Correct encoding of several layers of embedded structs

I'm not entirely sure if I understand what's going on here, but this
seems to fix it.

Fixes #430

Author: arp242

Diff for: encode.go

@@ -440,8 +440,6 @@ func (enc *Encoder) eMap(key Key, rv reflect.Value, inline bool) {
 	}
 }
 
-const is32Bit = (32 << (^uint(0) >> 63)) == 32
-
 func pointerTo(t reflect.Type) reflect.Type {
 	if t.Kind() == reflect.Ptr {
 		return pointerTo(t.Elem())
@@ -476,15 +474,14 @@ func (enc *Encoder) eStruct(key Key, rv reflect.Value, inline bool) {
 
 			frv := eindirect(rv.Field(i))
 
-			if is32Bit {
-				// Copy so it works correct on 32bit archs; not clear why this
-				// is needed. See #314, and https://www.reddit.com/r/golang/comments/pnx8v4
-				// This also works fine on 64bit, but 32bit archs are somewhat
-				// rare and this is a wee bit faster.
-				copyStart := make([]int, len(start))
-				copy(copyStart, start)
-				start = copyStart
-			}
+			// Need to make a copy because ... ehm, I don't know why... I guess
+			// allocating a new array can cause it to fail(?)
+			//
+			// Done for: https://github.com/BurntSushi/toml/issues/430
+			// Previously only on 32bit for: https://github.com/BurntSushi/toml/issues/314
+			copyStart := make([]int, len(start))
+			copy(copyStart, start)
+			start = copyStart
 
 			// Treat anonymous struct fields with tag names as though they are
 			// not anonymous, like encoding/json does.

Diff for: encode_test.go

@@ -836,6 +836,17 @@ func TestEncodeJSONNumber(t *testing.T) {
 	}
 }
 
+type (
+	StructA struct{ StructB }
+	StructB struct{ StructC }
+	StructC struct{ StructD }
+	StructD struct {
+		FieldD1 string
+		FieldD2 string
+		FieldD3 string
+	}
+)
+
 func TestEncode(t *testing.T) {
 	type (
 		Embedded struct {
@@ -1114,6 +1125,20 @@ ArrayOfMixedSlices = [[1, 2], ["a", "b"]]
 			}{struct{ Embedded }{Embedded{1}}},
 			wantOutput: "[_struct]\n  _int = 1\n",
 		},
+		"deeply nested embedded struct": { // #430
+			input: StructA{
+				StructB: StructB{
+					StructC: StructC{
+						StructD: StructD{
+							FieldD1: "V1",
+							FieldD2: "V2",
+							FieldD3: "V3",
+						},
+					},
+				},
+			},
+			wantOutput: "FieldD1 = \"V1\"\nFieldD2 = \"V2\"\nFieldD3 = \"V3\"\n",
+		},
 		"nested embedded *struct": {
 			input: struct {
 				Struct struct{ *Embedded } `toml:"_struct"`