Support local function default template/ordinary parameters

This unlocks idioms useful in the regression tests, to disable test cases not supported on all compilers. An example that we can now do without macros:

    : <V: bool = gcc_clang_msvc_min_versions(1400, 1600, 1920)> () = {
        if constexpr V
        {
            // use std::views stuff without compiler bugs...
            // note this goes beyond what feature test macros allow,
            // because the feature may be implemented (and so
            // report it's available) but bugs may block the actual use
        }
    } ();

And expand boolean value string output to explicitly-boolean-convertible types

Author: hsutter

include/cpp2util.h

@@ -332,20 +332,42 @@
 #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
 
+//  Compiler version identification.
+// 
+//  This can use useful with 'if constexpr' to disable code known not to
+//  work on some otherwise-supported compilers (without macros), for example:
+// 
+//    //  Disable tests on lower-level compilers that have blocking bugs
+//    []<auto V = gcc_clang_msvc_min_versions(1400, 1600, 1920)> () { if constexpr (V) {
+//        // ... tests that would fail due to older compilers' bugs ...
+//    }}();
+//
+//  Note: Test Clang first because it pretends to be other compilers.
+//
 #if defined(__clang_major__)
-    constexpr auto CPP2_CLANG_VER = __clang_major__ * 100 + __clang_minor__;
-    constexpr auto CPP2_MSVC_VER  = 0;
-    constexpr auto CPP2_GCC_VER   = 0;
+    constexpr auto gcc_ver   = 0;
+    constexpr auto clang_ver = __clang_major__ * 100 + __clang_minor__;
+    constexpr auto msvc_ver  = 0;
 #elif defined(_MSC_VER)
-    constexpr auto CPP2_CLANG_VER = 0;
-    constexpr auto CPP2_MSVC_VER  = _MSC_VER;
-    constexpr auto CPP2_GCC_VER   = 0;
+    constexpr auto gcc_ver   = 0;
+    constexpr auto clang_ver = 0;
+    constexpr auto msvc_ver  = _MSC_VER;
 #elif defined(__GNUC__)
-    constexpr auto CPP2_CLANG_VER = 0;
-    constexpr auto CPP2_MSVC_VER  = 0;
-    constexpr auto CPP2_GCC_VER   = __GNUC__ * 100 + __GNUC_MINOR__;
+    constexpr auto gcc_ver   = __GNUC__ * 100 + __GNUC_MINOR__;
+    constexpr auto clang_ver = 0;
+    constexpr auto msvc_ver  = 0;
 #endif
 
+constexpr auto gcc_clang_msvc_min_versions(
+    auto gcc,
+    auto clang,
+    auto msvc
+)
+{
+    return gcc_ver > gcc || clang_ver > clang || msvc_ver > msvc;
+}
+
+
 #if defined(_MSC_VER)
    // MSVC can't handle 'inline constexpr' yet in all cases
     #define CPP2_CONSTEXPR const
@@ -1492,8 +1514,9 @@ inline auto to_string(auto const& x) -> std::string
         return x;
     }
 
-    //  Else customize bool (prefer this over << to avoid std::boolalpha)
-    if constexpr( std::is_same_v<CPP2_TYPEOF(x), bool> ) {
+    //  Else customize convertible-to-bool - use { } to avoid narrowing
+    if constexpr( requires{ bool{x}; } ) 
+    {
         return x ? "true" : "false";
     }
 

regression-tests/mixed-type-safety-1.cpp2

@@ -8,30 +8,18 @@ class Shape { public: virtual ~Shape() { } };
 class Circle : public Shape { };
 class Square : public Shape { };
 
-//--- printing helpers -----------------
 
-print: <T : type> ( msg: std::string, x: T ) 
-       requires !std::convertible_to<T, bool> =
-    std::cout << msg << x << "\n";
-
-print: ( msg: std::string, b: bool ) =
-{
-    bmsg: * const char;
-    if b { bmsg = "true";  }
-    else { bmsg = "false"; }
-    std::cout << msg << bmsg << "\n";
-}
-
-//--- examples -------------------------
+print: <T : type> ( msg: std::string, x: T ) =
+    std::cout << "(msg)$ (x)$\n";
 
 main: () -> int = 
 {
-    print( "1.1 is int? ", 1.1 is int );
-    print( "1   is int? ", 1   is int );
+    print( "1.1 is int?", 1.1 is int );
+    print( "1   is int?", 1   is int );
 
     c := new<Circle>();     // safe by construction
     s : * Shape = c.get();  // safe by Lifetime
-    print("\ns* is Shape?  ", s* is Shape  );
-    print(  "s* is Circle? ", s* is Circle );
-    print(  "s* is Square? ", s* is Square );
+    print("\ns* is Shape? ", s* is Shape  );
+    print(  "s* is Circle?", s* is Circle );
+    print(  "s* is Square?", s* is Square );
 }

regression-tests/pure2-default-arguments.cpp2

@@ -16,4 +16,14 @@ main: (args) = {
     f();
     f(1);
     f(2);
+
+    : <V: bool = gcc_clang_msvc_min_versions( 1400, 1600, 1920)> () = {
+        if constexpr V {
+            std::cout << "a newer compiler\n";
+        }
+        else {
+            std::cout << "an older compiler\n";
+        }
+    } ();
+
 }

regression-tests/pure2-range-operators.cpp2

@@ -38,19 +38,19 @@ main: () = {
     std::cout << "((1 ..< 20).contains(21))$\n";    // prints false
 
     //  Only run these parts on implementations that support views::take
-    // : <V: bool = (CPP2_GCC_VER > 1400 || CPP2_CLANG_VER > 1600 || CPP2_MSVC_VER > 1920)> () = {
-    //     if constexpr V
-    //     {
-    //         using std::views::_ ;
+    : <V: bool = gcc_clang_msvc_min_versions(1400, 1600, 1920)> () = {
+        if constexpr V
+        {
+            using std::views::_ ;
 
-    //         std::cout << "\nMake sure views::take works:\n";
-    //         for (1 ..= 100).take(5) do (e) {
-    //             std::cout << e << " ";
-    //         }   // prints: 1 2 3 4 5
-
-    //         for (2 ..< 5).take(5) do (e) {
-    //             std::cout << e << " ";
-    //         }   // prints: 2 3 4
-    //     }
-    // } ();
+            std::cout << "\nMake sure views::take works:\n";
+            for (1 ..= 100).take(5) do (e) {
+                std::cout << e << " ";
+            }   // prints: 1 2 3 4 5
+
+            for (2 ..< 5).take(5) do (e) {
+                std::cout << e << " ";
+            }   // prints: 2 3 4
+        }
+    } ();
 }

regression-tests/test-results/gcc-10-c++20/mixed-type-safety-1.cpp.output

@@ -6,12 +6,12 @@ pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:46: error: expect
 In file included from pure2-bugfix-for-requires-clause-in-forward-declaration.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-bugfix-for-requires-clause-in-forward-declaration.cpp2:4:1: note: in expansion of macro ‘CPP2_REQUIRES_’
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:3: error: no declaration matches ‘element::element(auto:95&&) requires  is_same_v<std::__cxx11::string, typename std::remove_cv<typename std::remove_reference<decltype(element::__ct ::n)>::type>::type>’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:3: error: no declaration matches ‘element::element(auto:98&&) requires  is_same_v<std::__cxx11::string, typename std::remove_cv<typename std::remove_reference<decltype(element::__ct ::n)>::type>::type>’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:5:11: note: candidates are: ‘element::element(const element&)’
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:20: note:                 ‘template<class auto:93> element::element(auto:93&&)’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:20: note:                 ‘template<class auto:96> element::element(auto:96&&)’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:1:7: note: ‘class element’ defined here
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:5:78: error: expected unqualified-id before ‘{’ token
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:8: error: no declaration matches ‘element& element::operator=(auto:96&&) requires  is_same_v<std::__cxx11::string, typename std::remove_cv<typename std::remove_reference<decltype(element::operator=::n)>::type>::type>’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:8: error: no declaration matches ‘element& element::operator=(auto:99&&) requires  is_same_v<std::__cxx11::string, typename std::remove_cv<typename std::remove_reference<decltype(element::operator=::n)>::type>::type>’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:6:16: note: candidates are: ‘void element::operator=(const element&)’
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:16: note:                 ‘template<class auto:94> element& element::operator=(auto:94&&)’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:16: note:                 ‘template<class auto:97> element& element::operator=(auto:97&&)’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:1:7: note: ‘class element’ defined here

regression-tests/test-results/gcc-10-c++20/pure2-bugfix-for-requires-clause-in-forward-declaration.cpp.output

@@ -1,66 +1,66 @@
 In file included from pure2-default-arguments.cpp:7:
 ../../../include/cpp2util.h:2086:28: error: local variable ‘obj’ may not appear in this context
- 2086 | 
-      |                            ^  
+ 2086 | auto as( std::variant<Ts...> & x ) -> decltype(auto) {
+      |                            ^~~
 ../../../include/cpp2util.h:2047:34: note: in definition of macro ‘CPP2_UFCS_IDENTITY’
- 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 8>(x)), T >) { if (x.index() ==  8) return operator_as<8>(x); }
+ 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<15>(x)), T >) { if (x.index() == 15) return true; }
       |                                  ^~~~~~~~~~~
 ../../../include/cpp2util.h:2086:15: note: in expansion of macro ‘CPP2_FORWARD’
- 2086 | 
-      |               ^           
+ 2086 | auto as( std::variant<Ts...> & x ) -> decltype(auto) {
+      |               ^~~~~~~~~~~~
 ../../../include/cpp2util.h:2107:22: note: in expansion of macro ‘CPP2_UFCS_CONSTRAINT_ARG’
- 2107 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<18>(x)), T >) { if (x.index() == 18) return operator_as<18>(x); }
+ 2107 |     Throw( std::bad_variant_access(), "'as' cast failed for 'variant'");
       |                      ^~~~~~~~~~~~~~~~~~~~~~~~
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 |     }
+ 2137 | //  std::any is and as
       |                                                           ^         
 pure2-default-arguments.cpp2:6:22: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 ../../../include/cpp2util.h:2086:92: error: local variable ‘params’ may not appear in this context
- 2086 | 
+ 2086 | auto as( std::variant<Ts...> & x ) -> decltype(auto) {
       |                                                                                            ^     
 ../../../include/cpp2util.h:2047:34: note: in definition of macro ‘CPP2_UFCS_IDENTITY’
- 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 8>(x)), T >) { if (x.index() ==  8) return operator_as<8>(x); }
+ 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<15>(x)), T >) { if (x.index() == 15) return true; }
       |                                  ^~~~~~~~~~~
 ../../../include/cpp2util.h:2086:79: note: in expansion of macro ‘CPP2_FORWARD’
- 2086 | 
+ 2086 | auto as( std::variant<Ts...> & x ) -> decltype(auto) {
       |                                                                               ^           
 ../../../include/cpp2util.h:2107:22: note: in expansion of macro ‘CPP2_UFCS_CONSTRAINT_ARG’
- 2107 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<18>(x)), T >) { if (x.index() == 18) return operator_as<18>(x); }
+ 2107 |     Throw( std::bad_variant_access(), "'as' cast failed for 'variant'");
       |                      ^~~~~~~~~~~~~~~~~~~~~~~~
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 |     }
+ 2137 | //  std::any is and as
       |                                                           ^         
 pure2-default-arguments.cpp2:6:22: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 ../../../include/cpp2util.h:2087:74: error: local variable ‘obj’ may not appear in this context
- 2087 | template<typename T, typename... Ts>
-      |                                                                          ^  
+ 2087 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 0>(x)), T >) { if (x.index() ==  0) return operator_as<0>(x); }
+      |                                                                          ^~~
 ../../../include/cpp2util.h:2047:34: note: in definition of macro ‘CPP2_UFCS_IDENTITY’
- 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 8>(x)), T >) { if (x.index() ==  8) return operator_as<8>(x); }
+ 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<15>(x)), T >) { if (x.index() == 15) return true; }
       |                                  ^~~~~~~~~~~
 ../../../include/cpp2util.h:2087:61: note: in expansion of macro ‘CPP2_FORWARD’
- 2087 | template<typename T, typename... Ts>
-      |                                                             ^           
+ 2087 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 0>(x)), T >) { if (x.index() ==  0) return operator_as<0>(x); }
+      |                                                             ^~~~~~~~~~~~
 ../../../include/cpp2util.h:2107:22: note: in expansion of macro ‘CPP2_UFCS_CONSTRAINT_ARG’
- 2107 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<18>(x)), T >) { if (x.index() == 18) return operator_as<18>(x); }
+ 2107 |     Throw( std::bad_variant_access(), "'as' cast failed for 'variant'");
       |                      ^~~~~~~~~~~~~~~~~~~~~~~~
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 |     }
+ 2137 | //  std::any is and as
       |                                                           ^         
 pure2-default-arguments.cpp2:6:22: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 ../../../include/cpp2util.h:2087:93: error: local variable ‘params’ may not appear in this context
- 2087 | template<typename T, typename... Ts>
-      |                                                                                             ^     
+ 2087 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 0>(x)), T >) { if (x.index() ==  0) return operator_as<0>(x); }
+      |                                                                                             ^~~~~~
 ../../../include/cpp2util.h:2047:34: note: in definition of macro ‘CPP2_UFCS_IDENTITY’
- 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 8>(x)), T >) { if (x.index() ==  8) return operator_as<8>(x); }
+ 2047 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<15>(x)), T >) { if (x.index() == 15) return true; }
       |                                  ^~~~~~~~~~~
 ../../../include/cpp2util.h:2087:80: note: in expansion of macro ‘CPP2_FORWARD’
- 2087 | template<typename T, typename... Ts>
-      |                                                                                ^           
+ 2087 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as< 0>(x)), T >) { if (x.index() ==  0) return operator_as<0>(x); }
+      |                                                                                ^~~~~~~~~~~~
 ../../../include/cpp2util.h:2107:22: note: in expansion of macro ‘CPP2_UFCS_CONSTRAINT_ARG’
- 2107 |     if constexpr (std::is_same_v< CPP2_TYPEOF(operator_as<18>(x)), T >) { if (x.index() == 18) return operator_as<18>(x); }
+ 2107 |     Throw( std::bad_variant_access(), "'as' cast failed for 'variant'");
       |                      ^~~~~~~~~~~~~~~~~~~~~~~~
 ../../../include/cpp2util.h:2137:59: note: in expansion of macro ‘CPP2_UFCS_’
- 2137 |     }
+ 2137 | //  std::any is and as
       |                                                           ^         
 pure2-default-arguments.cpp2:6:22: note: in expansion of macro ‘CPP2_UFCS_NONLOCAL’
 pure2-default-arguments.cpp2:6:61: error: ‘std::source_location’ has not been declared

regression-tests/test-results/gcc-10-c++20/pure2-default-arguments.cpp.output

@@ -9,8 +9,8 @@ pure2-print.cpp2:68:1: note: in expansion of macro ‘CPP2_REQUIRES_’
 pure2-print.cpp2:97:1: note: in expansion of macro ‘CPP2_REQUIRES_’
 pure2-print.cpp2:9:41: error: ‘constexpr const T outer::object_alias’ is not a static data member of ‘class outer’
 pure2-print.cpp2:9:48: error: template definition of non-template ‘constexpr const T outer::object_alias’
-pure2-print.cpp2:67:14: error: no declaration matches ‘void outer::mytype::variadic(const auto:94& ...) requires (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(outer::mytype::variadic::x)>::type>::type, int> && ...)’
-pure2-print.cpp2:67:29: note: candidate is: ‘template<class ... auto:93> static void outer::mytype::variadic(const auto:93& ...)’
+pure2-print.cpp2:67:14: error: no declaration matches ‘void outer::mytype::variadic(const auto:97& ...) requires (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(outer::mytype::variadic::x)>::type>::type, int> && ...)’
+pure2-print.cpp2:67:29: note: candidate is: ‘template<class ... auto:96> static void outer::mytype::variadic(const auto:96& ...)’
 pure2-print.cpp2:10:19: note: ‘class outer::mytype’ defined here
 pure2-print.cpp2:96:37: error: no declaration matches ‘void outer::print(std::ostream&, const Args& ...) requires  cpp2::impl::cmp_greater_eq(sizeof ... (Args ...), 0)’
 pure2-print.cpp2:96:37: note: no functions named ‘void outer::print(std::ostream&, const Args& ...) requires  cpp2::impl::cmp_greater_eq(sizeof ... (Args ...), 0)’

regression-tests/test-results/gcc-10-c++20/pure2-print.cpp.output

@@ -1 +1 @@
-mixed-bounds-safety-with-assert.cpp2(11) void print_subrange(const auto:105&, cpp2::impl::in<int>, cpp2::impl::in<int>) [with auto:105 = std::vector<int>; cpp2::impl::in<int> = const int]: Bounds safety violation
+mixed-bounds-safety-with-assert.cpp2(11) void print_subrange(const auto:108&, cpp2::impl::in<int>, cpp2::impl::in<int>) [with auto:108 = std::vector<int>; cpp2::impl::in<int> = const int]: Bounds safety violation