wrong
        return this.data == other.data;
    }
}
void main() {}


But that can cause bugs: it's easy for programmers to forget to use opEquals
instead of opBinary("==").

And generally I'd like dmd to raise an error when silly ops are defined, like
that "0". It's important to avoid many bugs in the operator overloading usage.

---------

Steven Schveighoffer>These kinds of errors are appropriate for a lint tool.<

Generally any compiler error can be moved to a lint tool, so it's a matter of
balance. In my opinion generally if some sanity test on the code is
computationally heavy or the errors it spots are uncommon, or if it's not
certain they are really errors, or if it's very uncommon, then it's possible or
better to move it to a lint. If the test is not hard/heavy to do and it can
catch a common sure mistake then it's better to put it into the compiler. D
compiler already performs several tests that were work for C lint tools.

So I think the compiler can be allowed to catch some potentially common
operator overloading bugs like opBinary("==").

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