[BUG] Recognize non-deducible parameter #534

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1. JohelEGP

   added

   bugSomething isn't workingSomething isn't working

   on Jul 3, 2023
2. JohelEGP

   changed the title [-][BUG] Use `cpp2::in` for non-deducible parameters[/-] [+][BUG] Recognize non-deducible parameter[/+] on Jul 3, 2023
3. JohelEGP commented on Jul 3, 2023

   

   JohelEGP

   on Jul 3, 2023

   ContributorAuthor

   More actions

   Title: Recognize non-deducible parameter.

   Description:

   The report generalizes.
   The same applies to out parameters.

   Minimal reproducer (https://cpp2.godbolt.org/z/Tnvczs8qa):

   f: <T> (out x: std::integral_constant<i32, T::value>) = { x = (); }
   main: () = {
     t: type == std::integral_constant<i32, 0>;
     i: t;
     f<t>(out i);
   }
   

   Commands:

   cppfront main.cpp2
   clang++17 -std=c++23 -stdlib=libc++ -lc++abi -pedantic-errors -Wall -Wextra -Wconversion -I . main.cpp

   Expected result:

   template<typename T> auto f(cpp2::out<std::integral_constant<cpp2::i32, T::value>> x) -> void;

   Actual result and error:

   template<typename T> auto f(std::integral_constant<cpp2::i32,T::value> x_) -> void;

   Cpp2 lowered to Cpp1:

   //=== Cpp2 type declarations ====================================================
   
   
   #include "cpp2util.h"
   
   
   
   //=== Cpp2 type definitions and function declarations ===========================
   
   template<typename T> auto f(std::integral_constant<cpp2::i32,T::value> x_) -> void;
   auto main() -> int;
     
   
   //=== Cpp2 function definitions =================================================
   
   template<typename T> auto f(std::integral_constant<cpp2::i32,T::value> x_) -> void{
                                                             auto x = cpp2::out(x_); 
   x.construct(); }
   auto main() -> int{
     using t = std::integral_constant<cpp2::i32,0>;
     cpp2::deferred_init<t> i; 
     f<t>(cpp2::out(&i));
   }

   Output:

   main.cpp2:5:3: error: no matching function for call to 'f'
       5 |   f<t>(cpp2::out(&i));
         |   ^~~~
   main.cpp2:1:27: note: candidate function template not viable: no known conversion from 'cpp2::out<integral_constant<int, 0>>' (aka 'cpp2::out<std::integral_constant<int, 0>>') to 'std::integral_constant<cpp2::i32, t::value>' (aka 'integral_constant<int, t::value>') for 1st argument
       5 | template<typename T> auto f(std::integral_constant<cpp2::i32,T::value> x_) -> void{
         |                           ^
       6 |                                                           auto x = cpp2::out(x_); 
       7 | #line 1 "/app/main.cpp2"
       8 | x.construct(); }
       9 | auto main() -> int{
      10 |   using t = std::integral_constant<cpp2::i32,0>;
      11 |   cpp2::deferred_init<t> i; 
      12 |   f<t>(cpp2::out(&i));
         |        ~~~~~~~~~~~~~
   1 error generated.
   
4. JohelEGP commented on Jul 6, 2023

   

   JohelEGP

   on Jul 6, 2023

   ContributorAuthor

   More actions

   See #533 (comment) for the source of the bug.