llvm-project/clang/test/Parser/cxx0x-ambig.cpp

// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s

// New exciting ambiguities in C++11

// final 'context sensitive' mess.
namespace final {
  struct S { int n; };
  struct T { int n; };
  namespace N {
    int n;
    // These declare variables named final..
    extern struct S final;
    extern struct S final [[]];
    extern struct S final, foo;
    struct S final = S();

    // This defines a class, not a variable, even though it would successfully
    // parse as a variable but not as a class. DR1318's wording suggests that
    // this disambiguation is only performed on an ambiguity, but that was not
    // the intent.
    struct S final { // expected-note {{here}}
      int(n) // expected-error {{expected ';'}}
    };
    // This too.
    struct T final : S {}; // expected-error {{base 'S' is marked 'final'}}
    struct T bar : S {}; // expected-error {{expected ';' after top level declarator}} expected-error {{expected unqualified-id}}
  }
  // _Alignas isn't allowed in the places where alignas is. We used to
  // assert on this.
  struct U final _Alignas(4) {}; // expected-error 3{{}} expected-note {{}}
}

// enum versus bitfield. These are always required to be treated as an
// enum-base, but we disambiguate anyway for better error recovery.
namespace bitfield {
  enum E {};

  struct T {
    constexpr T() {}
    constexpr T(int) {}
    constexpr T(T, T, T, T) {}
    constexpr T operator=(T) const { return *this; }
    constexpr operator int() const { return 4; }
  };
  constexpr T a, b, c, d;

  struct S1 {
    enum E : T ( a = 1, b = 2, c = 3, 4 ); // expected-error {{ISO C++ only allows ':' in member enumeration declaration to introduce a fixed underlying type, not an anonymous bit-field}}
  };
  // Enum definition, not a bit-field.
  struct S2 {
    enum E : T { a = 1, b = 2, c = 3, 4 }; // expected-error {{non-integral type}} expected-error {{expected identifier}}
  };
  struct S3 {
    enum E : int { a = 1, b = 2, c = 3, d }; // ok, defines an enum
  };
  // Ambiguous.
  struct S4 {
    enum E : int { a = 1 }; // ok, defines an enum
  };
  // This could be a bit-field, but would be ill-formed due to the anonymous
  // member being initialized.
  struct S5 {
    enum E : int { a = 1 } { b = 2 }; // expected-error {{expected ';' after enum}} expected-error {{expected member name}}
  };
  // This could be a bit-field.
  struct S6 {
    enum E : int { 1 }; // expected-error {{expected identifier}}
  };

  struct U {
    constexpr operator T() const { return T(); } // expected-note 2{{candidate}}
  };
  // This could be a bit-field.
  struct S7 {
    enum E : int { a = U() }; // expected-error {{no viable conversion}}
  };
  // This could be a bit-field, and does not conform to the grammar of an
  // enum definition, because 'id(U())' is not a constant-expression.
  constexpr const U &id(const U &u) { return u; }
  struct S8 {
    enum E : int { a = id(U()) }; // expected-error {{no viable conversion}}
  };

  // PR26249: Disambiguate 'enum :' as an enum-base always, even if that would
  // be ill-formed. It cannot be an elaborated-type-specifier.
  struct S {
    enum : undeclared_type { v = 0 }; // expected-error {{unknown type name 'undeclared_type'}}
    enum E : undeclared_type { w = 0 }; // expected-error {{unknown type name 'undeclared_type'}}
    enum X : undeclared_type { x = 0 }; // expected-error {{unknown type name 'undeclared_type'}}
  };
}

namespace trailing_return {
  typedef int n;
  int a;

  struct S {
    S(int);
    S *operator()(...) const;
    int n;
  };

  namespace N {
    void f() {
      // This parses as a function declaration, but DR1223 makes the presence of
      // 'auto' be used for disambiguation.
      S(a)()->n; // ok, expression; expected-warning{{expression result unused}}
      S(a)(int())->n; // ok, expression; expected-warning{{expression result unused}}
      auto(a)()->n; // ok, function declaration
      auto(b)(int())->n; // ok, function declaration
      using T = decltype(a);
      using T = auto() -> n;
    }
  }
}

namespace ellipsis {
  template<typename...T>
  struct S {
    void e(S::S()); // expected-error {{is a constructor name}}
    void f(S(...args[sizeof(T)])); // expected-note {{here}} expected-note {{here}}
    void f(S(...args)[sizeof(T)]); // expected-error {{redeclared}}
    void f(S ...args[sizeof(T)]); // expected-error {{redeclared}}
    void g(S(...[sizeof(T)])); // expected-note {{here}} expected-warning {{ISO C++11 requires a parenthesized pack declaration to have a name}}
    void g(S(...)[sizeof(T)]); // expected-error {{function cannot return array type}}
    void g(S ...[sizeof(T)]); // expected-error {{redeclared}}
    void h(T(...)); // function type, expected-error {{unexpanded parameter pack}}
    void h(T...); // pack expansion, ok
    void i(int(T...)); // expected-note {{here}}
    void i(int(T...a)); // expected-error {{redeclared}}
    void i(int(T, ...)); // function type, expected-error {{unexpanded parameter pack}}
    void i(int(T, ...a)); // expected-error {{expected ')'}} expected-note {{to match}} expected-error {{unexpanded parameter pack}}
    void j(int(int...)); // function type, ok
    void j(int(int...a)); // expected-error {{does not contain any unexpanded parameter packs}}
    void j(T(int...)); // expected-error {{unexpanded parameter pack}}
    void j(T(T...)); // expected-error {{unexpanded parameter pack}}
    void k(int(...)(T)); // expected-error {{cannot return function type}}
    void k(int ...(T));
    void l(int(&...)(T)); // expected-warning {{ISO C++11 requires a parenthesized pack declaration to have a name}}
    void l(int(*...)(T)); // expected-warning {{ISO C++11 requires a parenthesized pack declaration to have a name}}
    void l(int(S<int>::*...)(T)); // expected-warning {{ISO C++11 requires a parenthesized pack declaration to have a name}}
  };

  struct CtorSink {
    template <typename ...T> constexpr CtorSink(T &&...t) { }
    constexpr operator int() const { return 42; }
  };

  template <unsigned ...N> struct UnsignedTmplArgSink;

  template <typename ...T>
  void foo(int x, T ...t) {
    // Have a variety of cases where the syntax is technically unambiguous, but hinges on careful treatment of ellipses.
    CtorSink(t ...), x; // ok, expression; expected-warning 2{{expression result unused}}

    int x0(CtorSink(t ...)); // ok, declares object x0
    int *p0 = &x0;
    (void)p0;

    CtorSink x1(int(t) ..., int(x)); // ok, declares object x1
    CtorSink *p1 = &x1;
    (void)p1;

    UnsignedTmplArgSink<T(CtorSink(t ...)) ...> *t0; // ok
    UnsignedTmplArgSink<((T *)0, 42u) ...> **t0p = &t0; // expected-warning 2{{left operand of comma operator has no effect}}
  }

  template void foo(int, int, int); // expected-note {{in instantiation of function template specialization 'ellipsis::foo<int, int>' requested here}}
}

namespace braced_init_list {
  struct X {
    void foo() {}
  };

  void (*pf1)() {};
  void (X::*pmf1)() {&X::foo};
  void (X::*pmf2)() = {&X::foo};

  void test() {
    void (*pf2)() {};
    void (X::*pmf3)() {&X::foo};
    void (X::*pmf4)() = {&X::foo};
  }
}