From c67a0d581fcc50df5563c23060b4fcd9dac4c87c Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 17 Apr 2019 10:20:02 -0400
Subject: [PATCH] Add HB_RETURN

---
 src/hb-algs.hh | 13 ++++++-------
 src/hb-meta.hh | 34 ++++++++++++++++++++--------------
 2 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index 232467e49..93677435b 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -50,7 +50,7 @@ struct
 {
   private:
   template <typename T> auto
-  impl (const T& v, hb_priority<1>) const HB_AUTO_RETURN (hb_deref_pointer (v).hash ())
+  impl (const T& v, hb_priority<1>) const HB_RETURN (uint32_t, hb_deref_pointer (v).hash ())
 
   template <typename T,
 	    hb_enable_if (hb_is_integer (T))> auto
@@ -63,7 +63,7 @@ struct
   public:
 
   template <typename T> auto
-  operator () (const T& v) const HB_AUTO_RETURN ((uint32_t) impl (v, hb_prioritize))
+  operator () (const T& v) const HB_RETURN (uint32_t, impl (v, hb_prioritize))
 } HB_FUNCOBJ (hb_hash);
 
 struct
@@ -114,11 +114,10 @@ struct
   public:
 
   template <typename Pred, typename Val> auto
-  operator () (Pred&& p, Val &&v) const HB_AUTO_RETURN
-  (
-    (bool) impl (hb_forward<Pred> (p),
-		 hb_forward<Val> (v),
-		 hb_prioritize)
+  operator () (Pred&& p, Val &&v) const HB_RETURN (bool,
+    impl (hb_forward<Pred> (p),
+	  hb_forward<Val> (v),
+	  hb_prioritize)
   )
 } HB_FUNCOBJ (hb_has);
 
diff --git a/src/hb-meta.hh b/src/hb-meta.hh
index 4a141ce92..0dcf79320 100644
--- a/src/hb-meta.hh
+++ b/src/hb-meta.hh
@@ -34,8 +34,27 @@
  * C++ template meta-programming & fundamentals used with them.
  */
 
+/* Void!  For when we need a expression-type of void. */
+struct hb_void_t { typedef void value; };
+
+/* Void meta-function ala std::void_t
+ * https://en.cppreference.com/w/cpp/types/void_t */
+template<typename... Ts> struct _hb_void_tt { typedef void type; };
+template<typename... Ts> using hb_void_tt = typename _hb_void_tt<Ts...>::type;
+
+template<typename Head, typename... Ts> struct _hb_head_tt { typedef Head type; };
+template<typename... Ts> using hb_head_tt = typename _hb_head_tt<Ts...>::type;
+
+/* Bool!  For when we need to evaluate type-dependent expressions
+ * in a template argument. */
+template <bool b> struct hb_bool_tt { enum { value = b }; };
+typedef hb_bool_tt<true> hb_true_t;
+typedef hb_bool_tt<false> hb_false_t;
+
+
 /* Function overloading SFINAE and priority. */
 
+#define HB_RETURN(Ret, E) -> hb_head_tt<Ret, decltype ((E))> { return (E); }
 #define HB_AUTO_RETURN(E) -> decltype ((E)) { return (E); }
 #define HB_VOID_RETURN(E) -> hb_void_tt<decltype ((E))> { (E); }
 
@@ -45,6 +64,7 @@ template <>             struct hb_priority<0> {};
 
 #define HB_FUNCOBJ(x) static_const x HB_UNUSED
 
+
 struct
 {
   template <typename T>
@@ -98,20 +118,6 @@ struct
 } HB_FUNCOBJ (hb_deref_pointer);
 
 
-/* Void!  For when we need a expression-type of void. */
-struct hb_void_t { typedef void value; };
-
-/* Void meta-function ala std::void_t
- * https://en.cppreference.com/w/cpp/types/void_t */
-template<typename... Ts> struct _hb_void_tt { typedef void type; };
-template<typename... Ts> using hb_void_tt = typename _hb_void_tt<Ts...>::type;
-
-/* Bool!  For when we need to evaluate type-dependent expressions
- * in a template argument. */
-template <bool b> struct hb_bool_tt { enum { value = b }; };
-typedef hb_bool_tt<true> hb_true_t;
-typedef hb_bool_tt<false> hb_false_t;
-
 template<bool B, typename T = void> struct hb_enable_if {};
 template<typename T>                struct hb_enable_if<true, T> { typedef T type; };
 #define hb_enable_if(Cond) typename hb_enable_if<(Cond)>::type* = nullptr