fix(to_cpp1): improve recognition of dependent types and deducible parameters

regression-tests/pure2-bugfix-for-deducible-parameters.cpp2

@@ -0,0 +1,32 @@
+// Dependent, non-deducible parameters are wrapped like non-dependent parameters.
+init: <T> (out x: std::integral_constant<i32, T::value>) = { x = (); }
+init: <T> (out x: std::integral_constant<i32, T::value>, _: T) = { x = (); }
+id: <T> (in_ref x: std::integral_constant<i32, T::value>) = x;
+id: <T> (x: std::integral_constant<i32, T::value>, y: T) = { assert(x& == y&); }
+
+main: () = {
+  zero: type == std::integral_constant<i32, 0>;
+
+  z: zero;
+  init<zero>(out z);
+  assert(id<zero>(z)& == z&);
+
+  // Deducible parameters.
+  _ = :v                   = 0;
+  :<T> (_: std::vector<T>) = {}(:std::vector<i32> = ());
+  :<T> (_: std::vector<std::vector<T>>) = {}(:std::vector<std::vector<i32>> = ());
+  // _ = :<T, U> (x: std::pair<T, typename U::value_type>, y: U) = {}(:std::pair = (0, 0), z); // Blocked on #727.
+  :<T, U> (_: std::array<T, U::value>, _: U) = {}(:std::array<i32, 0> = (), z);
+  init(out z, z);
+  id(z, z);
+
+  // Test that these are emitted unwrapped in case they are deducible.
+  (copy f := :<T> (_: std::vector<std::type_identity_t<T>>) = {})
+    static_assert(!std::is_invocable_v<decltype(f), std::vector<i32>>, "`T` is non-deducible.");
+  (copy f := :<T> (_: std::vector<std::vector<T>>) = {})
+    static_assert(std::is_invocable_v<decltype(f), std::vector<std::vector<i32>>>, "`T` is deducible.");
+}
+
+v: <T> type = {
+  operator=: (out this, _: T) = { }
+}

regression-tests/pure2-bugfix-for-dependent-types-recursion.cpp2

@@ -0,0 +1,6 @@
+main: () = {
+  a: type == b;
+  b: type == a;
+  _ = a::t;
+  _ = b::t;
+}

regression-tests/pure2-bugfix-for-dependent-types.cpp2

@@ -0,0 +1,96 @@
+identity: <T> type == T;
+
+f: <T> (inout _: T::value_type) = { }
+f: <T> (move _: T::value_type) = { }
+f: <T, V: T::value_type> (x: T::value_type) -> T::value_type = {
+  assert(x is T::value_type);
+  y: T::value_type;
+  y = x;
+  z: type == T::value_type;
+  return (:T::value_type = x);
+
+  // Dependent *template-id*s.
+  _ = :identity<T>::value_type = ();      // First identifier.
+  _ = :std::optional<T>::value_type = (); // Non-first identifier.
+  _ = :std::array<i32, T::value>::value_type = ();
+  _ = :std::array<i32, T::value + T::value>::value_type = ();
+
+  // Emitted `template`.
+  ptr: type  == * T; // Also test lookup through type aliases.
+  nptr: type == * i32;
+  _ = :std::pointer_traits<ptr>::rebind<ptr> = ();   // Type-only context.
+  _ = :std::pointer_traits<nptr>::rebind<nptr> = (); // Non-dependent.
+  _ = :std::pointer_traits<nptr>::rebind<ptr> = ();  // Dependent on the nested template.
+  _ = :std::pointer_traits<ptr>::rebind<nptr> = ();  // Dependent on the outer template.
+  // _ = :identity<typename std::pointer_traits<ptr>::rebind<ptr>> = (); // Non type-only context. Blocked on #727.
+
+  // Aliases.
+  w: type == T;
+  _ = :w::value_type = x;
+  v: type == w;
+  _ = :v::value_type = x;
+  a: type == T::type;
+  _ = :a::value_type = x;
+
+  {
+    // Test that there's no prefixed `typename` to....
+    _ = std::integral_constant<i32, T::value>(); // `T::value`.
+    _ = :std::type_identity_t<T> = ();           // `std::type_identity_t<T>`.
+
+    // Test that non-dependent names aren't emitted with `typename`.
+    a: type == std::integral_constant<i32, 0>;
+    b: type == a;
+    c: type == b;
+    _ = :b::value_type = x;
+    _ = :c::value_type = x;
+  }
+}
+
+t: @cpp1_rule_of_zero <T: type> type = {
+  u: type = {
+    x: T::value_type = ();
+    this: T::type    = ();
+    // Test that there's no `typename` in the member initializer list.
+    operator=: (out this, that) = { }
+  }
+  x: T::value_type = 0;
+}
+
+main: () = {
+  zero: type == std::integral_constant<i32, 0>;
+  _ = f<zero, 0>(0);
+
+  _ = : ::t<zero> = ();
+
+  // Emitted `template` (noop, taken care of by the UFCS macro).
+  _ = :(move f) = _ = f.operator()<i32>();(:<T> () = {});
+
+  // Nesting is not relevant to lookup.
+  _ = :<T> () = { _ = :T::value_type = (); };
+  _ = :() = { _ = :<T> () = { _ = :T::value_type = (); }; };
+  _ = :() = { _ = :() = { _ = :<T> () = { _ = :T::value_type = (); }; }; };
+  _ = :() = { _ = :() = { _ = :() = { _ = :<T> () = { _ = :T::value_type = (); }; }; }; };
+  _ = :() = { _ = :() = { _ = :<T> () = { _ = :() = { _ = :T::value_type = (); }; }; }; };
+  _ = :() = { _ = :<T> () = { _ = :() = { _ = :() = { _ = :T::value_type = (); }; }; }; };
+  _ = :<T> () = { _ = :() = { _ = :() = { _ = :() = { _ = :T::value_type = (); }; }; }; };
+  _ = :<T> () = { _ = :() = { _ = :() = { _ = :(_: T::value_type) = {}; }; }; };
+  _ = :<T> () = { _ = :() = { _ = :(_: T::value_type) = { _ = :() = {}; }; }; };
+  _ = :<T> () = { _ = :(_: T::value_type) = { _ = :() = { _ = :() = {}; }; }; };
+  _ = :<T> (_: T::value_type) = { _ = :() = { _ = :() = { _ = :() = {}; }; }; };
+
+  // Lookup.
+  {
+    alias: type == std::integral_constant<i32, 0>;
+    _ = :alias::value_type = 0; // Non-dependent.
+  }
+  _ = :<T> (_: T) = {
+    alias: type == std::integral_constant<T, 0>;
+    _ = :alias::value_type = 0; // Dependent.
+    {
+      alias: type == std::integral_constant<i32, 0>;
+      _ = :alias::value_type = 0; // Non-dependent.
+    }
+  }(0);
+
+  _ = :(r) -> std::type_identity_t<decltype(begin(r)*)> = r[0];(std::vector<int>(1));
+}

regression-tests/test-results/clang-12-c++20/pure2-bugfix-for-dependent-types-recursion.cpp.output

@@ -0,0 +1,13 @@
+pure2-bugfix-for-dependent-types-recursion.cpp2:2:13: error: unknown type name 'b'
+  using a = b;
+            ^
+pure2-bugfix-for-dependent-types-recursion.cpp2:3:13: error: unknown type name 'a'
+  using b = a;
+            ^
+pure2-bugfix-for-dependent-types-recursion.cpp2:4:21: error: use of undeclared identifier 'a'
+  static_cast<void>(a::t);
+                    ^
+pure2-bugfix-for-dependent-types-recursion.cpp2:5:21: error: use of undeclared identifier 'b'
+  static_cast<void>(b::t);
+                    ^
+4 errors generated.

regression-tests/test-results/clang-12-c++20/pure2-bugfix-for-dependent-types.cpp.output

@@ -0,0 +1,29 @@
+pure2-bugfix-for-dependent-types.cpp2:5:22: error: missing 'typename' prior to dependent type name 'T::value_type'
+template<typename T, T::value_type V> [[nodiscard]] auto f(cpp2::impl::in<typename T::value_type> x) -> T::value_type;
+                     ^~~~~~~~~~~~~
+                     typename 
+pure2-bugfix-for-dependent-types.cpp2:5:105: error: missing 'typename' prior to dependent type name 'T::value_type'
+template<typename T, T::value_type V> [[nodiscard]] auto f(cpp2::impl::in<typename T::value_type> x) -> T::value_type;
+                                                                                                        ^~~~~~~~~~~~~
+                                                                                                        typename 
+pure2-bugfix-for-dependent-types.cpp2:56:12: error: missing 'typename' prior to dependent type name 'T::value_type'
+  private: T::value_type x {0}; 
+           ^~~~~~~~~~~~~
+           typename 
+pure2-bugfix-for-dependent-types.cpp2:5:22: error: missing 'typename' prior to dependent type name 'T::value_type'
+template<typename T, T::value_type V> [[nodiscard]] auto f(cpp2::impl::in<typename T::value_type> x) -> T::value_type{
+                     ^~~~~~~~~~~~~
+                     typename 
+pure2-bugfix-for-dependent-types.cpp2:5:105: error: missing 'typename' prior to dependent type name 'T::value_type'
+template<typename T, T::value_type V> [[nodiscard]] auto f(cpp2::impl::in<typename T::value_type> x) -> T::value_type{
+                                                                                                        ^~~~~~~~~~~~~
+                                                                                                        typename 
+pure2-bugfix-for-dependent-types.cpp2:9:13: error: missing 'typename' prior to dependent type name 'T::value_type'
+  using z = T::value_type;
+            ^~~~~~~~~~~~~
+            typename 
+pure2-bugfix-for-dependent-types.cpp2:32:13: error: missing 'typename' prior to dependent type name 'T::type'
+  using a = T::type;
+            ^~~~~~~
+            typename 
+7 errors generated.

regression-tests/test-results/gcc-10-c++20/pure2-bugfix-for-dependent-types-recursion.cpp.output

@@ -0,0 +1,5 @@
+pure2-bugfix-for-dependent-types-recursion.cpp2: In function ‘int main()’:
+pure2-bugfix-for-dependent-types-recursion.cpp2:2:13: error: ‘b’ does not name a type
+pure2-bugfix-for-dependent-types-recursion.cpp2:3:13: error: ‘a’ does not name a type
+pure2-bugfix-for-dependent-types-recursion.cpp2:4:21: error: ‘a’ has not been declared
+pure2-bugfix-for-dependent-types-recursion.cpp2:5:21: error: ‘b’ has not been declared

regression-tests/test-results/gcc-10-c++20/pure2-bugfix-for-dependent-types.cpp.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-dependent-types.cpp2: In function ‘typename T::value_type f(cpp2::impl::in<typename T::value_type>) [with T = std::integral_constant<int, 0>; typename T::value_type V = 0]’:
+pure2-bugfix-for-dependent-types.cpp2:47:1: warning: control reaches end of non-void function [-Wreturn-type]

regression-tests/test-results/gcc-14-c++2b/pure2-bugfix-for-dependent-types-recursion.cpp.output

@@ -0,0 +1,5 @@
+pure2-bugfix-for-dependent-types-recursion.cpp2: In function ‘int main()’:
+pure2-bugfix-for-dependent-types-recursion.cpp2:2:13: error: ‘b’ does not name a type
+pure2-bugfix-for-dependent-types-recursion.cpp2:3:13: error: ‘a’ does not name a type
+pure2-bugfix-for-dependent-types-recursion.cpp2:4:21: error: ‘a’ has not been declared
+pure2-bugfix-for-dependent-types-recursion.cpp2:5:21: error: ‘b’ has not been declared

regression-tests/test-results/msvc-2022-c++latest/pure2-bugfix-for-deducible-parameters.cpp.output

@@ -0,0 +1 @@
+pure2-bugfix-for-deducible-parameters.cpp

regression-tests/test-results/msvc-2022-c++latest/pure2-bugfix-for-dependent-types-recursion.cpp.output

@@ -0,0 +1,7 @@
+pure2-bugfix-for-dependent-types-recursion.cpp
+pure2-bugfix-for-dependent-types-recursion.cpp2(2): error C2061: syntax error: identifier 'b'
+pure2-bugfix-for-dependent-types-recursion.cpp2(3): error C2061: syntax error: identifier 'a'
+pure2-bugfix-for-dependent-types-recursion.cpp2(4): error C2653: 'a': is not a class or namespace name
+pure2-bugfix-for-dependent-types-recursion.cpp2(4): error C2065: 't': undeclared identifier
+pure2-bugfix-for-dependent-types-recursion.cpp2(5): error C2653: 'b': is not a class or namespace name
+pure2-bugfix-for-dependent-types-recursion.cpp2(5): error C2065: 't': undeclared identifier

regression-tests/test-results/msvc-2022-c++latest/pure2-bugfix-for-dependent-types.cpp.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-dependent-types.cpp
+pure2-bugfix-for-dependent-types.cpp2(66): fatal error C1202: recursive type or function dependency context too complex

regression-tests/test-results/pure2-bugfix-for-deducible-parameters.cpp

@@ -0,0 +1,90 @@
+
+#define CPP2_IMPORT_STD          Yes
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+#line 1 "pure2-bugfix-for-deducible-parameters.cpp2"
+
+#line 30 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> class v;
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+#line 1 "pure2-bugfix-for-deducible-parameters.cpp2"
+// Dependent, non-deducible parameters are wrapped like non-dependent parameters.
+#line 2 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> auto init(cpp2::impl::out<std::integral_constant<cpp2::i32,T::value>> x) -> void;
+template<typename T> auto init(cpp2::impl::out<std::integral_constant<cpp2::i32,T::value>> x, [[maybe_unused]] T const& unnamed_param_2) -> void;
+template<typename T> [[nodiscard]] auto id(std::integral_constant<cpp2::i32,T::value> const& x) -> decltype(auto);
+template<typename T> auto id(cpp2::impl::in<std::integral_constant<cpp2::i32,T::value>> x, T const& y) -> void;
+
+auto main() -> int;
+
+#line 30 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> class v {
+  public: explicit v([[maybe_unused]] T const& unnamed_param_2);
+#line 31 "pure2-bugfix-for-deducible-parameters.cpp2"
+  public: auto operator=([[maybe_unused]] T const& unnamed_param_2) -> v& ;
+  public: v(v const&) = delete; /* No 'that' constructor, suppress copy */
+  public: auto operator=(v const&) -> void = delete;
+
+#line 32 "pure2-bugfix-for-deducible-parameters.cpp2"
+};
+
+
+//=== Cpp2 function definitions =================================================
+
+#line 1 "pure2-bugfix-for-deducible-parameters.cpp2"
+
+#line 2 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> auto init(cpp2::impl::out<std::integral_constant<cpp2::i32,T::value>> x) -> void{x.construct(); }
+#line 3 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> auto init(cpp2::impl::out<std::integral_constant<cpp2::i32,T::value>> x, [[maybe_unused]] T const& unnamed_param_2) -> void{x.construct(); }
+#line 4 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> [[nodiscard]] auto id(std::integral_constant<cpp2::i32,T::value> const& x) -> decltype(auto) { return x;  }
+#line 5 "pure2-bugfix-for-deducible-parameters.cpp2"
+template<typename T> auto id(cpp2::impl::in<std::integral_constant<cpp2::i32,T::value>> x, T const& y) -> void{if (cpp2::cpp2_default.is_active() && !(&x == &y) ) { cpp2::cpp2_default.report_violation(""); }}
+
+#line 7 "pure2-bugfix-for-deducible-parameters.cpp2"
+auto main() -> int{
+  using zero = std::integral_constant<cpp2::i32,0>;
+
+  cpp2::impl::deferred_init<zero> z; 
+  init<zero>(cpp2::impl::out(&z));
+  if (cpp2::cpp2_default.is_active() && !(&id<zero>(z.value()) == &z.value()) ) { cpp2::cpp2_default.report_violation(""); }
+
+  // Deducible parameters.
+  static_cast<void>(v{  0});
+  []<typename T>([[maybe_unused]] std::vector<T> const& unnamed_param_1) -> void{}(std::vector<cpp2::i32>{});
+  []<typename T>([[maybe_unused]] std::vector<std::vector<T>> const& unnamed_param_1) -> void{}(std::vector<std::vector<cpp2::i32>>{});
+  // _ = :<T, U> (x: std::pair<T, typename U::value_type>, y: U) = {}(:std::pair = (0, 0), z); // Blocked on #727.
+  []<typename T, typename U>([[maybe_unused]] std::array<T,U::value> const& unnamed_param_1, [[maybe_unused]] U const& unnamed_param_2) -> void{}(std::array<cpp2::i32,0>{}, z.value());
+  init(cpp2::impl::out(&z.value()), z.value());
+  id(z.value(), cpp2::move(z.value()));
+{
+auto f{[]<typename T>([[maybe_unused]] std::vector<std::type_identity_t<T>> const& unnamed_param_1) -> void{}};
+
+  // Test that these are emitted unwrapped in case they are deducible.
+
+#line 25 "pure2-bugfix-for-deducible-parameters.cpp2"
+    static_assert(!(std::is_invocable_v<decltype(cpp2::move(f)),std::vector<cpp2::i32>>), "`T` is non-deducible.");
+}
+{
+auto f{[]<typename T>([[maybe_unused]] std::vector<std::vector<T>> const& unnamed_param_1) -> void{}};
+
+#line 27 "pure2-bugfix-for-deducible-parameters.cpp2"
+    static_assert(std::is_invocable_v<decltype(cpp2::move(f)),std::vector<std::vector<cpp2::i32>>>, "`T` is deducible.");
+}
+#line 28 "pure2-bugfix-for-deducible-parameters.cpp2"
+}
+
+#line 31 "pure2-bugfix-for-deducible-parameters.cpp2"
+  template <typename T> v<T>::v([[maybe_unused]] T const& unnamed_param_2){}
+#line 31 "pure2-bugfix-for-deducible-parameters.cpp2"
+  template <typename T> auto v<T>::operator=([[maybe_unused]] T const& unnamed_param_2) -> v& {
+                                  return *this; }
+

regression-tests/test-results/pure2-bugfix-for-deducible-parameters.cpp2.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-deducible-parameters.cpp2... ok (all Cpp2, passes safety checks)
+

regression-tests/test-results/pure2-bugfix-for-dependent-types-recursion.cpp

@@ -0,0 +1,27 @@
+
+#define CPP2_IMPORT_STD          Yes
+
+//=== Cpp2 type declarations ====================================================
+
+
+#include "cpp2util.h"
+
+#line 1 "pure2-bugfix-for-dependent-types-recursion.cpp2"
+
+
+//=== Cpp2 type definitions and function declarations ===========================
+
+#line 1 "pure2-bugfix-for-dependent-types-recursion.cpp2"
+auto main() -> int;
+
+//=== Cpp2 function definitions =================================================
+
+#line 1 "pure2-bugfix-for-dependent-types-recursion.cpp2"
+auto main() -> int{
+#line 2 "pure2-bugfix-for-dependent-types-recursion.cpp2"
+  using a = b;
+  using b = a;
+  static_cast<void>(a::t);
+  static_cast<void>(b::t);
+}
+

regression-tests/test-results/pure2-bugfix-for-dependent-types-recursion.cpp2.output

@@ -0,0 +1,2 @@
+pure2-bugfix-for-dependent-types-recursion.cpp2... ok (all Cpp2, passes safety checks)
+