Add warnings for names reserved for metafunction implementations

Closes #720

Author: hsutter

include/cpp2util.h

@@ -260,6 +260,7 @@
 
 #define CPP2_TYPEOF(x)              std::remove_cvref_t<decltype(x)>
 #define CPP2_FORWARD(x)             std::forward<decltype(x)>(x)
+#define CPP2_PACK_EMPTY(x)          (sizeof...(x) == 0)
 #define CPP2_CONTINUE_BREAK(NAME)   goto CONTINUE_##NAME; CONTINUE_##NAME: continue; goto BREAK_##NAME; BREAK_##NAME: break;
                                     // these redundant goto's to avoid 'unused label' warnings
 

regression-tests/pure2-print.cpp2

@@ -49,7 +49,7 @@ outer: @print type = {
             return :() -> std::string = (s + m[0])$; ();
         }
 
-        values: <T> (this, t: T) throws -> (offset: int, name: std::string) = {
+        values: <T> (this, _: T) throws -> (offset: int, name: std::string) = {
             offset = 53;
             name = "plugh";
         }
@@ -60,7 +60,7 @@ outer: @print type = {
 
         operator=: (implicit out this, _: int) = { }
 
-        variadic: (x...: int) = { }
+        variadic: (x...: int) = { (std::cout << ... << x); }
     }
 
     test: () = {

regression-tests/pure2-variadics.cpp2

@@ -4,7 +4,7 @@ x: <Ts...: type> type = {
     tup: std::tuple<Ts...> = ();
 }
 
-print: <Args...: type> (inout out: std::ostream, args...: Args) = {
+left_fold_print: <Args...: type> (inout out: std::ostream, args...: Args) = {
     //  Binary left fold expression
     (out << ... << args);
 }
@@ -25,7 +25,7 @@ main: ()
     std::cout << make_string("plugh", :u8=3) << "\n";
     std::cout << make<std::string>("abracadabra", :u8=3) << "\n";
 
-    print( std::cout, 3.14, "word", -1500 );
+    left_fold_print( std::cout, 3.14, "word", -1500 );
 
     std::cout << "\nfirst all() returned (all(true, true, true, false))$";
     std::cout << "\nsecond all() returned " << all(true, true, true, true) as std::string;

regression-tests/test-results/clang-12/pure2-print.cpp.output

@@ -1,7 +0,0 @@
-pure2-print.cpp2:52:80: warning: unused parameter 't' [-Wunused-parameter]
-        template<typename T> [[nodiscard]] auto outer::mytype::values(T const& t) const& -> values_ret{
-                                                                               ^
-pure2-print.cpp2:63:53: warning: unused parameter 'x' [-Wunused-parameter]
-        auto outer::mytype::variadic(auto const& ...x) -> void{}
-                                                    ^
-2 warnings generated.

regression-tests/test-results/gcc-10/pure2-print.cpp.output

@@ -1,10 +1,17 @@
 In file included from pure2-print.cpp:7:
 ../../../include/cpp2util.h:10005:33: error: expected unqualified-id before ‘static_assert’
 pure2-print.cpp2:7:1: note: in expansion of macro ‘CPP2_REQUIRES_’
+pure2-print.cpp2:63:59: error: expected ‘;’ at end of member declaration
+In file included from pure2-print.cpp:7:
+../../../include/cpp2util.h:10005:47: error: static assertion failed: GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.
+pure2-print.cpp2:64:1: note: in expansion of macro ‘CPP2_REQUIRES_’
 ../../../include/cpp2util.h:10005:33: error: expected initializer before ‘static_assert’
 pure2-print.cpp2:89:1: note: in expansion of macro ‘CPP2_REQUIRES_’
 pure2-print.cpp2:6:29: error: ‘constexpr const T outer::object_alias’ is not a static data member of ‘class outer’
 pure2-print.cpp2:6:36: error: template definition of non-template ‘constexpr const T outer::object_alias’
+pure2-print.cpp2:63:14: error: no declaration matches ‘void outer::mytype::variadic(const auto:89& ...) requires (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(outer::mytype::variadic::x)>::type>::type, int> && ...)’
+pure2-print.cpp2:63:29: note: candidate is: ‘template<class ... auto:80> static void outer::mytype::variadic(const auto:80& ...)’
+pure2-print.cpp2:8:19: note: ‘class outer::mytype’ defined here
 pure2-print.cpp2:88:37: error: no declaration matches ‘void outer::print(std::ostream&, const Args& ...) requires  cpp2::cmp_greater_eq(sizeof (Args)..., 0)’
 pure2-print.cpp2:88:37: note: no functions named ‘void outer::print(std::ostream&, const Args& ...) requires  cpp2::cmp_greater_eq(sizeof (Args)..., 0)’
 pure2-print.cpp2:4:7: note: ‘class outer’ defined here

regression-tests/test-results/pure2-enum.cpp

@@ -24,9 +24,9 @@ class file_attributes;
 
 #line 2 "pure2-enum.cpp2"
 class skat_game {
-private: cpp2::i8 _value; private: constexpr skat_game(cpp2::in<cpp2::i64> val);
+private: cpp2::i8 _value; private: constexpr skat_game(cpp2::in<cpp2::i64> _val);
 
-private: constexpr auto operator=(cpp2::in<cpp2::i64> val) -> skat_game& ;
+private: constexpr auto operator=(cpp2::in<cpp2::i64> _val) -> skat_game& ;
 public: [[nodiscard]] constexpr auto get_raw_value() const& -> cpp2::i8;
 public: constexpr skat_game(skat_game const& that);
 public: constexpr auto operator=(skat_game const& that) -> skat_game& ;
@@ -54,9 +54,9 @@ class janus {
 #line 15 "pure2-enum.cpp2"
     public: constexpr auto flip() & -> void;
 
-        private: cpp2::i8 _value; private: constexpr janus(cpp2::in<cpp2::i64> val);
+        private: cpp2::i8 _value; private: constexpr janus(cpp2::in<cpp2::i64> _val);
 
-private: constexpr auto operator=(cpp2::in<cpp2::i64> val) -> janus& ;
+private: constexpr auto operator=(cpp2::in<cpp2::i64> _val) -> janus& ;
 public: [[nodiscard]] constexpr auto get_raw_value() const& -> cpp2::i8;
 public: constexpr janus(janus const& that);
 public: constexpr auto operator=(janus const& that) -> janus& ;
@@ -71,9 +71,9 @@ public: [[nodiscard]] auto to_string() const& -> std::string;
 };
 
 class file_attributes {
-private: cpp2::u8 _value; private: constexpr file_attributes(cpp2::in<cpp2::i64> val);
+private: cpp2::u8 _value; private: constexpr file_attributes(cpp2::in<cpp2::i64> _val);
 
-private: constexpr auto operator=(cpp2::in<cpp2::i64> val) -> file_attributes& ;
+private: constexpr auto operator=(cpp2::in<cpp2::i64> _val) -> file_attributes& ;
 public: [[nodiscard]] constexpr auto get_raw_value() const& -> cpp2::u8;
 public: constexpr file_attributes(file_attributes const& that);
 public: constexpr auto operator=(file_attributes const& that) -> file_attributes& ;
@@ -111,11 +111,11 @@ auto main() -> int;
 
 
 
-    constexpr skat_game::skat_game(cpp2::in<cpp2::i64> val)
-                                                         : _value{ cpp2::unsafe_narrow<cpp2::i8>(val) } {  }
-constexpr auto skat_game::operator=(cpp2::in<cpp2::i64> val) -> skat_game&  { 
-                                                         _value = cpp2::unsafe_narrow<cpp2::i8>(val);
-                                                         return *this; }
+    constexpr skat_game::skat_game(cpp2::in<cpp2::i64> _val)
+                                                          : _value{ cpp2::unsafe_narrow<cpp2::i8>(_val) } {  }
+constexpr auto skat_game::operator=(cpp2::in<cpp2::i64> _val) -> skat_game&  { 
+                                                          _value = cpp2::unsafe_narrow<cpp2::i8>(_val);
+                                                          return *this; }
 [[nodiscard]] constexpr auto skat_game::get_raw_value() const& -> cpp2::i8 { return _value; }
 constexpr skat_game::skat_game(skat_game const& that)
                                               : _value{ that._value }{}
@@ -155,12 +155,12 @@ inline CPP2_CONSTEXPR skat_game skat_game::null = 23;
     }
 
 
-    constexpr janus::janus(cpp2::in<cpp2::i64> val)
-                                                         : _value{ cpp2::unsafe_narrow<cpp2::i8>(val) } {  }
+    constexpr janus::janus(cpp2::in<cpp2::i64> _val)
+                                                          : _value{ cpp2::unsafe_narrow<cpp2::i8>(_val) } {  }
 
-constexpr auto janus::operator=(cpp2::in<cpp2::i64> val) -> janus&  { 
-                                                         _value = cpp2::unsafe_narrow<cpp2::i8>(val);
-                                                         return *this; }
+constexpr auto janus::operator=(cpp2::in<cpp2::i64> _val) -> janus&  { 
+                                                          _value = cpp2::unsafe_narrow<cpp2::i8>(_val);
+                                                          return *this; }
 [[nodiscard]] constexpr auto janus::get_raw_value() const& -> cpp2::i8 { return _value; }
 constexpr janus::janus(janus const& that)
                                               : _value{ that._value }{}
@@ -182,11 +182,11 @@ inline CPP2_CONSTEXPR janus janus::future = 1;
     return "invalid janus value"; 
     }
 
-    constexpr file_attributes::file_attributes(cpp2::in<cpp2::i64> val)
-                                                         : _value{ cpp2::unsafe_narrow<cpp2::u8>(val) } {  }
-constexpr auto file_attributes::operator=(cpp2::in<cpp2::i64> val) -> file_attributes&  { 
-                                                         _value = cpp2::unsafe_narrow<cpp2::u8>(val);
-                                                         return *this; }
+    constexpr file_attributes::file_attributes(cpp2::in<cpp2::i64> _val)
+                                                          : _value{ cpp2::unsafe_narrow<cpp2::u8>(_val) } {  }
+constexpr auto file_attributes::operator=(cpp2::in<cpp2::i64> _val) -> file_attributes&  { 
+                                                          _value = cpp2::unsafe_narrow<cpp2::u8>(_val);
+                                                          return *this; }
 [[nodiscard]] constexpr auto file_attributes::get_raw_value() const& -> cpp2::u8 { return _value; }
 constexpr file_attributes::file_attributes(file_attributes const& that)
                                               : _value{ that._value }{}
@@ -219,15 +219,15 @@ inline CPP2_CONSTEXPR file_attributes file_attributes::none = 0;
 
 [[nodiscard]] auto file_attributes::to_string() const& -> std::string{
 
-    std::string ret {"("}; 
+    std::string _ret {"("}; 
 
-    std::string comma {}; 
+    std::string _comma {}; 
     if ((*this) == none) {return "(none)"; }
-    if (((*this) & cached) == cached) {ret += comma + "cached";comma = ", ";}
-    if (((*this) & current) == current) {ret += comma + "current";comma = ", ";}
-    if (((*this) & obsolete) == obsolete) {ret += comma + "obsolete";comma = ", ";}
-    if (((*this) & cached_and_current) == cached_and_current) {ret += comma + "cached_and_current";comma = ", ";}
-    return ret + ")"; 
+    if (((*this) & cached) == cached) {_ret += _comma + "cached";_comma = ", ";}
+    if (((*this) & current) == current) {_ret += _comma + "current";_comma = ", ";}
+    if (((*this) & obsolete) == obsolete) {_ret += _comma + "obsolete";_comma = ", ";}
+    if (((*this) & cached_and_current) == cached_and_current) {_ret += _comma + "cached_and_current";_comma = ", ";}
+    return _ret + ")"; 
     }
 #line 28 "pure2-enum.cpp2"
 auto main() -> int{

regression-tests/test-results/pure2-print.cpp

@@ -38,7 +38,7 @@ CPP2_REQUIRES_ (true)
 
 
 #line 52 "pure2-print.cpp2"
-        public: template<typename T> [[nodiscard]] auto values(T const& t) const& -> values_ret;
+        public: template<typename T> [[nodiscard]] auto values([[maybe_unused]] T const& param2) const& -> values_ret;
 
 
 #line 57 "pure2-print.cpp2"
@@ -48,7 +48,10 @@ CPP2_REQUIRES_ (true)
 
         public: mytype([[maybe_unused]] cpp2::in<int> param2);
 
-        public: static auto variadic(auto const& ...x) -> void;
+        public: static auto variadic(auto const& ...x) -> void
+CPP2_REQUIRES_ ((std::is_convertible_v<CPP2_TYPEOF(x), int> && ...))
+#line 63 "pure2-print.cpp2"
+        ;
     };
 
     public: static auto test() -> void;
@@ -142,7 +145,7 @@ requires (true)
             return [_0 = (s + cpp2::assert_in_bounds(m, 0))]() -> std::string { return _0;  }(); 
         }
 
-        template<typename T> [[nodiscard]] auto outer::mytype::values(T const& t) const& -> values_ret{
+        template<typename T> [[nodiscard]] auto outer::mytype::values([[maybe_unused]] T const& param2) const& -> values_ret{
                 cpp2::deferred_init<int> offset;
                 cpp2::deferred_init<std::string> name;
 #line 53 "pure2-print.cpp2"
@@ -156,7 +159,10 @@ requires (true)
 
         outer::mytype::mytype([[maybe_unused]] cpp2::in<int> param2){}
 
-        auto outer::mytype::variadic(auto const& ...x) -> void{}
+        auto outer::mytype::variadic(auto const& ...x) -> void
+requires ((std::is_convertible_v<CPP2_TYPEOF(x), int> && ...))
+#line 63 "pure2-print.cpp2"
+        {(std::cout << ... << x); }
 
 #line 66 "pure2-print.cpp2"
     auto outer::test() -> void{

regression-tests/test-results/pure2-print.cpp2.output

@@ -80,7 +80,7 @@ outer: type =
 
         values: <T: type>(
             in this, 
-            in t: T
+            in _: T
         ) throws -> (
                 out offset: int, 
                 out name: std::string
@@ -111,6 +111,7 @@ outer: type =
 
         variadic:(in x...: int) = 
         {
+            (std::cout << ... << x);
         }
     }