From 91550639bbbd20c92957b83abfbb3ec4c43b3ab4 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Sun, 21 Nov 2021 11:15:08 +1100
Subject: [PATCH] More C++20 refactorings

Use CTAD instead of make functions, requires instead of enable_if
---
 src/command_manager.cc |  5 +++--
 src/keys.hh            |  2 +-
 src/ranges.hh          | 51 +++++++++++++++++++++---------------------
 src/string_utils.hh    |  4 ++--
 src/utils.hh           | 10 ++++-----
 5 files changed, 36 insertions(+), 36 deletions(-)

diff --git a/src/command_manager.cc b/src/command_manager.cc
index 2c067978..a8212d06 100644
--- a/src/command_manager.cc
+++ b/src/command_manager.cc
@@ -297,14 +297,15 @@ Token parse_percent_token(ParseState& state, bool throw_on_unterminated)
     }
 }
 
-template<typename Target, typename = std::enable_if_t<std::is_same_v<Target, Vector<String>> or std::is_same_v<Target, String>>>
+template<typename Target>
+    requires (std::is_same_v<Target, Vector<String>> or std::is_same_v<Target, String>)
 void expand_token(Token&& token, const Context& context, const ShellContext& shell_context, Target& target)
 {
     constexpr bool single = std::is_same_v<Target, String>;
     auto set_target = [&](auto&& s) {
         if constexpr (single)
             target = std::move(s);
-        else if constexpr (std::is_same_v<std::decay_t<decltype(s)>, String>)
+        else if constexpr (std::is_same_v<std::remove_cvref_t<decltype(s)>, String>)
             target.push_back(std::move(s));
         else if constexpr (std::is_same_v<decltype(s), Vector<String>&&>)
             target.insert(target.end(), std::make_move_iterator(s.begin()), std::make_move_iterator(s.end()));
diff --git a/src/keys.hh b/src/keys.hh
index f06a7e2f..da2895e7 100644
--- a/src/keys.hh
+++ b/src/keys.hh
@@ -84,7 +84,7 @@ struct Key
     constexpr uint64_t val() const { return (uint64_t)modifiers << 32 | key; }
 
     constexpr bool operator==(Key other) const { return val() == other.val(); }
-    constexpr bool operator<(Key other) const { return val() < other.val(); }
+    constexpr std::strong_ordering operator<=>(Key other) const { return val() <=> other.val(); }
 
     constexpr DisplayCoord coord() const { return {(int)((key & 0xFFFF0000) >> 16), (int)(key & 0x0000FFFF)}; }
     constexpr MouseButton mouse_button() { return MouseButton{((int)modifiers & (int)Modifiers::MouseButtonMask) >> 6}; }
diff --git a/src/ranges.hh b/src/ranges.hh
index 5fb1e2c9..cf436880 100644
--- a/src/ranges.hh
+++ b/src/ranges.hh
@@ -15,8 +15,7 @@ namespace Kakoune
 template<typename Func> struct ViewFactory { Func func; };
 
 template<typename Func>
-ViewFactory<std::remove_cvref_t<Func>>
-make_view_factory(Func&& func) { return {std::forward<Func>(func)}; }
+ViewFactory(Func&&) -> ViewFactory<std::remove_cvref_t<Func>>;
 
 template<typename Range, typename Func>
 decltype(auto) operator| (Range&& range, ViewFactory<Func> factory)
@@ -50,10 +49,10 @@ struct ReverseView
 
 inline auto reverse()
 {
-    return make_view_factory([](auto&& range) {
+    return ViewFactory{[](auto&& range) {
         using Range = decltype(range);
         return ReverseView<decay_range<Range>>{std::forward<Range>(range)};
-    });
+    }};
 }
 
 template<typename Range>
@@ -74,10 +73,10 @@ struct SkipView
 
 inline auto skip(size_t count)
 {
-    return make_view_factory([count](auto&& range) {
+    return ViewFactory{[count](auto&& range) {
         using Range = decltype(range);
         return SkipView<decay_range<Range>>{std::forward<Range>(range), count};
-    });
+    }};
 }
 
 template<typename Range>
@@ -92,10 +91,10 @@ struct DropView
 
 inline auto drop(size_t count)
 {
-    return make_view_factory([count](auto&& range) {
+    return ViewFactory{[count](auto&& range) {
         using Range = decltype(range);
         return DropView<decay_range<Range>>{std::forward<Range>(range), count};
-    });
+    }};
 }
 
 template<typename Range, typename Filter>
@@ -150,10 +149,10 @@ struct FilterView
 template<typename Filter>
 inline auto filter(Filter f)
 {
-    return make_view_factory([f = std::move(f)](auto&& range) {
+    return ViewFactory{[f = std::move(f)](auto&& range) {
         using Range = decltype(range);
         return FilterView<decay_range<Range>, Filter>{std::forward<Range>(range), std::move(f)};
-    });
+    }};
 }
 
 template<typename Range>
@@ -196,10 +195,10 @@ struct EnumerateView
 
 inline auto enumerate()
 {
-    return make_view_factory([](auto&& range) {
+    return ViewFactory{[](auto&& range) {
         using Range = decltype(range);
         return EnumerateView<decay_range<Range>>{std::forward<Range>(range)};
-    });
+    }};
 }
 
 template<typename Range, typename Transform>
@@ -255,10 +254,10 @@ struct TransformView
 template<typename Transform>
 inline auto transform(Transform t)
 {
-    return make_view_factory([t = std::move(t)](auto&& range) {
+    return ViewFactory{[t = std::move(t)](auto&& range) {
         using Range = decltype(range);
         return TransformView<decay_range<Range>, Transform>{std::forward<Range>(range), std::move(t)};
-    });
+    }};
 }
 
 template<typename T, typename U>
@@ -363,28 +362,28 @@ struct SplitView
 template<typename ValueType = void, typename Element>
 auto split(Element separator)
 {
-    return make_view_factory([s = std::move(separator)](auto&& range) {
+    return ViewFactory{[s = std::move(separator)](auto&& range) {
         using Range = decltype(range);
         return SplitView<decay_range<Range>, false, false, Element, ValueType>{std::forward<Range>(range), std::move(s), {}};
-    });
+    }};
 }
 
 template<typename ValueType = void, typename Element>
 auto split_after(Element separator)
 {
-    return make_view_factory([s = std::move(separator)](auto&& range) {
+    return ViewFactory{[s = std::move(separator)](auto&& range) {
         using Range = decltype(range);
         return SplitView<decay_range<Range>, false, true, Element, ValueType>{std::forward<Range>(range), std::move(s), {}};
-    });
+    }};
 }
 
 template<typename ValueType = void, typename Element>
 auto split(Element separator, Element escaper)
 {
-    return make_view_factory([s = std::move(separator), e = std::move(escaper)](auto&& range) {
+    return ViewFactory{[s = std::move(separator), e = std::move(escaper)](auto&& range) {
         using Range = decltype(range);
         return SplitView<decay_range<Range>, true, false, Element, ValueType>{std::forward<Range>(range), std::move(s), std::move(e)};
-    });
+    }};
 }
 
 template<typename Range1, typename Range2>
@@ -518,26 +517,26 @@ void for_n_best(Range&& c, size_t count, Compare&& compare, Func&& func)
 template<typename Container>
 auto gather()
 {
-    return make_view_factory([](auto&& range) {
+    return ViewFactory{[](auto&& range) {
         using std::begin; using std::end;
         return Container(begin(range), end(range));
-    });
+    }};
 }
 
 template<template <typename Element> class Container>
 auto gather()
 {
-    return make_view_factory([](auto&& range) {
+    return ViewFactory{[](auto&& range) {
         using std::begin; using std::end;
         using ValueType = std::remove_cv_t<std::remove_reference_t<decltype(*begin(range))>>;
         return Container<ValueType>(begin(range), end(range));
-    });
+    }};
 }
 
 template<typename ExceptionType, bool exact_size, size_t... Indexes>
 auto elements()
 {
-    return make_view_factory([=] (auto&& range) {
+    return ViewFactory{[=] (auto&& range) {
         using std::begin; using std::end;
         auto it = begin(range), end_it = end(range);
         size_t i = 0;
@@ -551,7 +550,7 @@ auto elements()
         if (exact_size and ++it != end_it)
             throw ExceptionType{++i};
         return res;
-    });
+    }};
 }
 
 template<typename ExceptionType, bool exact_size, size_t... Indexes>
diff --git a/src/string_utils.hh b/src/string_utils.hh
index a11aaa91..1c2d4076 100644
--- a/src/string_utils.hh
+++ b/src/string_utils.hh
@@ -95,9 +95,9 @@ struct WrapView
 
 inline auto wrap_at(ColumnCount max_width)
 {
-    return make_view_factory([=](StringView text) {
+    return ViewFactory{[=](StringView text) {
         return WrapView{text, max_width};
-    });
+    }};
 }
 
 int str_to_int(StringView str); // throws on error
diff --git a/src/utils.hh b/src/utils.hh
index 818cf957..a405659b 100644
--- a/src/utils.hh
+++ b/src/utils.hh
@@ -173,11 +173,11 @@ public:
         }}
     {}
 
-    template<typename Target,
-             typename = std::enable_if_t<
-                 not std::is_same_v<FunctionRef, std::decay_t<Target>> and
-                 std::is_convertible_v<decltype(std::declval<Target>()(std::declval<Args>()...)), Res>
-             >>
+    template<typename Target>
+        requires requires (Target t, Args... a) {
+            requires not std::is_same_v<FunctionRef, std::remove_cvref_t<Target>>;
+            { t(a...) } -> std::convertible_to<Res>;
+        }
     FunctionRef(Target&& target)
       : m_target{&target},
         m_invoker{[](void* target, Args... args) {