Bug 2200 – std.string.format behaves wrong when passing an interface reference

Current std.string.format implementation throws an exception if an interface reference is passed to it.Although interfaces don't derive from an Object, an attempt to cast to an Object should be made, and no exception should be thrown unless the cast was unsuccessful. *Or* it should be a compile-time error to pass a reference to interface to the function. module test; interface I {} class C : I {} C c = new C(); I i = c; Object o = cast(Object)i; try { writefln( format(c) ); } catch (Exception e) { writefln(e); } try { writefln( format(i) ); } catch (Exception e) { writefln("Error: ", e); } try { writefln( format(o) ); } catch (Exception e) { writefln(e); } Expected behaviour: "test.C" printed 3 times Actual behaviour: and exception is thrown while in a format(i);

Currently writef/writefln fails with compile-time error deep inside std.format implementation with a "No property toString for test.I" error. It should be also updated to use cast to Object. Or, if it is made by design, std.string.format should fail with the same reason at compile-time.

*** This bug has been marked as a duplicate of 535 ***