Bug 1931350: Add initial implementation for the Iterator Sequencing p…

…roposal. r=mgaudet

Test PR: tc39/test262#4326

Differential Revision: https://phabricator.services.mozilla.com/D229014

UltraBlame original commit: 8d892ee60eeedad56dde64e3aa91c63abd10e8e0

js/src/builtin/Iterator.js

@@ -2326,6 +2326,265 @@ value
 ifdef
 NIGHTLY_BUILD
 function
+IteratorConcat
+(
+)
+{
+var
+index
+=
+ArgumentsLength
+(
+)
+*
+2
+;
+var
+iterables
+=
+std_Array
+(
+index
+)
+;
+for
+(
+var
+i
+=
+0
+;
+i
+<
+ArgumentsLength
+(
+)
+;
+i
++
++
+)
+{
+var
+item
+=
+GetArgument
+(
+i
+)
+;
+if
+(
+!
+IsObject
+(
+item
+)
+)
+{
+ThrowTypeError
+(
+JSMSG_OBJECT_REQUIRED
+typeof
+item
+)
+;
+}
+var
+method
+=
+item
+[
+GetBuiltinSymbol
+(
+"
+iterator
+"
+)
+]
+;
+if
+(
+!
+IsCallable
+(
+method
+)
+)
+{
+ThrowTypeError
+(
+JSMSG_NOT_ITERABLE
+ToSource
+(
+item
+)
+)
+;
+}
+DefineDataProperty
+(
+iterables
+-
+-
+index
+item
+)
+;
+DefineDataProperty
+(
+iterables
+-
+-
+index
+method
+)
+;
+}
+assert
+(
+index
+=
+=
+=
+0
+"
+all
+items
+stored
+"
+)
+;
+var
+result
+=
+NewIteratorHelper
+(
+)
+;
+var
+generator
+=
+IteratorConcatGenerator
+(
+iterables
+)
+;
+UnsafeSetReservedSlot
+(
+result
+ITERATOR_HELPER_GENERATOR_SLOT
+generator
+)
+;
+return
+result
+;
+}
+function
+*
+IteratorConcatGenerator
+(
+iterables
+)
+{
+assert
+(
+IsArray
+(
+iterables
+)
+"
+iterables
+is
+an
+array
+"
+)
+;
+assert
+(
+iterables
+.
+length
+%
+2
+=
+=
+=
+0
+"
+iterables
+contains
+pairs
+(
+item
+method
+)
+"
+)
+;
+for
+(
+var
+i
+=
+iterables
+.
+length
+;
+i
+>
+0
+;
+)
+{
+var
+item
+=
+iterables
+[
+-
+-
+i
+]
+;
+var
+method
+=
+iterables
+[
+-
+-
+i
+]
+;
+iterables
+.
+length
+-
+=
+2
+;
+for
+(
+var
+innerValue
+of
+allowContentIterWith
+(
+item
+method
+)
+)
+{
+yield
+innerValue
+;
+}
+}
+}
+function
 IteratorZip
 (
 predicate

js/src/vm/CommonPropertyNames.h

@@ -646,6 +646,14 @@ compare
 \
 MACRO_
 (
+concat
+"
+concat
+"
+)
+\
+MACRO_
+(
 configurable
 "
 configurable

js/src/vm/Iteration.cpp

@@ -9316,6 +9316,17 @@ NIGHTLY_BUILD
 JS_SELF_HOSTED_FN
 (
 "
+concat
+"
+"
+IteratorConcat
+"
+0
+0
+)
+JS_SELF_HOSTED_FN
+(
+"
 range
 "
 "

js/src/vm/JSObject.cpp

@@ -12963,6 +12963,46 @@ if
 key
 =
 =
+JSProto_Function
+&
+&
+!
+JS
+:
+:
+Prefs
+:
+:
+experimental_iterator_sequencing
+(
+)
+&
+&
+id
+=
+=
+NameToId
+(
+cx
+-
+>
+names
+(
+)
+.
+concat
+)
+)
+{
+return
+true
+;
+}
+if
+(
+key
+=
+=
 JSProto_Atomics
 &
 &