fix(cpp1): emit template for dependent _template-id_

Author: JohelEGP

regression-tests/pure2-optional-typename.cpp2

@@ -10,6 +10,11 @@ f: <T, V: T::value_type> (x: T::value_type) -> T::value_type = {
   _ = :identity<T>::value_type = ();      // First identifier.
   _ = :std::optional<T>::value_type = (); // Non-first identifier.
 
+  // Emitted `template`.
+  ptr: type  == * T;                                   // Needed, pending #502.
+  type: type == std::pointer_traits<ptr>::rebind<ptr>; // Type-only context.
+  _ = :std::pointer_traits<ptr>::rebind<ptr> = ();     // Non type-only context.
+
   // Aliases.
   w: type == T;
   _ = :w::value_type = x;

regression-tests/test-results/pure2-optional-typename.cpp

@@ -15,7 +15,7 @@ template<typename T> using identity = T;
 template<typename T, typename T::value_type V> [[nodiscard]] auto f(cpp2::in<typename T::value_type> x) -> typename T::value_type;
 
 
-#line 31 "pure2-optional-typename.cpp2"
+#line 36 "pure2-optional-typename.cpp2"
 auto main() -> int;
 
 
@@ -34,6 +34,11 @@ template<typename T, typename T::value_type V> [[nodiscard]] auto f(cpp2::in<typ
   (void) typename identity<T>::value_type{};// First identifier.
   (void) typename std::optional<T>::value_type{};// Non-first identifier.
 
+  // Emitted `template`.
+  using ptr = T*;                                      // Needed, pending #502.
+  using type = typename std::pointer_traits<ptr>::template rebind<ptr>;// Type-only context.
+  (void) typename std::pointer_traits<ptr>::template rebind<ptr>{};// Non type-only context.
+
   // Aliases.
   using w = T;
   (void) typename w::value_type{x};

source/cppfront.cpp

@@ -1614,7 +1614,8 @@ class cppfront
         unqualified_id_node const& n,
         bool in_synthesized_multi_return = false,
         bool is_local_name = true,
-        bool is_qualified = false
+        bool is_qualified = false,
+        bool can_emit_template_keyword = false
     )
         -> void
     {
@@ -1663,6 +1664,10 @@ class cppfront
             printer.print_cpp2("CPP2_FORWARD(", {n.position().lineno, n.position().colno - 8});
         }
 
+        if (can_emit_template_keyword && n.open_angle != source_position{}) {
+            printer.print_cpp2("template ", n.position());
+        }
+
         assert(n.identifier);
         emit(*n.identifier, is_qualified);  // inform the identifier if we know this is qualified
 
@@ -1755,7 +1760,7 @@ class cppfront
         auto guard = finally([&]{ looking_up.pop_back(); });
 
         // If any parent declaration
-        return std::any_of(current_declarations.begin() + 1, current_declarations.end(), [&](declaration_node const* decl) {
+        return std::any_of(current_declarations.rbegin(), current_declarations.rend() - 1, [&](declaration_node const* decl) {
             // that can have aliases
             if ((decl->is_function()
                  || decl->is_type()
@@ -1765,7 +1770,7 @@ class cppfront
             {
                 auto& stmts = decl->initializer->get_if<compound_statement_node>()->statements;
                 // among its statements
-                return std::any_of(stmts.begin(), stmts.end(), [&](decltype(stmts.front())& stmt) {
+                return std::any_of(stmts.rbegin(), stmts.rend(), [&](decltype(stmts.front())& stmt) {
                     if (auto decl = stmt->get_if<declaration_node>();
                         decl
                         && decl->is_alias()) {
@@ -1886,12 +1891,16 @@ class cppfront
             printer.print_cpp2("typename ", n.position());
         }
 
+        auto can_emit_template_keyword = false;
         for (auto const& id : n.ids)
         {
             if (id.scope_op) {
                 emit(*id.scope_op);
             }
-            emit(*id.id, false, true, true);    // inform the unqualified-id that it's qualified
+            emit(*id.id, false, true, true, can_emit_template_keyword);    // inform the unqualified-id that it's qualified
+            if (!can_emit_template_keyword && this->is_dependent(*id.id)) {
+                can_emit_template_keyword = true;
+            }
         }
 
         printer.emit_to_string();