Support _ unnamed type parameters - closes #812

Also require an `operator=` second parameter of the same type to be named `that` - see #475 discussion thread

Author: hsutter

regression-tests/test-results/mixed-bounds-safety-with-assert-2.cpp

@@ -43,7 +43,7 @@ auto add_42_to_subrange(auto& rng, cpp2::in<int> start, cpp2::in<int> end) -> vo
     auto count {0}; 
     for ( 
 
-          auto&  i : rng )  { do 
+          auto& i : rng )  { do 
         if ([_0 = start, _1 = count, _2 = end]{ return cpp2::cmp_less_eq(_0,_1) && cpp2::cmp_less_eq(_1,_2); }()) {
             i += 42;
         } while (false); ++count; }

regression-tests/test-results/mixed-forwarding.cpp

@@ -20,9 +20,9 @@ struct X {
 };
 
 #line 11 "mixed-forwarding.cpp2"
-auto copy_from([[maybe_unused]] auto param1) -> void;
+auto copy_from([[maybe_unused]] auto unnamed_param_1) -> void;
 
-auto use([[maybe_unused]] auto const& param1) -> void;
+auto use([[maybe_unused]] auto const& unnamed_param_1) -> void;
 
 // invoking each of these with an rvalue std::pair argument ...
 auto apply_implicit_forward(auto&& t) -> void
@@ -46,9 +46,9 @@ CPP2_REQUIRES (std::is_same_v<CPP2_TYPEOF(t), std::pair<X,X>>)
 
 
 #line 11 "mixed-forwarding.cpp2"
-auto copy_from([[maybe_unused]] auto param1) -> void{}
+auto copy_from([[maybe_unused]] auto unnamed_param_1) -> void{}
 
-auto use([[maybe_unused]] auto const& param1) -> void{}
+auto use([[maybe_unused]] auto const& unnamed_param_1) -> void{}
 
 #line 16 "mixed-forwarding.cpp2"
 auto apply_implicit_forward(auto&& t) -> void

regression-tests/test-results/mixed-parameter-passing-with-forward.cpp

@@ -15,12 +15,12 @@
 #include <ctime>
 
 #line 6 "mixed-parameter-passing-with-forward.cpp2"
-auto copy_from([[maybe_unused]] auto param1) -> void;
+auto copy_from([[maybe_unused]] auto unnamed_param_1) -> void;
 
 auto parameter_styles(
-    [[maybe_unused]] cpp2::in<std::string> param1, // "in" is default
+    [[maybe_unused]] cpp2::in<std::string> unnamed_param_1, // "in" is default
     std::string b, 
-    [[maybe_unused]] std::string& param3, 
+    [[maybe_unused]] std::string& unnamed_param_3, 
     std::string&& d, 
     auto&& e
     ) -> void
@@ -36,12 +36,12 @@ CPP2_REQUIRES (std::is_same_v<CPP2_TYPEOF(e), std::string>)
 
 
 #line 6 "mixed-parameter-passing-with-forward.cpp2"
-auto copy_from([[maybe_unused]] auto param1) -> void{}
+auto copy_from([[maybe_unused]] auto unnamed_param_1) -> void{}
 
 auto parameter_styles(
-    [[maybe_unused]] cpp2::in<std::string> param1, 
+    [[maybe_unused]] cpp2::in<std::string> unnamed_param_1, 
     std::string b, 
-    [[maybe_unused]] std::string& param3, 
+    [[maybe_unused]] std::string& unnamed_param_3, 
     std::string&& d, 
     auto&& e
     ) -> void

regression-tests/test-results/mixed-parameter-passing.cpp

@@ -15,12 +15,12 @@
 #include <ctime>
 
 #line 6 "mixed-parameter-passing.cpp2"
-auto copy_from([[maybe_unused]] auto param1) -> void;
+auto copy_from([[maybe_unused]] auto unnamed_param_1) -> void;
 
 auto parameter_styles(
-    [[maybe_unused]] cpp2::in<std::string> param1, // "in" is default
+    [[maybe_unused]] cpp2::in<std::string> unnamed_param_1, // "in" is default
     std::string b, 
-    [[maybe_unused]] std::string& param3, 
+    [[maybe_unused]] std::string& unnamed_param_3, 
     std::string&& d
     ) -> void;
 
@@ -32,12 +32,12 @@ auto parameter_styles(
 
 
 #line 6 "mixed-parameter-passing.cpp2"
-auto copy_from([[maybe_unused]] auto param1) -> void{}
+auto copy_from([[maybe_unused]] auto unnamed_param_1) -> void{}
 
 auto parameter_styles(
-    [[maybe_unused]] cpp2::in<std::string> param1, 
+    [[maybe_unused]] cpp2::in<std::string> unnamed_param_1, 
     std::string b, 
-    [[maybe_unused]] std::string& param3, 
+    [[maybe_unused]] std::string& unnamed_param_3, 
     std::string&& d
     ) -> void
 {

regression-tests/test-results/mixed-postfix-expression-custom-formatting.cpp

@@ -11,7 +11,7 @@
 
 
 #line 2 "mixed-postfix-expression-custom-formatting.cpp2"
-auto call([[maybe_unused]] auto const& param1, [[maybe_unused]] auto const& param2, [[maybe_unused]] auto const& param3, [[maybe_unused]] auto const& param4, [[maybe_unused]] auto const& param5) -> void;
+auto call([[maybe_unused]] auto const& unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3, [[maybe_unused]] auto const& unnamed_param_4, [[maybe_unused]] auto const& unnamed_param_5) -> void;
 
 [[nodiscard]] auto test(auto const& a) -> std::string;
 
@@ -24,7 +24,7 @@ auto call([[maybe_unused]] auto const& param1, [[maybe_unused]] auto const& para
 
 
 #line 2 "mixed-postfix-expression-custom-formatting.cpp2"
-auto call([[maybe_unused]] auto const& param1, [[maybe_unused]] auto const& param2, [[maybe_unused]] auto const& param3, [[maybe_unused]] auto const& param4, [[maybe_unused]] auto const& param5) -> void{}
+auto call([[maybe_unused]] auto const& unnamed_param_1, [[maybe_unused]] auto const& unnamed_param_2, [[maybe_unused]] auto const& unnamed_param_3, [[maybe_unused]] auto const& unnamed_param_4, [[maybe_unused]] auto const& unnamed_param_5) -> void{}
 
 [[nodiscard]] auto test(auto const& a) -> std::string{
     return call(a, 

regression-tests/test-results/pure2-bugfix-for-memberwise-base-assignment.cpp

@@ -27,9 +27,9 @@ class Base {
 
 #line 3 "pure2-bugfix-for-memberwise-base-assignment.cpp2"
   public: auto operator=([[maybe_unused]] Base&& that) noexcept -> Base& ;
-  public: Base([[maybe_unused]] auto const& param2);
+  public: Base([[maybe_unused]] auto const& unnamed_param_2);
 #line 4 "pure2-bugfix-for-memberwise-base-assignment.cpp2"
-  public: auto operator=([[maybe_unused]] auto const& param2) -> Base& ;
+  public: auto operator=([[maybe_unused]] auto const& unnamed_param_2) -> Base& ;
 };
 
 class Derived: public Base {
@@ -60,9 +60,9 @@ auto main() -> int;
                                       return *this;
 #line 3 "pure2-bugfix-for-memberwise-base-assignment.cpp2"
                                      }
-  Base::Base([[maybe_unused]] auto const& param2) { std::cout << "(implicit out this, _)\n";  }
+  Base::Base([[maybe_unused]] auto const& unnamed_param_2) { std::cout << "(implicit out this, _)\n";  }
 #line 4 "pure2-bugfix-for-memberwise-base-assignment.cpp2"
-  auto Base::operator=([[maybe_unused]] auto const& param2) -> Base&  { std::cout << "(implicit out this, _)\n";
+  auto Base::operator=([[maybe_unused]] auto const& unnamed_param_2) -> Base&  { std::cout << "(implicit out this, _)\n";
                                       return *this;
 #line 4 "pure2-bugfix-for-memberwise-base-assignment.cpp2"
    }

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

@@ -38,15 +38,15 @@ CPP2_REQUIRES_ (true)
 
 
 #line 54 "pure2-print.cpp2"
-        public: template<typename T> [[nodiscard]] auto values([[maybe_unused]] T const& param2) const& -> values_ret;
+        public: template<typename T> [[nodiscard]] auto values([[maybe_unused]] T const& unnamed_param_2) const& -> values_ret;
 
 
 #line 59 "pure2-print.cpp2"
         public: explicit mytype();
 
         public: mytype([[maybe_unused]] mytype const& that);
 
-        public: mytype([[maybe_unused]] cpp2::in<int> param2);
+        public: mytype([[maybe_unused]] cpp2::in<int> unnamed_param_2);
 
         public: static auto variadic(auto const& ...x) -> void
 CPP2_REQUIRES_ ((std::is_convertible_v<CPP2_TYPEOF(x), int> && ...))
@@ -133,7 +133,7 @@ requires (true)
 
             do {} while ( CPP2_UFCS_0(empty, s) && [&]{ b() ; return true; }() );
 
-            for ( [[maybe_unused]] auto const& param1 : m ) {
+            for ( [[maybe_unused]] auto const& unnamed_param_1 : m ) {
 #line 43 "pure2-print.cpp2"
              { do {goto CONTINUE_43_13; } while (false); c(); } CPP2_CONTINUE_BREAK(43_13) }
 
@@ -147,7 +147,7 @@ requires (true)
             return [_0 = (s + cpp2::assert_in_bounds(m, 0))]() -> std::string { return _0;  }(); 
         }
 
-        template<typename T> [[nodiscard]] auto outer::mytype::values([[maybe_unused]] T const& param2) const& -> values_ret{
+        template<typename T> [[nodiscard]] auto outer::mytype::values([[maybe_unused]] T const& unnamed_param_2) const& -> values_ret{
                 cpp2::deferred_init<int> offset;
                 cpp2::deferred_init<std::string> name;
 #line 55 "pure2-print.cpp2"
@@ -159,7 +159,7 @@ requires (true)
 
         outer::mytype::mytype([[maybe_unused]] mytype const& that){}
 
-        outer::mytype::mytype([[maybe_unused]] cpp2::in<int> param2){}
+        outer::mytype::mytype([[maybe_unused]] cpp2::in<int> unnamed_param_2){}
 
         auto outer::mytype::variadic(auto const& ...x) -> void
 requires ((std::is_convertible_v<CPP2_TYPEOF(x), int> && ...))

regression-tests/test-results/pure2-types-down-upcast.cpp

@@ -37,8 +37,8 @@ class B: public A {
 #line 11 "pure2-types-down-upcast.cpp2"
 };
 
-auto func_mut(A&  a) -> void;
-auto func_mut(B&  b) -> void;
+auto func_mut(A& a) -> void;
+auto func_mut(B& b) -> void;
 auto func_const(cpp2::in<A> a) -> void;
 auto func_const(cpp2::in<B> b) -> void;
 
@@ -69,8 +69,8 @@ auto test_down() -> void;
  auto A::mut_foo() & -> void{std::cout << "foo \n"; }
 
 #line 13 "pure2-types-down-upcast.cpp2"
-auto func_mut(A&  a) -> void    {std::cout << "Call A mut: " + cpp2::to_string(a.i) << std::endl;}
-auto func_mut(B&  b) -> void    {std::cout << "Call B mut: " + cpp2::to_string(b.d) << std::endl;}
+auto func_mut(A& a) -> void     {std::cout << "Call A mut: " + cpp2::to_string(a.i) << std::endl;}
+auto func_mut(B& b) -> void     {std::cout << "Call B mut: " + cpp2::to_string(b.d) << std::endl;}
 auto func_const(cpp2::in<A> a) -> void{std::cout << "Call A const: " + cpp2::to_string(a.i) << std::endl;}
 auto func_const(cpp2::in<B> b) -> void{std::cout << "Call B const: " + cpp2::to_string(b.d) << std::endl;}
 

regression-tests/test-results/pure2-types-inheritance.cpp

@@ -39,7 +39,7 @@ public: virtual ~Human() noexcept;
 
 namespace N {
     template<int I> class Machine {
-        public: explicit Machine([[maybe_unused]] cpp2::in<std::string> param2);
+        public: explicit Machine([[maybe_unused]] cpp2::in<std::string> unnamed_param_2);
         public: virtual auto work() const -> void = 0;
 
     public: virtual ~Machine() noexcept;
@@ -97,7 +97,7 @@ auto main() -> int;
 #line 6 "pure2-types-inheritance.cpp2"
 namespace N {
 
-        template <int I> Machine<I>::Machine([[maybe_unused]] cpp2::in<std::string> param2){}
+        template <int I> Machine<I>::Machine([[maybe_unused]] cpp2::in<std::string> unnamed_param_2){}
 
         template <int I> Machine<I>::~Machine() noexcept{}
 

regression-tests/test-results/pure2-ufcs-member-access-and-chaining.cpp

@@ -14,7 +14,7 @@
 
 
 #line 24 "pure2-ufcs-member-access-and-chaining.cpp2"
-auto no_return([[maybe_unused]] auto const& param1) -> void;
+auto no_return([[maybe_unused]] auto const& unnamed_param_1) -> void;
 
 [[nodiscard]] auto ufcs(cpp2::in<int> i) -> int;
     struct fun_ret { int i; };
@@ -31,7 +31,7 @@ auto no_return([[maybe_unused]] auto const& param1) -> void;
 
 #line 39 "pure2-ufcs-member-access-and-chaining.cpp2"
 //  And a test for non-local UFCS, which shouldn't do a [&] capture
-[[nodiscard]] auto f([[maybe_unused]] auto const& param1) -> int;
+[[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_1) -> int;
 extern int y;
 
 //=== Cpp2 function definitions =================================================
@@ -59,7 +59,7 @@ extern int y;
     CPP2_UFCS_0(no_return, 42);
 }
 
-auto no_return([[maybe_unused]] auto const& param1) -> void{}
+auto no_return([[maybe_unused]] auto const& unnamed_param_1) -> void{}
 
 [[nodiscard]] auto ufcs(cpp2::in<int> i) -> int{
     return i + 2; 
@@ -77,6 +77,6 @@ auto no_return([[maybe_unused]] auto const& param1) -> void{}
 }
 
 #line 40 "pure2-ufcs-member-access-and-chaining.cpp2"
-[[nodiscard]] auto f([[maybe_unused]] auto const& param1) -> int { return 0;  }
+[[nodiscard]] auto f([[maybe_unused]] auto const& unnamed_param_1) -> int { return 0;  }
 int y {CPP2_UFCS_0_NONLOCAL(f, 0)}; 
 

regression-tests/test-results/version

@@ -1,5 +1,5 @@
 
-cppfront compiler v0.3.0   Build 8B07:1638
+cppfront compiler v0.3.0   Build 8B09:1419
 Copyright(c) Herb Sutter   All rights reserved
 
 SPDX-License-Identifier: CC-BY-NC-ND-4.0

source/build.info

@@ -1 +1 @@
-"8B07:1638"
+"8B09:1419"

source/sema.h

@@ -1000,6 +1000,34 @@ class sema
     }
 
 
+    auto check(parameter_declaration_node const& n)
+        -> bool
+    {
+        auto type_name = std::string{};
+        if (n.declaration->has_declared_return_type()) {
+            type_name = n.declaration->get_object_type()->to_string();
+        }
+
+        if (
+            n.ordinal == 2
+            && !n.has_name("that")
+            && n.declaration->parent_declaration
+            && n.declaration->parent_declaration->has_name("operator=")
+            && n.declaration->parent_declaration->parent_declaration
+            && n.declaration->parent_declaration->parent_declaration->name()
+            && type_name == *n.declaration->parent_declaration->parent_declaration->name()
+            )
+        {
+            errors.emplace_back(
+                n.position(),
+                "if an 'operator=' second parameter is of the same type (here '" + type_name + "'), it must be named 'that'"
+            );
+            return false;
+        }
+
+        return true;
+    }
+
     auto check(declaration_node const& n)
         -> bool
     {