Update parser's disambiguation to cope with braced function-style casts in

C++11, and with braced-init-list initializers in conditions. This exposed an
ambiguity with enum underlying types versus bitfields, which we resolve by
treating 'enum E : T {' as always defining an enumeration (even if it would
only successfully parse as a bitfield). This appears to be g++ compatible.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@151227 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 96 insertions, 4 deletions

diff --git a/test/Parser/cxx0x-ambig.cpp b/test/Parser/cxx0x-ambig.cpp
new file mode 100644
index 0000000000..c955dc1690
--- /dev/null
+++ b/test/Parser/cxx0x-ambig.cpp
@@ -0,0 +1,92 @@
+// 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; };
+  namespace N {
+    int n;
+    // 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 {
+      int(n) // expected-error {{expected ';'}}
+    };
+  }
+}
+
+// enum versus bitfield mess.
+namespace bitfield {
+  enum E {};
+
+  struct T {
+    constexpr T() {}
+    constexpr T(int) {}
+    constexpr T(T, T, T, T) {}
+    constexpr T operator=(T) { return *this; }
+    constexpr operator int() { return 4; }
+  };
+  constexpr T a, b, c, d;
+
+  struct S1 {
+    enum E : T ( a = 1, b = 2, c = 3, 4 ); // ok, declares a bitfield
+  };
+  // This could be a bit-field.
+  struct S2 {
+    enum E : T { a = 1, b = 2, c = 3, 4 }; // expected-error {{non-integral type}} expected-error {{expected '}'}} expected-note {{to match}}
+  };
+  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 member name}}
+  };
+  // This could be a bit-field.
+  struct S6 {
+    enum E : int { 1 }; // expected-error {{expected '}'}} expected-note {{to match}}
+  };
+
+  struct U {
+    constexpr operator T() { 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}}
+  };
+}
+
+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}}
+      auto(a)()->n; // ok, function declaration
+      using T = decltype(a);
+      using T = auto() -> n;
+    }
+  }
+}
diff --git a/test/Parser/cxx0x-condition.cpp b/test/Parser/cxx0x-condition.cpp
index ce7d1a8aef..e45cd866ff 100644
--- a/test/Parser/cxx0x-condition.cpp
+++ b/test/Parser/cxx0x-condition.cpp
@@ -27,11 +27,11 @@ void f() {
   if (S b(n) = 0) {} // expected-error {{a function type is not allowed here}}
   if (S b(n) == 0) {} // expected-error {{a function type is not allowed here}} expected-error {{did you mean '='?}}
 
-  // FIXME: this is legal, and incorrectly rejected, because tentative parsing
-  // does not yet know about braced function-style casts.
-  if (S{a}) {} // unexpected-error{{unqualified-id}}
-
+  if (S{a}) {} // ok
   if (S a{a}) {} // ok
   if (S a = {a}) {} // ok
   if (S a == {a}) {} // expected-error {{did you mean '='?}}
+
+  if (S(b){a}) {} // ok
+  if (S(b) = {a}) {} // ok
 }