Add MoveOnlyFunction implementation and remove uses of shared_ptr

PromptCallback used to be std::function which needed copy support,
preventing move-only lambda which led to the use of shared_ptr to
store ScopedSelectionEdition.

Author: mawww

src/function.hh

@@ -23,10 +23,10 @@ inline constexpr FunctionVTable<Res, Args...> unset_vtable{
     .destroy = [](void*) {},
 };
 
-template<typename Target, typename Res, typename... Args>
+template<bool Copyable, typename Target, typename Res, typename... Args>
 inline constexpr FunctionVTable<Res, Args...> vtable_for{
     .call = [](void* target, Args... args) -> Res { return (*reinterpret_cast<Target*>(target))(std::forward<Args>(args)...); },
-    .clone = [](void* target) -> void* { return new Target(*reinterpret_cast<Target*>(target)); },
+    .clone = [](void* target) -> void* { if constexpr (Copyable) { return new Target(*reinterpret_cast<Target*>(target)); } return nullptr; },
     .destroy = [](void* target) { delete reinterpret_cast<Target*>(target); }
 };
 
@@ -37,18 +37,18 @@ inline constexpr FunctionVTable<Res, Args...> vtable_for_func{
     .destroy = [](void* target) {}
 };
 
-template<typename F>
-class Function;
+template<bool Copyable, typename F>
+class FunctionImpl;
 
-template<typename Res, typename... Args>
-class Function<Res (Args...)>
+template<bool Copyable, typename Res, typename... Args>
+class FunctionImpl<Copyable, Res (Args...)>
 {
 public:
-    Function() = default;
+    FunctionImpl() = default;
 
     template<typename Target>
-        requires (not std::is_same_v<Function, std::remove_cvref_t<Target>>)
-    Function(Target&& target)
+        requires (not std::is_same_v<FunctionImpl, std::remove_cvref_t<Target>>)
+    FunctionImpl(Target&& target)
     {
         using EffectiveTarget = std::remove_cvref_t<Target>;
         if constexpr (std::is_convertible_v<EffectiveTarget, Res(*)(Args...)>)
@@ -59,33 +59,34 @@ public:
         else
         {
             m_target = new EffectiveTarget(std::forward<Target>(target));
-            m_vtable = &vtable_for<EffectiveTarget, Res, Args...>;
+            m_vtable = &vtable_for<Copyable, EffectiveTarget, Res, Args...>;
         }
     }
 
-    Function(const Function& other) : m_target(other.m_vtable->clone(other.m_target)), m_vtable(other.m_vtable)
+    FunctionImpl(const FunctionImpl& other) requires Copyable
+        : m_target(other.m_vtable->clone(other.m_target)), m_vtable(other.m_vtable)
     {
     }
 
-    Function(Function&& other) : m_target(other.m_target), m_vtable(other.m_vtable)
+    FunctionImpl(FunctionImpl&& other) : m_target(other.m_target), m_vtable(other.m_vtable)
     {
         other.m_target = nullptr;
         other.m_vtable = &unset_vtable<Res, Args...>;
     }
 
-    ~Function()
+    ~FunctionImpl()
     {
         m_vtable->destroy(m_target);
     }
 
-    Function& operator=(const Function& other)
+    FunctionImpl& operator=(const FunctionImpl& other) requires Copyable
     {
         m_target = other.m_vtable->clone(other.m_target);
         m_vtable = other.m_vtable;
         return *this;
     }
 
-    Function& operator=(Function&& other)
+    FunctionImpl& operator=(FunctionImpl&& other)
     {
         m_target = other.m_target;
         m_vtable = other.m_vtable;
@@ -106,6 +107,12 @@ private:
     const FunctionVTable<Res, Args...>* m_vtable = &unset_vtable<Res, Args...>;
 };
 
+template<typename F>
+using Function = FunctionImpl<true, F>;
+
+template<typename F>
+using MoveOnlyFunction = FunctionImpl<false, F>;
+
 }
 
 #endif // function_hh_INCLUDED

src/input_handler.hh

@@ -25,7 +25,7 @@ enum class PromptEvent
     Abort,
     Validate
 };
-using PromptCallback = Function<void (StringView, PromptEvent, Context&)>;
+using PromptCallback = MoveOnlyFunction<void (StringView, PromptEvent, Context&)>;
 
 enum class PromptFlags
 {

src/normal.cc

@@ -28,8 +28,6 @@
 #include "window.hh"
 #include "word_db.hh"
 
-#include <memory>
-
 namespace Kakoune
 {
 
@@ -665,7 +663,7 @@ void pipe(Context& context, NormalParams params)
         prompt, {}, default_command, context.faces()["Prompt"],
         PromptFlags::DropHistoryEntriesWithBlankPrefix, '|',
         shell_complete,
-        [default_command, selection_edition=std::make_shared<ScopedSelectionEdition>(context)]
+        [default_command, selection_edition=ScopedSelectionEdition(context)]
         (StringView cmdline, PromptEvent event, Context& context)
         {
             if (event != PromptEvent::Validate)
@@ -880,7 +878,7 @@ void insert_output(Context& context, NormalParams params)
         prompt, {}, default_command, context.faces()["Prompt"],
         PromptFlags::DropHistoryEntriesWithBlankPrefix, '|',
         shell_complete,
-        [default_command, selection_edition=std::make_shared<ScopedSelectionEdition>(context)]
+        [default_command, selection_edition=ScopedSelectionEdition(context)]
         (StringView cmdline, PromptEvent event, Context& context)
         {
             if (event != PromptEvent::Validate)
@@ -954,7 +952,7 @@ void regex_prompt(Context& context, String prompt, char reg, RegexMode mode, Fun
             return {(int)(word.begin() - regex.begin()), pos,  std::move(candidates) };
         },
         [=, func=std::move(func), saved_reg=RegisterManager::instance()[reg].save(context),
-         selection_edition=std::make_shared<ScopedSelectionEdition>(context)]
+         selection_edition=ScopedSelectionEdition(context)]
         (StringView str, PromptEvent event, Context& context) mutable {
             try
             {
@@ -1247,7 +1245,7 @@ void keep(Context& context, NormalParams params)
     const char reg = to_lower(params.reg ? params.reg : '/');
 
     regex_prompt(context, prompt.str(), reg, RegexMode::Forward,
-                 [selection_edition=std::make_shared<ScopedSelectionEdition>(context)]
+                 [selection_edition=ScopedSelectionEdition(context)]
                  (const Regex& regex, PromptEvent event, Context& context) {
         if (regex.empty() or regex.str().empty())
             return;
@@ -1278,7 +1276,7 @@ void keep_pipe(Context& context, NormalParams params)
     context.input_handler().prompt(
         "keep pipe:", {}, default_command, context.faces()["Prompt"],
         PromptFlags::DropHistoryEntriesWithBlankPrefix, '|', shell_complete,
-        [default_command, selection_edition=std::make_shared<ScopedSelectionEdition>(context)]
+        [default_command, selection_edition=ScopedSelectionEdition(context)]
         (StringView cmdline, PromptEvent event, Context& context) {
             if (event != PromptEvent::Validate)
                 return;