Merge pull request #4739 from Rageking8/improve-example-for-c2061

Improve example for C2061

Author: Jak-MS

docs/error-messages/compiler-errors-1/compiler-error-c2061.md

@@ -14,30 +14,54 @@ The compiler found an identifier where it wasn't expected. Make sure that `ident
 
 An initializer may be enclosed by parentheses. To avoid this problem, enclose the declarator in parentheses or make it a **`typedef`**.
 
-This error could also be caused when the compiler detects an expression as a class template argument; use [typename](../../cpp/typename.md) to tell the compiler it is a type.
+This error could also be caused when the compiler detects an expression as a class template argument; use [typename](../../cpp/typename.md) to tell the compiler it is a type, as shown in the following example:
 
 The following sample generates C2061:
 
 ```cpp
 // C2061.cpp
-// compile with: /c
-template < A a >   // C2061
-// try the following line instead
-// template < typename b >
-class c{};
+// compile with: /std:c++17
+
+template <A a> // C2061
+class C1 {};
+
+template <typename A a> // ok
+class C2 {};
+
+template <typename T>
+class C3
+{
+   // Both are valid since C++20
+   using Type1 = T::Type; // C2061
+   using Type2 = typename T::Type; // OK
+};
+
+int main()
+{
+   int x;
+   unsigned a1 = alignof(x);   // C2061
+   unsigned a2 = alignof(int); // OK
+   unsigned a3 = alignof(decltype(x)); // OK
+}
 ```
 
+To resolve the error with `template<A a> class C1{};`, use `template <typename a> class C1 {};`\
+To resolve the issue with `using Type1 = T::Type;`, use `using Type1 = typename T::Type;`\
+To resolve the issue with `alignof(x)`, replace the argument with the type of `x`. In this case, `int` or `decltype(x);`
+
 C2061 can occur if you pass an instance name to [typeid](../../extensions/typeid-cpp-component-extensions.md):
 
 ```cpp
 // C2061b.cpp
 // compile with: /clr
-ref struct G {
+ref struct G
+{
    int i;
 };
 
-int main() {
-   G ^ pG = gcnew G;
+int main()
+{
+   G ^pG = gcnew G;
    System::Type ^ pType = typeid<pG>;   // C2061
    System::Type ^ pType2 = typeid<G>;   // OK
 }