From 2b8471fe34b07c4f1ae4aed479d6d1f631881435 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Sun, 24 Mar 2019 21:59:29 +0100
Subject: [PATCH] Add meta.trait.hasFunctionAttributes

---
 meta/tanya/meta/metafunction.d |  4 +--
 meta/tanya/meta/trait.d        | 55 ++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 2 deletions(-)

diff --git a/meta/tanya/meta/metafunction.d b/meta/tanya/meta/metafunction.d
index 8ccafbc..3f8d0e4 100644
--- a/meta/tanya/meta/metafunction.d
+++ b/meta/tanya/meta/metafunction.d
@@ -1779,7 +1779,7 @@ if (T.length == 2)
 }
 
 /**
- * Attaces a numeric index to each element from $(D_PARAM Args).
+ * Attaches a numeric index to each element from $(D_PARAM Args).
  *
  * $(D_PSYMBOL EnumerateFrom) returns a sequence of tuples ($(D_PSYMBOL Pack)s)
  * consisting of the index of each element and the element itself.
@@ -1817,7 +1817,7 @@ template EnumerateFrom(size_t start, Args...)
 }
 
 /**
- * Attaces a numeric index to each element from $(D_PARAM Args).
+ * Attaches a numeric index to each element from $(D_PARAM Args).
  *
  * $(D_PSYMBOL EnumerateFrom) returns a sequence of tuples ($(D_PSYMBOL Pack)s)
  * consisting of the index of each element and the element itself.
diff --git a/meta/tanya/meta/trait.d b/meta/tanya/meta/trait.d
index ae83f24..db9b847 100644
--- a/meta/tanya/meta/trait.d
+++ b/meta/tanya/meta/trait.d
@@ -2257,6 +2257,61 @@ if (isCallable!F)
     static assert((functionAttributes!func1 & FunctionAttribute.return_) == 0);
 }
 
+/**
+ * Determines whether a function has attribute.
+ *
+ * This template should get at least two arguments: the function itself and the
+ * attributes it should be tested for. If more than one attribute is given,
+ * $(D_PSYMBOL hasFunctionAttributes) evaluates to $(D_KEYWORD true) if all of
+ * them are present. The attributes should be $(D_PSYMBOL FunctionAttribute)
+ * members.
+ *
+ * Params:
+ *  Args = The function and attributes.
+ *
+ * Returns:
+ *
+ * See_Also: $(D_PSYMBOL FunctionAttribute).
+ */
+template hasFunctionAttributes(Args...)
+if (Args.length > 1
+ && is(typeof(Args[1]) == FunctionAttribute)
+ && isCallable!(Args[0])
+ && allSameType!(Map!(TypeOf, Args[1 .. $])))
+{
+    enum uint pred(Args_...) = Args_[0] | Args_[1];
+
+    template Reduce(Args_...)
+    {
+        static if (Args_.length == 1)
+        {
+            enum uint Reduce = Args_[0];
+        }
+        else
+        {
+            enum uint Reduce = Reduce!(pred!(Args_[0], Args_[1]), Args_[2 .. $]);
+        }
+    }
+    enum uint field = Reduce!(0, Args[1 .. $]);
+    enum hasFunctionAttributes = (functionAttributes!(Args[0]) & field) == field;
+}
+
+///
+@nogc nothrow pure @safe unittest
+{
+    static struct Range
+    {
+        @property auto front() inout
+        {
+            return 8;
+        }
+    }
+    static assert(hasFunctionAttributes!(Range.init.front, FunctionAttribute.inout_));
+    static assert(!hasFunctionAttributes!(Range.init.front, FunctionAttribute.const_));
+    static assert(!hasFunctionAttributes!(Range.init.front,
+                  FunctionAttribute.inout_, FunctionAttribute.const_));
+}
+
 /**
  * Returns a tuple with default values of the parameters to $(D_PARAM F).
  *