Remove DUK_USE_NONSTD_ARRAY_CONCAT_TRAILER option

config/config-options/DUK_USE_NONSTD_ARRAY_CONCAT_TRAILER.yaml

@@ -1,14 +1,11 @@
 define: DUK_USE_NONSTD_ARRAY_CONCAT_TRAILER
 introduced: 1.0.0
+removed: 2.3.0
 default: true
 tags:
   - ecmascript
   - compliance
 description: >
-  For better compatibility with existing code, enable non-standard
-  Array.prototype.concat() behavior for trailing non-existent elements of
-  the concat result, see
-  https://github.com/svaarala/duktape/blob/master/tests/ecmascript/test-bi-array-proto-concat-nonstd-trailing.js.
-
-  If this option is disabled, concat() will behave in a strictly conforming
-  fashion, ignoring non-existent trailing elements in the result length.
+  In ES5.1 trailing gaps of an argument array don't count towards the result
+  length.  This is in essence a specification "bug" which was fixed in ES2015.
+  This option was removed in 2.3.0, and the remaining behavior matches ES2015.

config/examples/compliance.yaml

@@ -1,6 +1,5 @@
 # Enable compliant behavior, defaults favor "real world" compatibility.
 
-DUK_USE_NONSTD_ARRAY_CONCAT_TRAILER: false
 DUK_USE_NONSTD_ARRAY_MAP_TRAILER: false
 DUK_USE_NONSTD_ARRAY_SPLICE_DELCOUNT: false
 DUK_USE_NONSTD_FUNC_CALLER_PROPERTY: false

util/makeduk_base.yaml

@@ -55,7 +55,6 @@ DUK_USE_DEBUGGER_INSPECT: true
 #DUK_USE_NONSTD_FUNC_CALLER_PROPERTY: true
 #DUK_USE_NONSTD_FUNC_SOURCE_PROPERTY: true
 #DUK_USE_NONSTD_ARRAY_SPLICE_DELCOUNT: false
-#DUK_USE_NONSTD_ARRAY_CONCAT_TRAILER: false
 #DUK_USE_NONSTD_ARRAY_MAP_TRAILER: false
 #DUK_USE_NONSTD_JSON_ESC_U2028_U2029: false
 #DUK_USE_NONSTD_STRING_FROMCHARCODE_32BIT: false