It helps when you supply the full error (the full error is on the Output
page or on the command line). The full error is:

---8<---
error C2440: 'return' : cannot convert from '__const_Char_ptr' to
'wchar_t __gc *'
       Conversion loses qualifiers
--->8---

The problem is that __const_Char_ptr has a const qualifier, while the
declared return type of the function is non-const. You need to add
'const':

---8<---
const wchar_t __gc* GetAssemblyPath()
{
   return PtrToStringChars(Assembly::GetExecutingAssembly()->Location);
}
--->8---

Or alternatively, use const_cast<> to cast it away.

-- Barry