Add the TypeOf template.

source/taggedalgebraic.d

@@ -658,6 +658,34 @@ unittest {
 }
 
 
+/** Maps a kind enumeration value to the corresponding field type.
+
+	`kind` must be a value of the `TaggedAlgebraic!T.Kind` enumeration.
+*/
+template TypeOf(alias kind)
+	if (isInstanceOf!(TypeEnum, typeof(kind)))
+{
+	import std.traits : FieldTypeTuple, TemplateArgsOf;
+	alias U = TemplateArgsOf!(typeof(kind));
+	alias TypeOf = FieldTypeTuple!U[kind];
+}
+
+///
+unittest {
+	static struct S {
+		int a;
+		string b;
+		string c;
+	}
+	alias TA = TaggedAlgebraic!S;
+
+	static assert(is(TypeOf!(TA.Kind.a) == int));
+	static assert(is(TypeOf!(TA.Kind.b) == string));
+	static assert(is(TypeOf!(TA.Kind.c) == string));
+}
+
+
+
 /** Gets the value stored in an algebraic type based on its data type.
 */
 ref inout(T) get(T, U)(ref inout(TaggedAlgebraic!U) ta)