isCallable is not an expression

[andre via Digitalmars-d-learn]

Hi,
following code throws an error when I uncomment method 
getPropertyDuplicate.
getPropertyDuplicate is just a copy of getProperty except the 
method name.

Why these errors are thrown?

C:\D\dmd2\windows\bin\..\..\src\phobos\std\traits.d(1257): Error: 
isCallable!(ge
tPropertyDuplicate) is not an expression
source\app.d(25):        while looking for match for 
functionAttributes!(getProp
ertyDuplicate)
C:\D\dmd2\windows\bin\..\..\src\phobos\std\traits.d(1257): Error: 
template insta
nce std.traits.isCallable!(getPropertyDuplicate) error 
instantiating
source\app.d(11):        instantiated from here: 
functionAttributes!(getProperty
Duplicate)
source\app.d(11):        while looking for match for 
functionAttributes!(getProp
ertyDuplicate)

Kind regards
André

template MyTemplate()
{
	import std.traits : isSomeFunction, functionAttributes, 
FunctionAttribute, ReturnType;
	
	string[] getPropertyNames()
	{
		string[] result;
		foreach(m;__traits(allMembers, typeof(this)))
		{
			static if (isSomeFunction!(__traits(getMember, typeof(this), 
m))
			  && functionAttributes!(__traits(getMember, typeof(this), m)) 
& FunctionAttribute.property)
			{
					result ~= m;
			}
		}
		return result;
	}
	
	/*string[] getPropertyDuplicate()
	{
		string[] result;
		foreach(m;__traits(allMembers, typeof(this)))
		{
			static if (isSomeFunction!(__traits(getMember, typeof(this), 
m))
			  && functionAttributes!(__traits(getMember, typeof(this), m)) 
& FunctionAttribute.property)
			{
					result ~= m;
			}
		}
		return result;
	}*/
}

class A {
	mixin MyTemplate;
}

void main() {
	auto a = new A();
}