From d220c9430a8d1e3e3849349141740b16738cc029 Mon Sep 17 00:00:00 2001
From: Jonathan Marler <johnnymarler@gmail.com>
Date: Thu, 15 Jun 2017 21:55:23 -0600
Subject: [PATCH] Added bitfield support for std.typecons.Flag and other
 boolean variant types.

---
 changelog/std-bitmanip-flags.dd | 41 ++++++++++++++
 std/bitmanip.d                  | 95 +++++++++++++++++++++++++++++++--
 2 files changed, 132 insertions(+), 4 deletions(-)
 create mode 100644 changelog/std-bitmanip-flags.dd

diff --git a/changelog/std-bitmanip-flags.dd b/changelog/std-bitmanip-flags.dd
new file mode 100644
index 00000000000..146f80a17ef
--- /dev/null
+++ b/changelog/std-bitmanip-flags.dd
@@ -0,0 +1,41 @@
+Added support in the std.bitmanip.bitfields function for std.typecons.Flag and other user-defined types that inherit from bool.
+
+This change allows more types to be used in the $(REF bitfields,std,bitmanip) function, for example:
+------
+import std.bitmanip, std.typecons;
+
+enum CustomFlag1 : bool
+{
+    first = false, second = true
+}
+alias CustomFlag2 = Flag!"CustomFlag2";
+template CustomFlag3(string name)
+{
+    enum CustomFlag3 : bool
+    {
+        false_ = false,
+        true_ = true,
+    }
+}
+struct Test
+{
+    mixin(bitfields!(
+        Flag!"a", "a", 1,
+        CustomFlag1, "b", 1,
+        CustomFlag2, "c", 1,
+        CustomFlag3!"something", "d", 1,
+        ubyte, "", 4));
+}
+void main()
+{
+    Test t;
+    t.a = Yes.a;
+    t.b = CustomFlag1.second;
+    t.c = Yes.CustomFlag2;
+    t.d = CustomFlag3!"something".true_;
+    assert(t.a == Yes.a);
+    assert(t.b == CustomFlag1.second);
+    assert(t.c == Yes.CustomFlag2);
+    assert(t.c == CustomFlag3!"something".true_);
+}
+------
diff --git a/std/bitmanip.d b/std/bitmanip.d
index c38a2a8cec4..662599ac82a 100644
--- a/std/bitmanip.d
+++ b/std/bitmanip.d
@@ -61,6 +61,7 @@ import std.traits;
 version(unittest)
 {
     import std.stdio;
+    import std.typecons : Flag, Yes, No;
 }
 
 
@@ -72,6 +73,18 @@ private string myToString(ulong n)
     return cast(string) s ~ (n > uint.max ? "UL" : "U");
 }
 
+private template TypeName(T)
+{
+    static if (__traits(compiles, TemplateOf!T))
+    {
+        enum TypeName = T.stringof ~ "!" ~ TemplateArgsOf!T.stringof[5..$];
+    }
+    else
+    {
+        enum TypeName = T.stringof;
+    }
+}
+
 private template createAccessors(
     string store, T, string name, size_t len, size_t offset)
 {
@@ -105,15 +118,15 @@ private template createAccessors(
             enum extendSign = 0;
         }
 
-        static if (is(T == bool))
+        static if (is(T : bool))
         {
             static assert(len == 1);
             enum result =
             // getter
-                "@property bool " ~ name ~ "() @safe pure nothrow @nogc const { return "
-                ~"("~store~" & "~myToString(maskAllElse)~") != 0;}\n"
+                "@property " ~ TypeName!T ~ " " ~ name ~ "() @safe pure nothrow @nogc const { return "
+                ~"cast(" ~ TypeName!T ~ ")(("~store~" & "~myToString(maskAllElse)~") != 0);}\n"
             // setter
-                ~"@property void " ~ name ~ "(bool v) @safe pure nothrow @nogc { "
+                ~"@property void " ~ name ~ "(" ~ TypeName!T ~ " v) @safe pure nothrow @nogc { "
                 ~"if (v) "~store~" |= "~myToString(maskAllElse)~";"
                 ~"else "~store~" &= ~cast(typeof("~store~"))"~myToString(maskAllElse)~";}\n";
         }
@@ -553,6 +566,80 @@ unittest
     test();
 }
 
+@safe unittest
+{
+    enum CustomFlag1 : bool
+    {
+        first = false, second = true
+    }
+    alias CustomFlag2 = Flag!"CustomFlag2";
+    template CustomFlag3(string name)
+    {
+        enum CustomFlag3 : bool
+        {
+            false_ = false,
+            true_ = true,
+        }
+    }
+    struct Test
+    {
+        mixin(bitfields!(
+            Flag!"a", "a", 1,
+            CustomFlag1, "b", 1,
+            CustomFlag2, "c", 1,
+            CustomFlag3!"something", "d", 1,
+            ubyte, "", 4));
+    }
+    Test t;
+
+    Flag!"a" a;
+    CustomFlag1 b;
+    CustomFlag2 c;
+    CustomFlag3!"something" d;
+
+    void check()
+    {
+        assert(a == t.a);
+        assert(b == t.b);
+        assert(c == t.c);
+        assert(d == t.d);
+    }
+
+    check();
+
+    a = Yes.a;
+    t.a = a;
+    check();
+
+    b = CustomFlag1.second;
+    t.b = b;
+    check();
+
+    c = Yes.CustomFlag2;
+    t.c = c;
+    check();
+
+    d = CustomFlag3!"something".true_;
+    t.d = d;
+    check();
+
+    a = No.a;
+    t.a = a;
+    check();
+
+    b = CustomFlag1.first;
+    t.b = b;
+    check();
+
+    c = No.CustomFlag2;
+    t.c = c;
+    check();
+
+    d = CustomFlag3!"something".false_;
+    t.d = d;
+    check();
+}
+
 @safe unittest
 {
     {