fix Issue 16291 - EncodingScheme.create fails

- add EncodingScheme.register overload that references the registered class
- just adding the FQN name of a class does not reference that class, so
  it must not end up in the binary and subsequently EncodingScheme.create failed
- This used to work by chance b/c all the EncodingScheme implementations
  were in a module w/ static ctor. Any user of std.encoding did drag in
  that ModuleInfo, which in turn referenced all classes of std.encoding.
  Since moving the static ctor to std.internal.phobosinit to break a
  cycle, the classes were no longer referenced by a ModuleInfo w/ shared
  ctor, so they wouldn't end up in the binary unless explicitly
  referenced elsewhere.
- deprecate the old EncodingScheme.register(string fqn) b/c relying on
  Object.factory is slow, error prone (linkage), and really unnecessary
- import encodinginit in std.encoding so that the
  std_encoding_shared_static_this callback actually gets run

posix.mak

@@ -216,7 +216,7 @@ EXTRA_MODULES_INTERNAL := $(addprefix			\
 	std/internal/digest/, sha_SSSE3 ) $(addprefix \
 	std/internal/math/, biguintcore biguintnoasm biguintx86	\
 	gammafunction errorfunction) $(addprefix std/internal/, \
-	cstring phobosinit processinit unicode_tables scopebuffer\
+	cstring encodinginit processinit unicode_tables scopebuffer\
 	unicode_comp unicode_decomp unicode_grapheme unicode_norm) \
 	$(addprefix std/internal/test/, dummyrange) \
 	$(addprefix std/experimental/ndslice/, internal) \

std/encoding.d

@@ -55,6 +55,7 @@ module std.encoding;
 import std.traits;
 import std.typecons;
 import std.range.primitives;
+import std.internal.encodinginit;
 
 @system unittest
 {
@@ -2360,17 +2361,30 @@ abstract class EncodingScheme
      * This function allows user-defined subclasses of EncodingScheme to
      * be declared in other modules.
      *
+     * Params:
+     *     Klass = The subclass of EncodingScheme to register.
+     *
      * Example:
      * ----------------------------------------------
      * class Amiga1251 : EncodingScheme
      * {
      *     shared static this()
      *     {
-     *         EncodingScheme.register("path.to.Amiga1251");
+     *         EncodingScheme.register!Amiga1251;
      *     }
      * }
      * ----------------------------------------------
      */
+    static void register(Klass:EncodingScheme)()
+    {
+        scope scheme = new Klass();
+        foreach (encodingName;scheme.names())
+        {
+            supported[toLower(encodingName)] = () => new Klass();
+        }
+    }
+
+    deprecated("Please pass the EncodingScheme subclass as template argument instead.")
     static void register(string className)
     {
         auto scheme = cast(EncodingScheme)ClassInfo.find(className).create();
@@ -2378,7 +2392,7 @@ abstract class EncodingScheme
             throw new EncodingException("Unable to create class "~className);
         foreach (encodingName;scheme.names())
         {
-            supported[toLower(encodingName)] = className;
+            supportedFactories[toLower(encodingName)] = className;
         }
     }
 
@@ -2396,7 +2410,12 @@ abstract class EncodingScheme
      */
     static EncodingScheme create(string encodingName)
     {
-        auto p = toLower(encodingName) in supported;
+        encodingName = toLower(encodingName);
+
+        if (auto p = encodingName in supported)
+            return (*p)();
+
+        auto p = encodingName in supportedFactories;
         if (p is null)
             throw new EncodingException("Unrecognized Encoding: "~encodingName);
         string className = *p;
@@ -2650,7 +2669,8 @@ abstract class EncodingScheme
         return t.length - s.length;
     }
 
-    __gshared string[string] supported;
+    __gshared EncodingScheme function()[string] supported;
+    __gshared string[string] supportedFactories;
 }
 
 /**
@@ -3297,6 +3317,20 @@ class EncodingSchemeUtf32Native : EncodingScheme
     assert(ub.length == 8);
 }
 
+
+// shared static this() called from encodinginit to break ctor cycle
+extern(C) void std_encoding_shared_static_this()
+{
+    EncodingScheme.register!EncodingSchemeASCII;
+    EncodingScheme.register!EncodingSchemeLatin1;
+    EncodingScheme.register!EncodingSchemeLatin2;
+    EncodingScheme.register!EncodingSchemeWindows1250;
+    EncodingScheme.register!EncodingSchemeWindows1252;
+    EncodingScheme.register!EncodingSchemeUtf8;
+    EncodingScheme.register!EncodingSchemeUtf16Native;
+    EncodingScheme.register!EncodingSchemeUtf32Native;
+}
+
 //=============================================================================
 
 

std/internal/encodinginit.d

@@ -0,0 +1,19 @@
+// Written in the D programming language.
+
+/++
+    The purpose of this module is to perform static construction away from the
+    normal modules to eliminate cyclic construction errors.
+
+    Copyright: Copyright 2011 - 2016
+    License:   $(HTTP www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
+    Authors:   Martin Nowak, Steven Schveighoffer
+    Source:    $(PHOBOSSRC std/internal/_encodinginit.d)
+  +/
+module std.internal.encodinginit;
+
+extern(C) void std_encoding_shared_static_this();
+
+shared static this()
+{
+    std_encoding_shared_static_this();
+}

std/internal/phobosinit.d

@@ -1,25 +0,0 @@
-// Written in the D programming language.
-
-/++
-    The purpose of this module is to perform static construction away from the
-    normal modules to eliminate cyclic construction errors.
-
-    Copyright: Copyright 2011 - 2016
-    License:   $(HTTP www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
-    Authors:   Jonathan M Davis, Kato Shoichi, Steven Schveighoffer
-    Source:    $(PHOBOSSRC std/internal/_phobosinit.d)
-  +/
-module std.internal.phobosinit;
-
-shared static this()
-{
-    import std.encoding : EncodingScheme;
-    EncodingScheme.register("std.encoding.EncodingSchemeASCII");
-    EncodingScheme.register("std.encoding.EncodingSchemeLatin1");
-    EncodingScheme.register("std.encoding.EncodingSchemeLatin2");
-    EncodingScheme.register("std.encoding.EncodingSchemeWindows1250");
-    EncodingScheme.register("std.encoding.EncodingSchemeWindows1252");
-    EncodingScheme.register("std.encoding.EncodingSchemeUtf8");
-    EncodingScheme.register("std.encoding.EncodingSchemeUtf16Native");
-    EncodingScheme.register("std.encoding.EncodingSchemeUtf32Native");
-}

win32.mak

@@ -267,7 +267,7 @@ SRC_STD_C_FREEBSD= \
 
 SRC_STD_INTERNAL= \
 	std\internal\cstring.d \
-	std\internal\phobosinit.d \
+	std\internal\encodinginit.d \
 	std\internal\processinit.d \
 	std\internal\unicode_tables.d \
 	std\internal\unicode_comp.d \

win64.mak

@@ -286,7 +286,7 @@ SRC_STD_C_FREEBSD= \
 
 SRC_STD_INTERNAL= \
 	std\internal\cstring.d \
-	std\internal\phobosinit.d \
+	std\internal\encodinginit.d \
 	std\internal\processinit.d \
 	std\internal\unicode_tables.d \
 	std\internal\unicode_comp.d \