From b8e763fd7140b3e298863e04053ec0f3c73a6a70 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 16 Apr 2019 10:50:22 -0400
Subject: [PATCH] [meta] Add hb_invoke()

---
 src/hb-algs.hh | 34 ++++++++++++++++++++++++++++++++--
 src/hb-iter.hh |  2 +-
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index 1cda64f9b..1460e72fb 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -70,6 +70,29 @@ struct
   operator () (const T& v) const { return bool (v); }
 } HB_FUNCOBJ (hb_bool);
 
+
+struct
+{
+  private:
+
+  // TODO Add overload to for pointer-to-member-function
+
+  template <typename Appl, typename Val> auto
+  impl (Appl&& a, Val &&v, hb_priority<1>) const HB_AUTO_RETURN_EXPR (a (hb_forward<Val> (v)))
+
+  template <typename Appl, typename Val> auto
+  impl (Appl&& a, Val &&v, hb_priority<0>) const HB_AUTO_RETURN_EXPR ((*a) (hb_forward<Val> (v)))
+
+  public:
+
+  template <typename Appl, typename Val> auto
+  operator () (Appl&& a, Val &&v) const HB_AUTO_RETURN_EXPR (
+    impl (hb_forward<Appl> (a),
+	  hb_forward<Val> (v),
+	  hb_prioritize)
+  )
+} HB_FUNCOBJ (hb_invoke);
+
 struct
 {
   private:
@@ -81,7 +104,10 @@ struct
   impl (Pred&& p, Val &&v, hb_priority<1>) const HB_AUTO_RETURN_EXPR (p.has (v))
 
   template <typename Pred, typename Val> auto
-  impl (Pred&& p, Val &&v, hb_priority<0>) const HB_AUTO_RETURN_EXPR (p (v))
+  impl (Pred&& p, Val &&v, hb_priority<0>) const HB_AUTO_RETURN_EXPR (
+    hb_invoke (hb_forward<Pred> (p),
+	       hb_forward<Val> (v))
+  )
 
   public:
 
@@ -104,7 +130,10 @@ struct
   impl (Proj&& f, Val &&v, hb_priority<1>) const HB_AUTO_RETURN_EXPR (f.get (hb_forward<Val> (v)))
 
   template <typename Proj, typename Val> auto
-  impl (Proj&& f, Val &&v, hb_priority<2>) const HB_AUTO_RETURN_EXPR (f (hb_forward<Val> (v)))
+  impl (Proj&& f, Val &&v, hb_priority<2>) const HB_AUTO_RETURN_EXPR (
+    hb_invoke (hb_forward<Proj> (f),
+	       hb_forward<Val> (v))
+  )
 
   public:
 
@@ -116,6 +145,7 @@ struct
   )
 } HB_FUNCOBJ (hb_get);
 
+
 template <typename T1, typename T2>
 struct hb_pair_t
 {
diff --git a/src/hb-iter.hh b/src/hb-iter.hh
index 719987dea..7e7673326 100644
--- a/src/hb-iter.hh
+++ b/src/hb-iter.hh
@@ -471,7 +471,7 @@ struct hb_apply_t
   operator () (Iter it) const
   {
     for (; it; ++it)
-      a (*it);
+      (void) hb_invoke (a, *it);
   }
 
   private: