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digitalmars.D - Non-conflicting derived class overload shadows base class method

reply "H. S. Teoh via Digitalmars-d" <digitalmars-d puremagic.com> writes:
Is this a bug?

	class A {
		int method();
	}
	class B : A {
		override void method(int);
	}
	void main() {
		B b;
		b.method(123);		// OK
		int x = b.method();	// NG
	}

One might question the wisdom of this kind of overloading, but this is
an actual use case in Phobos. In std.range.interfaces, we have:

	interface InputRange(E) {
		 property bool empty();
		 property E front();	// N.B. argumentless overload
		void popFront();
	}

	interface InputAssignable(E) : InputRange!E {
		 property void front(E e); // single argument overload
	}

The current shadowing behaviour makes InputAssignable fail to pass
isInputRange, because the derived interface's .front method shadows the
base class's, even though they are non-conflicting overloads(!).


T

-- 
"I'm running Windows '98." "Yes." "My computer isn't working now." "Yes, you
already said that." -- User-Friendly
Mar 20 2017
parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Monday, 20 March 2017 at 19:57:03 UTC, H. S. Teoh wrote:

 Is this a bug?


No, that's intentional, you have to merge the overload sets with 
alias, same as if you imported them from two separate modules.

http://dlang.org/hijack.html
Mar 20 2017
parent Jonathan M Davis via Digitalmars-d <digitalmars-d puremagic.com> writes:
On Monday, March 20, 2017 20:13:12 Adam D. Ruppe via Digitalmars-d wrote:

 On Monday, 20 March 2017 at 19:57:03 UTC, H. S. Teoh wrote:

 Is this a bug?


 No, that's intentional, you have to merge the overload sets with
 alias, same as if you imported them from two separate modules.

 http://dlang.org/hijack.html


Yeah. Creating new overloads for functions from a base class gets annoying
fast. It's probably great from the standpoint of avoiding function hijacking
bugs, but as with many of the restrictions that we get as part of the
attempts to avoid function hijacking in D, the result can be a bit annoying
in practice.

- Jonathan M Davis
Mar 20 2017