// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf 
#define msg "p202.cpp(91)8.2 Ambiguity resolution [dcl.ambig.res]"

#include <iostream>

struct S {
  S(int);
};
void foo(double a) {
  S w(int(a)); // function declaration
  S x(int()); // function declaration
  S y((int(a))); // object declaration
  S y2((int)a); // object declaration
  S z = int(a); // object declaration
}
template struct X {};
template struct Y {};
X a; // type-id
X b; // expression (ill-formed)
Y c; // type-id (ill-formed)
Y d; // expression
void foo(signed char a) {
  sizeof(int()); // type-id (ill-formed)
  sizeof(int(a)); // expression
  sizeof(int(unsigned(a))); // type-id (ill-formed)
  (int())+1; // type-id (ill-formed)
  (int(a))+1; // expression
  (int(unsigned(a)))+1; // type-id (ill-formed)
}
class C { };
void f(int(C)) { } // void f(int(*fp)(C c)) { }
// not: void f(int C);
int g(C);
void foo() {
  f(1); // error: cannot convert 1 to function pointer
  f(g); // OK
}
class C { };
void h(int (C[10])); // void h(int *(_fp)(C _parm[10]));
// not: void h(int *C[10]);

int main(){
  foo();
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p202
$ clang++ p202.cpp
p202.cpp:11:6: warning: parentheses were disambiguated as a function declaration [-Wvexing-parse]
  S w(int(a)); // function declaration
     ^~~~~~~~
p202.cpp:11:7: note: add a pair of parentheses to declare a variable
  S w(int(a)); // function declaration
      ^
      (     )
p202.cpp:12:6: warning: parentheses were disambiguated as a function declaration [-Wvexing-parse]
  S x(int()); // function declaration
     ^~~~~~~
p202.cpp:12:7: note: add a pair of parentheses to declare a variable
  S x(int()); // function declaration
      ^
      (    )
p202.cpp:17:19: error: class cannot be defined in an explicit instantiation; if this declaration is meant to be a class definition, remove
      the 'template' keyword
template struct X {};
~~~~~~~~~         ^
p202.cpp:18:19: error: class cannot be defined in an explicit instantiation; if this declaration is meant to be a class definition, remove
      the 'template' keyword
template struct Y {};
~~~~~~~~~         ^
p202.cpp:24:3: error: invalid application of 'sizeof' to a function type
  sizeof(int()); // type-id (ill-formed)
  ^     ~~~~~~~
p202.cpp:26:3: error: invalid application of 'sizeof' to a function type
  sizeof(int(unsigned(a))); // type-id (ill-formed)
  ^     ~~~~~~~~~~~~~~~~~~
p202.cpp:27:3: error: C-style cast from 'int' to 'int ()' is not allowed
  (int())+1; // type-id (ill-formed)
  ^~~~~~~~~
p202.cpp:29:3: error: C-style cast from 'int' to 'int (unsigned int)' is not allowed
  (int(unsigned(a)))+1; // type-id (ill-formed)
  ^~~~~~~~~~~~~~~~~~~~
p202.cpp:25:3: warning: expression result unused [-Wunused-value]
  sizeof(int(a)); // expression
  ^~~~~~~~~~~~~~
p202.cpp:28:11: warning: expression result unused [-Wunused-value]
  (int(a))+1; // expression
  ~~~~~~~~^~
p202.cpp:36:3: error: no matching function for call to 'f'
  f(1); // error: cannot convert 1 to function pointer
  ^
p202.cpp:32:6: note: candidate function not viable: no known conversion from 'int' to 'int (*)(C)' for 1st argument
void f(int(C)) { } // void f(int(*fp)(C c)) { }
     ^
p202.cpp:39:7: error: redefinition of 'C'
class C { };
      ^
p202.cpp:31:7: note: previous definition is here
class C { };
      ^
4 warnings and 8 errors generated.

$ g++-7 p202.cpp
p202.cpp:17:20: error: explicit instantiation of non-template type 'X'
 template struct X {};
                    ^
p202.cpp:18:20: error: explicit instantiation of non-template type 'Y'
 template struct Y {};
                    ^
p202.cpp: In function 'void foo(signed char)':
p202.cpp:24:15: warning: invalid application of 'sizeof' to a function type [-Wpointer-arith]
   sizeof(int()); // type-id (ill-formed)
               ^
p202.cpp:26:26: warning: invalid application of 'sizeof' to a function type [-Wpointer-arith]
   sizeof(int(unsigned(a))); // type-id (ill-formed)
                          ^
p202.cpp:27:11: error: invalid cast to function type 'int()'
   (int())+1; // type-id (ill-formed)
           ^
p202.cpp:29:22: error: invalid cast to function type 'int(unsigned int)'
   (int(unsigned(a)))+1; // type-id (ill-formed)
                      ^
p202.cpp: In function 'void foo()':
p202.cpp:36:6: error: invalid conversion from 'int' to 'int (*)(C)' [-fpermissive]
   f(1); // error: cannot convert 1 to function pointer
      ^
p202.cpp:32:6: note:   initializing argument 1 of 'void f(int (*)(C))'
 void f(int(C)) { } // void f(int(*fp)(C c)) { }
      ^
p202.cpp: At global scope:
p202.cpp:39:7: error: redefinition of 'class C'
 class C { };
       ^
p202.cpp:31:7: note: previous definition of 'class C'
 class C { };
       ^