From 7e93bcdeeb985e900bfc4f5a0f87fca5d09a3850 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Wed, 4 Oct 2017 06:06:26 +0200
Subject: [PATCH] meta: Add canFind and isInnerClass

---
 source/tanya/meta/metafunction.d | 35 ++++++++++++++++++--
 source/tanya/meta/trait.d        | 56 ++++++++++++++++++++++++++++++--
 2 files changed, 87 insertions(+), 4 deletions(-)

diff --git a/source/tanya/meta/metafunction.d b/source/tanya/meta/metafunction.d
index ccaa89e..e126ed3 100644
--- a/source/tanya/meta/metafunction.d
+++ b/source/tanya/meta/metafunction.d
@@ -885,8 +885,8 @@ if (Args.length > 0)
  * `-1` is returned if $(D_PARAM T) is not found.
  *
  * Params:
- *  T = The type to search for.
- *  L = Type list.
+ *  T = The item to search for.
+ *  L = Symbol sequence.
  *
  * Returns: The index of the first occurrence of $(D_PARAM T) in $(D_PARAM L).
  */
@@ -910,6 +910,37 @@ pure nothrow @safe @nogc unittest
     static assert(staticIndexOf!(3, () {}, uint, 5, 3) == 3);
 }
 
+/**
+ * Looks for $(D_PARAM T) in $(D_PARAM L) and returns $(D_KEYWORD true) if it
+ * could be found and $(D_KEYWORD false) otherwise.
+ *
+ * Params:
+ *  T = The item to search for.
+ *  L = Symbol sequence.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM T) can be found in $(D_PARAM L),
+ *          $(D_KEYWORD false) otherwise.
+ */
+template canFind(T, L...)
+{
+    enum bool canFind = indexOf!(0, AliasSeq!(T, L)) != -1;
+}
+
+/// ditto
+template canFind(alias T, L...)
+{
+    enum bool canFind = indexOf!(0, AliasSeq!(T, L)) != -1;
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    static assert(!canFind!(int));
+    static assert(canFind!(int, int));
+    static assert(canFind!(int, float, double, int, real));
+    static assert(canFind!(3, () {}, uint, 5, 3));
+}
+
 /**
  * Combines multiple templates with logical AND. So $(D_PSYMBOL templateAnd)
  * evaluates to $(D_INLINECODE Preds[0] && Preds[1] && Preds[2]) and so on.
diff --git a/source/tanya/meta/trait.d b/source/tanya/meta/trait.d
index eb48cb5..bf46fb3 100644
--- a/source/tanya/meta/trait.d
+++ b/source/tanya/meta/trait.d
@@ -660,8 +660,12 @@ enum bool isBasicType(T) = isScalarType!T || is(T : void);
 ///
 pure nothrow @safe @nogc unittest
 {
-    struct S;
-    class C;
+    static struct S
+    {
+    }
+    class C
+    {
+    }
     enum E : int
     {
         i = 0,
@@ -2996,3 +3000,51 @@ pure nothrow @safe @nogc unittest
     static assert(hasUDA!(a, Attr1));
     static assert(!hasUDA!(a, Attr2));
 }
+
+/**
+ * Tests whether $(D_PARAM T) is an inner class, i.e. a class nested inside
+ * another class.
+ *
+ * All inner classes get `outer` propery automatically generated, which points
+ * to its parent class, though it can be explicitly defined to be something
+ * different. If $(D_PARAM T) does this, $(D_PSYMBOL isInnerClass)
+ * evaluates to $(D_KEYWORD false).
+ *
+ * Params:
+ *  T = Class to be tested.
+ *
+ * Returns $(D_KEYWORD true) if $(D_PARAM T) is an inner class,
+ *         $(D_KEYWORD false) otherwise.
+ */
+template isInnerClass(T)
+{
+    static if (is(T == class) && is(Alias!(__traits(parent, T)) == class))
+    {
+        enum bool isInnerClass = !canFind!("outer", __traits(allMembers, T));
+    }
+    else
+    {
+        enum bool isInnerClass = false;
+    }
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    class A
+    {
+    }
+    class O
+    {
+        class I
+        {
+        }
+        class Fake
+        {
+            bool outer;
+        }
+    }
+    static assert(!isInnerClass!(O));
+    static assert(isInnerClass!(O.I));
+    static assert(!isInnerClass!(O.Fake));
+}