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digitalmars.D.bugs - [Issue 1730] New: const struct member func return invariant string can't assign to invariant string

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1730

           Summary: const struct member func return invariant string can't
                    assign to invariant string
           Product: D
           Version: 2.008
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: davidl 126.com


struct mystruct{
        invariant(char)[] toChars()
        {
                return "asdf";
        }
}
void func(in mystruct s)
{
        invariant(char)[] k=s.toChars;
}

testconst.d(9): function testconst.mystruct.toChars () does not match parameter
types ()
testconst.d(9): Error: s.toChars can only be called on a mutable object, not
const(mystruct)


--
Dec 13 2007
next sibling parent "Janice Caron" <caron800 googlemail.com> writes:
On 12/14/07, d-bugmail puremagic.com <d-bugmail puremagic.com> wrote:

 struct mystruct{
         invariant(char)[] toChars()
         {
                 return "asdf";
         }
 }
 void func(in mystruct s)
 {
         invariant(char)[] k=s.toChars;
 }



That's correct behaviour, surely?

Change the function definition to

    const invariant(char)[] toChars()
    {
        return "asdf";
    }

and the problem should go away. toChars() as written is incorrectly
declared. It does not modify this, therefore it should be declared
const.

That said, I don't understant how s got to be const in the first
place! Does "in" make things const?
Dec 13 2007
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1730


davidl 126.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |minor
           Keywords|rejects-valid               |
            Summary|const struct member func    |error message enhance?
                   |return invariant string     |
                   |can't assign to invariant   |
                   |string                      |




------- Comment #2 from davidl 126.com  2007-12-15 07:40 -------
But at least the first error message is confusing.


--
Dec 15 2007
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1730



--- Comment #3 from Stewart Gordon <smjg iname.com> 2009-11-20 11:10:48 PST ---
Probably part of the same bug:

----------
class Class {
    void fn1() const {
        fn2();
    }

    void fn2() {}
}
----------
const_call.d(3): Error: function const_call.Class.fn2 () is not callable using
argument types () const
----------

This may make sense at the internal level, as trying to convert the 'this'
argument implicitly from const(Class) to Class.  But as a user error message,
it's confusing.

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Nov 20 2009
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1730


Michal Spadlinski <gim913 gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gim913 gmail.com


--- Comment #4 from Michal Spadlinski <gim913 gmail.com> 2010-03-13 07:25:52
PST ---
I has similar problem with:

struct Foo {
    bool boo() {
        return false;
    }

    int foo () const {
        assert (boo);
        return 66;
    }
}

this message is totally misleading

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Mar 13 2010