Bugfix for missing semaphore in typed template parameters. (hsutter#918)

* Bugfix for missing semaphore in typed template parameters.

* Output of unnamed type param name for typed template arguments.

* Name clash for unamed template arguments.

* Missing name generation of unamed template types in tempalte parameter list.

* Update of test results.

* Update for failing tests.

---------

Signed-off-by: Herb Sutter <[email protected]>
Co-authored-by: Herb Sutter <[email protected]>

Author: MaxSagebaum

regression-tests/pure2-variadics.cpp2

@@ -6,6 +6,27 @@ x: <Ts...: type> type = {
     func: () = {}
 }
 
+//  int pack expansion
+y: <Ts...: int> type = {
+
+    func: () ( 0 + ... + Ts);
+}
+
+// Discard type name pack expansion
+t0: @struct <_...> type = {
+  f: <_: int> () -> i32 = 0;
+}
+
+// Discard template type pack expansion
+t1: @struct <T...: _> type = {
+  f: <_: int> () -> i32 = 0;
+}
+
+// Discard typename and template type pack expansion
+t2: @struct <_...: _> type = {
+  f: <_: int> () -> i32 = 0;
+}
+
 left_fold_print: <Args...: type> (inout out: std::ostream, args...: Args) = {
     //  Binary left fold expression
     (out << ... << args);
@@ -31,4 +52,6 @@ main: ()
 
     std::cout << "\nfirst all() returned (all(true, true, true, false))$";
     std::cout << "\nsecond all() returned " << all(true, true, true, true) as std::string;
+
+    std::cout << "\nsum of (1, 2, 3, 100) is: " << y<1,2,3,100>().func() as std::string;
 }

regression-tests/test-results/apple-clang-14/pure2-variadics.cpp.execution

@@ -3,4 +3,5 @@ plu
 abr
 3.14word-1500
 first all() returned false
-second all() returned true
+second all() returned true
+sum of (1, 2, 3, 100) is: 106

regression-tests/test-results/gcc-10/pure2-variadics.cpp.execution

@@ -3,4 +3,5 @@ plu
 abr
 3.14word-1500
 first all() returned false
-second all() returned true
+second all() returned true
+sum of (1, 2, 3, 100) is: 106

regression-tests/test-results/gcc-13/pure2-variadics.cpp.execution

@@ -3,4 +3,5 @@ plu
 abr
 3.14word-1500
 first all() returned false
-second all() returned true
+second all() returned true
+sum of (1, 2, 3, 100) is: 106

regression-tests/test-results/mixed-bugfix-for-ufcs-non-local.cpp

@@ -34,15 +34,15 @@ namespace ns {
 
 // Variables.
 
-template<t<CPP2_UFCS_NONLOCAL(f)(o)> _> bool inline constexpr v0 = false;// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
+template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_13_6> bool inline constexpr v0 = false;// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
 
 t<CPP2_UFCS_NONLOCAL(f)(o)> inline constexpr v1 = t<true>();// Fails on Clang 12 (lambda in unevaluated context).
 
 bool inline constexpr v2 = CPP2_UFCS_NONLOCAL(f)(o);
 
 // Functions.
 
-template<t<CPP2_UFCS_NONLOCAL(f)(o)> _> auto g() -> void;
+template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_21_5> auto g() -> void;
 
 auto g([[maybe_unused]] cpp2::in<t<CPP2_UFCS_NONLOCAL(f)(o)>> unnamed_param_1) -> void;
 
@@ -52,9 +52,9 @@ auto g() -> void;
 
 // Aliases.
 
-template<t<CPP2_UFCS_NONLOCAL(f)(o)> _> using a = bool;// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
+template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_31_5> using a = bool;// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
 
-template<t<CPP2_UFCS_NONLOCAL(f)(o)> _> auto inline constexpr b = false;// Fails on GCC ([GCC109781][]).
+template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_33_5> auto inline constexpr b = false;// Fails on GCC ([GCC109781][]).
 
 using c = t<CPP2_UFCS_NONLOCAL(f)(o)>;// Fails on Clang 12 (lambda in unevaluated context) and Clang 12 (a lambda expression cannot appear in this context)
 
@@ -81,7 +81,7 @@ auto main() -> int;
 namespace ns {
 
 #line 21 "mixed-bugfix-for-ufcs-non-local.cpp2"
-template<t<CPP2_UFCS_NONLOCAL(f)(o)> _> auto g() -> void{}// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
+template<t<CPP2_UFCS_NONLOCAL(f)(o)> UnnamedTypeParam1_21_5> auto g() -> void{}// Fails on GCC ([GCC109781][]) and Clang 12 (a lambda expression cannot appear in this context)
 
 #line 23 "mixed-bugfix-for-ufcs-non-local.cpp2"
 auto g([[maybe_unused]] cpp2::in<t<CPP2_UFCS_NONLOCAL(f)(o)>> unnamed_param_1) -> void{}// Fails on Clang 12 (lambda in unevaluated context).

regression-tests/test-results/pure2-bugfix-for-ufcs-arguments.cpp

@@ -35,20 +35,20 @@ class B;
 class t {
   public: [[nodiscard]] auto f() & -> cpp2::i32;
   public: [[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_2) & -> cpp2::i32;
-  public: template<typename UnnamedTypeParam1> [[nodiscard]] auto f() & -> cpp2::i32;
-  public: template<typename UnnamedTypeParam1> [[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_2) & -> cpp2::i32;
-  public: template<typename UnnamedTypeParam1, typename U> [[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) & -> cpp2::i32;
+  public: template<typename UnnamedTypeParam1_10_7> [[nodiscard]] auto f() & -> cpp2::i32;
+  public: template<typename UnnamedTypeParam1_11_7> [[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_2) & -> cpp2::i32;
+  public: template<typename UnnamedTypeParam1_12_7, typename U> [[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) & -> cpp2::i32;
 };
 
 [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1) -> cpp2::i32;
 [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2) -> cpp2::i32;
-template<typename UnnamedTypeParam1> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1) -> cpp2::i32;
-template<typename UnnamedTypeParam1> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2) -> cpp2::i32;
-template<typename UnnamedTypeParam1, typename U> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) -> cpp2::i32;
+template<typename UnnamedTypeParam1_17_5> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1) -> cpp2::i32;
+template<typename UnnamedTypeParam1_18_5> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2) -> cpp2::i32;
+template<typename UnnamedTypeParam1_19_5, typename U> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) -> cpp2::i32;
 
 extern t m;
 extern t const n;
-template<typename UnnamedTypeParam1, typename U> auto inline constexpr a = n;
+template<typename UnnamedTypeParam1_23_5, typename U> auto inline constexpr a = n;
 
 extern cpp2::i32 auto_1;
 extern cpp2::i32 auto_2;
@@ -98,23 +98,17 @@ class B {
   [[nodiscard]] auto t::f() & -> cpp2::i32 { return print_res(0);  }
 #line 9 "pure2-bugfix-for-ufcs-arguments.cpp2"
   [[nodiscard]] auto t::f([[maybe_unused]] auto const& unnamed_param_2) & -> cpp2::i32 { return print_res(1);  }
-#line 10 "pure2-bugfix-for-ufcs-arguments.cpp2"
-  template<typename UnnamedTypeParam1> [[nodiscard]] auto t::f() & -> cpp2::i32 { return print_res(2);  }
-#line 11 "pure2-bugfix-for-ufcs-arguments.cpp2"
-  template<typename UnnamedTypeParam1> [[nodiscard]] auto t::f([[maybe_unused]] auto const& unnamed_param_2) & -> cpp2::i32 { return print_res(3);  }
-#line 12 "pure2-bugfix-for-ufcs-arguments.cpp2"
-  template<typename UnnamedTypeParam1, typename U> [[nodiscard]] auto t::f([[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) & -> cpp2::i32 { return print_res(4);  }
+  template<typename UnnamedTypeParam1_10_7> [[nodiscard]] auto t::f() & -> cpp2::i32 { return print_res(2);  }
+  template<typename UnnamedTypeParam1_11_7> [[nodiscard]] auto t::f([[maybe_unused]] auto const& unnamed_param_2) & -> cpp2::i32 { return print_res(3);  }
+  template<typename UnnamedTypeParam1_12_7, typename U> [[nodiscard]] auto t::f([[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) & -> cpp2::i32 { return print_res(4);  }
 
 #line 15 "pure2-bugfix-for-ufcs-arguments.cpp2"
 [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1) -> cpp2::i32 { return print_res(5);  }
 #line 16 "pure2-bugfix-for-ufcs-arguments.cpp2"
 [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2) -> cpp2::i32 { return print_res(6);  }
-#line 17 "pure2-bugfix-for-ufcs-arguments.cpp2"
-template<typename UnnamedTypeParam1> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1) -> cpp2::i32 { return print_res(7);  }
-#line 18 "pure2-bugfix-for-ufcs-arguments.cpp2"
-template<typename UnnamedTypeParam1> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2) -> cpp2::i32 { return print_res(8);  }
-#line 19 "pure2-bugfix-for-ufcs-arguments.cpp2"
-template<typename UnnamedTypeParam1, typename U> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) -> cpp2::i32 { return print_res(9);  }
+template<typename UnnamedTypeParam1_17_5> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1) -> cpp2::i32 { return print_res(7);  }
+template<typename UnnamedTypeParam1_18_5> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2) -> cpp2::i32 { return print_res(8);  }
+template<typename UnnamedTypeParam1_19_5, typename U> [[nodiscard]] auto f([[maybe_unused]] cpp2::in<t> unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3) -> cpp2::i32 { return print_res(9);  }
 
 t m {}; 
 t const n {}; 

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

@@ -12,6 +12,21 @@
 template<typename ...Ts> class x;
 
 
+#line 10 "pure2-variadics.cpp2"
+template<int ...Ts> class y;
+
+#line 16 "pure2-variadics.cpp2"
+template<typename ...UnnamedTypeParam1_16_14> class t0;
+  
+
+#line 21 "pure2-variadics.cpp2"
+template<auto ...T> class t1;
+  
+
+#line 26 "pure2-variadics.cpp2"
+template<auto ...UnnamedTypeParam1_26_14> class t2;
+  
+
 //=== Cpp2 type definitions and function declarations ===========================
 
 #line 1 "pure2-variadics.cpp2"
@@ -29,12 +44,38 @@ template<typename ...Ts> class x {
 #line 7 "pure2-variadics.cpp2"
 };
 
+//  int pack expansion
+template<int ...Ts> class y {
+
+    public: [[nodiscard]] static auto func() -> auto;
+    public: y() = default;
+    public: y(y const&) = delete; /* No 'that' constructor, suppress copy */
+    public: auto operator=(y const&) -> void = delete;
+
+#line 13 "pure2-variadics.cpp2"
+};
+
+// Discard type name pack expansion
+template<typename ...UnnamedTypeParam1_16_14> class t0 {
+  public: template<int UnnamedTypeParam1_17_7> [[nodiscard]] static auto f() -> cpp2::i32;
+};
+
+// Discard template type pack expansion
+template<auto ...T> class t1 {
+  public: template<int UnnamedTypeParam1_22_7> [[nodiscard]] static auto f() -> cpp2::i32;
+};
+
+// Discard typename and template type pack expansion
+template<auto ...UnnamedTypeParam1_26_14> class t2 {
+  public: template<int UnnamedTypeParam1_27_7> [[nodiscard]] static auto f() -> cpp2::i32;
+};
+
 template<typename ...Args> auto left_fold_print(std::ostream& out, Args const& ...args) -> void;
 
-#line 14 "pure2-variadics.cpp2"
+#line 35 "pure2-variadics.cpp2"
 template<typename ...Args> [[nodiscard]] auto all(Args const& ...args) -> bool;
 
-#line 18 "pure2-variadics.cpp2"
+#line 39 "pure2-variadics.cpp2"
 template     <typename ...Args> [[nodiscard]] auto make_string(Args&& ...args) -> auto;
 
 template  <typename T, typename ...Args> [[nodiscard]] auto make(Args&& ...args) -> auto;
@@ -48,7 +89,19 @@ auto main() -> int;
 #line 6 "pure2-variadics.cpp2"
     template <typename ...Ts> auto x<Ts...>::func() -> void{}
 
-#line 9 "pure2-variadics.cpp2"
+#line 12 "pure2-variadics.cpp2"
+    template <int ...Ts> [[nodiscard]] auto y<Ts...>::func() -> auto { return (0 + ... + Ts);  }
+
+#line 17 "pure2-variadics.cpp2"
+  template <typename ...UnnamedTypeParam1_16_14> template<int UnnamedTypeParam1_17_7> [[nodiscard]] auto t0<UnnamedTypeParam1_16_14...>::f() -> cpp2::i32 { return 0;  }
+
+#line 22 "pure2-variadics.cpp2"
+  template <auto ...T> template<int UnnamedTypeParam1_22_7> [[nodiscard]] auto t1<T...>::f() -> cpp2::i32 { return 0;  }
+
+#line 27 "pure2-variadics.cpp2"
+  template <auto ...UnnamedTypeParam1_26_14> template<int UnnamedTypeParam1_27_7> [[nodiscard]] auto t2<UnnamedTypeParam1_26_14...>::f() -> cpp2::i32 { return 0;  }
+
+#line 30 "pure2-variadics.cpp2"
 template<typename ...Args> auto left_fold_print(std::ostream& out, Args const& ...args) -> void{
     //  Binary left fold expression
     (out << ... << args);
@@ -78,5 +131,7 @@ auto main() -> int
 
     std::cout << ("\nfirst all() returned " + cpp2::to_string(all(true, true, true, false)));
     std::cout << "\nsecond all() returned " << cpp2::as_<std::string>(all(true, true, true, true));
+
+    std::cout << "\nsum of (1, 2, 3, 100) is: " << cpp2::as_<std::string>(CPP2_UFCS(func)(y<1,2,3,100>()));
 }
 

source/lex.h

@@ -336,6 +336,15 @@ auto labelized_position(token const* t)
     return labels[t].text;
 }
 
+auto unnamed_type_param_name(int ordinal, token const* t)
+    -> std::string
+{
+    return "UnnamedTypeParam"
+            + std::to_string(ordinal)
+            + "_"
+            + labelized_position(t);
+}
+
 
 //-----------------------------------------------------------------------
 //

source/to_cpp1.h

@@ -4277,9 +4277,8 @@ class cppfront
         //-----------------------------------------------------------------------
         //  Handle type parameters
 
-        if (n.declaration->is_type()) {
-            assert( is_template_parameter );
-            printer.print_cpp2("typename ", identifier_pos);
+        // Common template naming
+        auto emit_template_name = [&]() {
             if (n.declaration->is_variadic) {
                 printer.print_cpp2(
                     "...",
@@ -4288,12 +4287,18 @@ class cppfront
             }
 
             if (identifier == "_") {
-                printer.print_cpp2( "UnnamedTypeParam" + std::to_string(n.ordinal), identifier_pos );
+                printer.print_cpp2( unnamed_type_param_name(n.ordinal, n.declaration->identifier->get_token()),
+                                    identifier_pos );
             }
             else {
                 printer.print_cpp2( identifier, identifier_pos );
             }
+        };
+        if (n.declaration->is_type()) {
+            assert( is_template_parameter );
+            printer.print_cpp2("typename ", identifier_pos);
 
+            emit_template_name();
             return;
         }
 
@@ -4306,7 +4311,8 @@ class cppfront
         if (is_template_parameter) {
             emit( type_id );
             printer.print_cpp2(" ", type_id.position());
-                printer.print_cpp2( identifier, identifier_pos );
+
+            emit_template_name();
             return;
         }
 
@@ -4945,7 +4951,14 @@ class cppfront
                     auto separator = std::string{"<"};
                     for (auto& tparam : parent->template_parameters->parameters) {
                         assert (tparam->has_name());
-                        list += separator + tparam->name()->to_string();
+                        list += separator;
+                        if ("_" == tparam->name()->to_string()) {
+                            list += unnamed_type_param_name(tparam->ordinal,
+                                                            tparam->declaration->identifier->get_token());
+                        }
+                        else {
+                            list += tparam->name()->to_string();
+                        }
                         if(tparam->declaration->is_variadic) {
                             list += "...";
                         }