I would refactor this as a new `isMethodConst` template to avoid duplication and add a unit test for it too. Something along the lines of:

```d
/**
 * Returns true if the passed function is const, false if not.
 *
 * Params:
 *     func = The function to inspect.
 */
private template isMethodConst(func...) if (func.length == 1 && isCallable!(func))
{
	enum isMethodConst = !isMutable!(FunctionTypeOf!(func));
}

unittest
{
	class T
	{
		public void method1() const {}
		public void method2() immutable {}
		public void method3(){}
	}

	isMethodConst!(T.method1).assertTrue();
	isMethodConst!(T.method2).assertTrue();
	isMethodConst!(T.method3).assertFalse();
}
```