http://d.puremagic.com/issues/show_bug.cgi?id=3905

           Summary: Wrong error message with wrong opBinary("in")
           Product: D
           Version: 2.041
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-03-08 16:10:09 PST ---
This D2 program is wrong, because it needs a opBinaryRight to work:


struct Group {
    int i1, i2;
    bool opBinary(string s:"in")(int x) {
        return x == this.i1 || x == this.i2;
    }
}
auto enum r = 3 in Group(1, 2);
void main() {}


But the compiler gives a bad error message, that doesn't help the programmer much (and there are no associative arrays in this program):

test.d(7): Error: rvalue of in expression must be an associative array, not
Group

For example a better error message can be:

test.d(7): Error: Group has no opBinaryRight("in") operator and int has no
opBinary("in") operator.

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic, patch
                 CC|                            |clugdbug@yahoo.com.au


--- Comment #1 from Don <clugdbug@yahoo.com.au> 2010-09-30 01:37:09 PDT ---
PATCH:
expression.c, line 10624, InExp::semantic()


        default:
-            error("rvalue of in expression must be an associative array, not
%s", e2->type->toChars());
+            error("%s has no opBinaryRight(\"in\") operator and %s has no
opBinary(\"in\") operator", e1->type->toChars(), e2->type->toChars());
        case Terror:
            return new ErrorExp();
    }

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--- Comment #2 from bearophile_hugs@eml.cc 2010-09-30 05:10:35 PDT ---
Thank you Don :-) I need to be able to write a patch like this by myself.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |WONTFIX


--- Comment #3 from Walter Bright <bugzilla@digitalmars.com> 2010-12-04 18:36:08 PST ---
I'm not convinced this new error message is an improvement. All the expression error messages work on the assumption that operator overloads do not exist, as that is the normal case. Trying to write an error message for the normal case in terms of "you screwed up the operator overloads" is not helpful. For example,

  int a;
  double b;
  a in b;

will give a pretty much incomprehensible error message to the user:

  test.d(7): Error: double has no opBinaryRight("in") operator and int has no
  opBinary("in") operator.

???

I'd prefer to leave the message as is. If someone is doing operator overloading, the message makes it clear the operator overloading failed to find a match.

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Steven Schveighoffer <schveiguy@yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
                 CC|                            |schveiguy@yahoo.com
         Resolution|WONTFIX                     |


--- Comment #4 from Steven Schveighoffer <schveiguy@yahoo.com> 2010-12-04 22:46:00 PST ---
I agree that the proposed patch is not better.  But the original message is invalid.  This is a bug that needs to be fixed, regardless of whether you like the given proposals.

Point in fact, in *can* work on types besides associative arrays.

I tried this:

struct S {}

void main()
{
   S s;
   auto t = s + s;
}

And got:

Error: incompatible types for ((s) + (s)): 'S' and 'S'

So extrapolating to in, the error should look like:

Error: incompatible types for ((3) in (Group(1, 2))): 'int' and 'Group'

Although, I'm unsure why there are so many parentheses...

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--- Comment #5 from bearophile_hugs@eml.cc 2010-12-11 00:20:31 PST ---
Saying that double has no "in" is correct (even if it's a bit noisy and overkill), while saying "rvalue of in expression must be an associative array, not Group" is wrong.

I think this bug report is valid still, because the current error message is confusing. So a better solution will be useful.

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--- Comment #6 from yebblies <yebblies@gmail.com> 2013-01-17 02:14:10 EST ---
*** Issue 7837 has been marked as a duplicate of this issue. ***

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