PR0091R3: Implement parsing support for using templates as types.

This change adds a new type node, DeducedTemplateSpecializationType, to
represent a type template name that has been used as a type. This is modeled
around AutoType, and shares a common base class for representing a deduced
placeholder type.

We allow deduced class template types in a few more places than the standard
does: in conditions and for-range-declarators, and in new-type-ids. This is
consistent with GCC and with discussion on the core reflector. This patch
does not yet support deduced class template types being named in typename
specifiers.

llvm-svn: 293207

6 files changed, 156 insertions, 7 deletions

diff --git a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p5.cpp b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p5.cpp
index 0cdf3c6e053..a260f99f5cf 100644
--- a/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p5.cpp
+++ b/clang/test/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/p5.cpp
@@ -9,7 +9,7 @@ struct S {
 
   void f() throw (auto); // expected-error{{'auto' not allowed here}}
 
-  friend auto; // expected-error{{'auto' not allowed in non-static struct member}}
+  friend auto; // expected-error{{'auto' not allowed in friend declaration}}
 
   operator auto(); // expected-error{{'auto' not allowed in conversion function type}}
 };
diff --git a/clang/test/CXX/drs/dr5xx.cpp b/clang/test/CXX/drs/dr5xx.cpp
index 89e404f5fd6..cdb75219b1c 100644
--- a/clang/test/CXX/drs/dr5xx.cpp
+++ b/clang/test/CXX/drs/dr5xx.cpp
@@ -877,13 +877,25 @@ namespace dr583 { // dr583: 4
 namespace dr585 { // dr585: yes
   template<typename> struct T;
   struct A {
-    friend T; // expected-error {{requires a type specifier}} expected-error {{can only be classes or functions}}
+    friend T;
+#if __cplusplus <= 201402L
+    // expected-error@-2 {{requires a type specifier}} expected-error@-2 {{can only be classes or functions}}
+#else
+    // expected-error@-4 {{use of class template 'T' requires template arguments; argument deduction not allowed in friend declaration}}
+    // expected-note@-7 {{here}}
+#endif
     // FIXME: It's not clear whether the standard allows this or what it means,
     // but the DR585 writeup suggests it as an alternative.
     template<typename U> friend T<U>; // expected-error {{must use an elaborated type}}
   };
   template<template<typename> class T> struct B {
-    friend T; // expected-error {{requires a type specifier}} expected-error {{can only be classes or functions}}
+    friend T;
+#if __cplusplus <= 201402L
+    // expected-error@-2 {{requires a type specifier}} expected-error@-2 {{can only be classes or functions}}
+#else
+    // expected-error@-4 {{use of template template parameter 'T' requires template arguments; argument deduction not allowed in friend declaration}}
+    // expected-note@-6 {{here}}
+#endif
     template<typename U> friend T<U>; // expected-error {{must use an elaborated type}}
   };
 }
diff --git a/clang/test/Parser/backtrack-off-by-one.cpp b/clang/test/Parser/backtrack-off-by-one.cpp
index efb95a5a225..52e1c414783 100644
--- a/clang/test/Parser/backtrack-off-by-one.cpp
+++ b/clang/test/Parser/backtrack-off-by-one.cpp
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -verify %s
 // RUN: %clang_cc1 -verify %s -std=c++98
 // RUN: %clang_cc1 -verify %s -std=c++11
+// RUN: %clang_cc1 -verify %s -std=c++1z
 
 // PR25946
 // We had an off-by-one error in an assertion when annotating A<int> below.  Our
@@ -13,9 +14,13 @@ template <typename T> class A {};
 // expected-error@+1 {{expected '{' after base class list}}
 template <typename T> class B : T // not ',' or '{'
 #if __cplusplus < 201103L
-// expected-error@+4 {{expected ';' after top level declarator}}
+// expected-error@+8 {{expected ';' after top level declarator}}
+#endif
+#if __cplusplus <= 201402L
+// expected-error@+5 {{C++ requires a type specifier for all declarations}}
+#else
+// expected-error@+3 {{expected unqualified-id}}
 #endif
-// expected-error@+2 {{C++ requires a type specifier for all declarations}}
 // expected-error@+1 {{expected ';' after class}}
 A<int> {
 };
diff --git a/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp b/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
new file mode 100644
index 00000000000..e53d64f2ed4
--- /dev/null
+++ b/clang/test/Parser/cxx1z-class-template-argument-deduction.cpp
@@ -0,0 +1,131 @@
+// RUN: %clang_cc1 -std=c++1z -fcxx-exceptions -verify %s
+
+template<typename T> struct A {}; // expected-note 31{{declared here}}
+
+// Make sure we still correctly parse cases where a template can appear without arguments.
+namespace template_template_arg {
+  template<template<typename> typename> struct X {};
+  template<typename> struct Y {};
+
+  X<A> xa;
+  Y<A> ya; // expected-error {{requires template arguments}}
+  X<::A> xcca;
+  Y<::A> ycca; // expected-error {{requires template arguments}}
+
+  template<template<typename> typename = A> struct XD {};
+  template<typename = A> struct YD {}; // expected-error {{requires template arguments}}
+  template<template<typename> typename = ::A> struct XCCD {};
+  template<typename = ::A> struct YCCD {}; // expected-error {{requires template arguments}}
+
+  // FIXME: replacing the invalid type with 'int' here is horrible
+  template <A a = A<int>()> class C { }; // expected-error {{requires template arguments}} expected-error {{not implicitly convertible to 'int'}}
+  template<typename T = A> struct G { }; // expected-error {{requires template arguments}}
+}
+
+namespace injected_class_name {
+  template<typename T> struct A {
+    A(T);
+    void f(int) {
+      A a = 1;
+      injected_class_name::A b = 1; // expected-error {{not yet supported}}
+    }
+    void f(T);
+  };
+  A<short> ai = 1;
+  A<double>::A b(1); // expected-error {{constructor name}}
+}
+
+struct member {
+  A a; // expected-error {{requires template arguments}}
+  A *b; // expected-error {{requires template arguments}}
+  const A c; // expected-error {{requires template arguments}}
+
+  void f() throw (A); // expected-error {{requires template arguments}}
+
+  friend A; // expected-error {{requires template arguments; argument deduction not allowed in friend declaration}}
+
+  operator A(); // expected-error {{requires template arguments; argument deduction not allowed in conversion function type}}
+
+  static A x; // expected-error {{requires an initializer}}
+  static A y = 0; // expected-error {{not yet supported}}
+};
+
+namespace in_typedef {
+  typedef A *AutoPtr; // expected-error {{requires template arguments; argument deduction not allowed in typedef}}
+  typedef A (*PFun)(int a); // expected-error{{requires template arguments; argument deduction not allowed in typedef}}
+  typedef A Fun(int a) -> decltype(a + a); // expected-error{{requires template arguments; argument deduction not allowed in function return type}}
+}
+
+namespace stmt {
+  void g(A a) { // expected-error{{requires template arguments; argument deduction not allowed in function prototype}}
+    try { }
+    catch (A &a) { } // expected-error{{requires template arguments; argument deduction not allowed in exception declaration}}
+    catch (const A a) { } // expected-error{{requires template arguments; argument deduction not allowed in exception declaration}}
+    try { } catch (A a) { } // expected-error{{requires template arguments; argument deduction not allowed in exception declaration}}
+
+    // FIXME: The standard only permits class template argument deduction in a
+    // simple-declaration or cast. We also permit it in conditions,
+    // for-range-declarations, member-declarations for static data members, and
+    // new-expressions, because not doing so would be bizarre.
+    A local = 0; // expected-error {{not yet supported}}
+    static A local_static = 0; // expected-error {{not yet supported}}
+    static thread_local A thread_local_static = 0; // expected-error {{not yet supported}}
+    if (A a = 0) {} // expected-error {{not yet supported}}
+    if (A a = 0; a) {} // expected-error {{not yet supported}}
+    switch (A a = 0) {} // expected-error {{not yet supported}}
+    switch (A a = 0; a) {} // expected-error {{not yet supported}}
+    for (A a = 0; a; /**/) {} // expected-error {{not yet supported}}
+    for (/**/; A a = 0; /**/) {} // expected-error {{not yet supported}}
+    while (A a = 0) {} // expected-error {{not yet supported}}
+    int arr[3];
+    for (A a : arr) {} // expected-error {{not yet supported}}
+  }
+
+  namespace std {
+    class type_info;
+  }
+}
+
+namespace expr {
+  template<typename T> struct U {};
+  void j() {
+    (void)typeid(A); // expected-error{{requires template arguments; argument deduction not allowed here}}
+    (void)sizeof(A); // expected-error{{requires template arguments; argument deduction not allowed here}}
+    (void)__alignof(A); // expected-error{{requires template arguments; argument deduction not allowed here}}
+
+    U<A> v; // expected-error {{requires template arguments}}
+
+    int n;
+    (void)dynamic_cast<A&>(n); // expected-error{{requires template arguments; argument deduction not allowed here}}
+    (void)static_cast<A*>(&n); // expected-error{{requires template arguments; argument deduction not allowed here}}
+    (void)reinterpret_cast<A*>(&n); // expected-error{{requires template arguments; argument deduction not allowed here}}
+    (void)const_cast<A>(n); // expected-error{{requires template arguments; argument deduction not allowed here}}
+    (void)*(A*)(&n); // expected-error{{requires template arguments; argument deduction not allowed here}}
+
+    (void)A(n); // expected-error {{not yet supported}}
+    (void)A{n}; // expected-error {{not yet supported}}
+    (void)new A(n); // expected-error {{not yet supported}}
+    (void)new A{n}; // expected-error {{not yet supported}}
+    // FIXME: We should diagnose the lack of an initializer here.
+    (void)new A; // expected-error {{not yet supported}}
+  }
+}
+
+namespace decl {
+  enum E : A {}; // expected-error{{requires template arguments; argument deduction not allowed here}}
+  struct F : A {}; // expected-error{{expected class name}}
+
+  using B = A; // expected-error{{requires template arguments}}
+
+  auto k() -> A; // expected-error{{requires template arguments}}
+
+  A a; // expected-error {{requires an initializer}}
+  A b = 0; // expected-error {{not yet supported}}
+  A (parens) = 0; // expected-error {{cannot use parentheses when declaring variable with deduced class template specialization type}}
+  A *p = 0; // expected-error {{cannot form pointer to deduced class template specialization type}}
+  A &r = *p; // expected-error {{cannot form reference to deduced class template specialization type}}
+  A arr[3] = 0; // expected-error {{cannot form array of deduced class template specialization type}}
+  A F::*pm = 0; // expected-error {{cannot form pointer to deduced class template specialization type}}
+  A (*fp)() = 0; // expected-error {{cannot form function returning deduced class template specialization type}}
+  A [x, y] = 0; // expected-error {{cannot be declared with type 'A'}} expected-error {{not yet supported}}
+}
diff --git a/clang/test/SemaTemplate/temp_arg.cpp b/clang/test/SemaTemplate/temp_arg.cpp
index 052c19ef639..df5bf875f3b 100644
--- a/clang/test/SemaTemplate/temp_arg.cpp
+++ b/clang/test/SemaTemplate/temp_arg.cpp
@@ -10,7 +10,7 @@ A<int, 0, X> * a1;
 
 A<float, 1, X, double> *a2; // expected-error{{too many template arguments for class template 'A'}}
 A<float, 1> *a3; // expected-error{{too few template arguments for class template 'A'}}
-A a3; // expected-error{{use of class template 'A' requires template arguments}}
+A a4; // expected-error{{use of class template 'A' requires template arguments}}
 
 namespace test0 {
   template <class t> class foo {};
diff --git a/clang/test/SemaTemplate/typename-specifier-3.cpp b/clang/test/SemaTemplate/typename-specifier-3.cpp
index a463d88752c..dfab5a0130f 100644
--- a/clang/test/SemaTemplate/typename-specifier-3.cpp
+++ b/clang/test/SemaTemplate/typename-specifier-3.cpp
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 
 // PR4364
-template<class T> struct a {
+template<class T> struct a { // expected-note {{here}}
   T b() {
     return typename T::x();
   }
@@ -17,3 +17,4 @@ B c() {
 // Some extra tests for invalid cases
 template<class T> struct test2 { T b() { return typename T::a; } }; // expected-error{{expected '(' for function-style cast or type construction}}
 template<class T> struct test3 { T b() { return typename a; } }; // expected-error{{expected a qualified name after 'typename'}}
+template<class T> struct test4 { T b() { return typename ::a; } }; // expected-error{{refers to non-type member}} expected-error{{expected '(' for function-style cast or type construction}}