[builtins] Implement Array.from in CodeStubAssembler

This removes the Javascript version of Array.from in js/array.js and
adds a CodeStubAssembler version in src/builtins/builtins-array-gen.cc.

Also modify IteratorBuiltinsAssembler to allow querying the existence
of the iterator method without calling it so we can fall back to the
array-like behavior.

BUG=v8:1956

Change-Id: Ibfb3cef002d72d70bd30b4de676fd22becde006c
Reviewed-on: https://chromium-review.googlesource.com/887066Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51208}

src/bootstrapper.cc

@@ -1705,6 +1705,8 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
         array_function, "isArray", Builtins::kArrayIsArray, 1, true);
     native_context()->set_is_arraylike(*is_arraylike);
 
+    SimpleInstallFunction(array_function, "from", Builtins::kArrayFrom, 1,
+                          false);
     SimpleInstallFunction(array_function, "of", Builtins::kArrayOf, 0, false);
 
     JSObject::AddProperty(proto, factory->constructor_string(), array_function,

src/builtins/builtins-definitions.h

@@ -244,6 +244,8 @@ namespace internal {
   CPP(ArrayConcat)                                                             \
   /* ES6 #sec-array.isarray */                                                 \
   TFJ(ArrayIsArray, 1, kArg)                                                   \
+  /* ES6 #sec-array.from */                                                    \
+  TFJ(ArrayFrom, SharedFunctionInfo::kDontAdaptArgumentsSentinel)              \
   /* ES6 #sec-array.of */                                                      \
   TFJ(ArrayOf, SharedFunctionInfo::kDontAdaptArgumentsSentinel)                \
   /* ES7 #sec-array.prototype.includes */                                      \

src/builtins/builtins-iterator-gen.cc

@@ -11,11 +11,16 @@ namespace internal {
 
 using compiler::Node;
 
+Node* IteratorBuiltinsAssembler::GetIteratorMethod(Node* context,
+                                                   Node* object) {
+  return GetProperty(context, object, factory()->iterator_symbol());
+}
+
 IteratorRecord IteratorBuiltinsAssembler::GetIterator(Node* context,
                                                       Node* object,
                                                       Label* if_exception,
                                                       Variable* exception) {
-  Node* method = GetProperty(context, object, factory()->iterator_symbol());
+  Node* method = GetIteratorMethod(context, object);
   return GetIterator(context, object, method, if_exception, exception);
 }
 

src/builtins/builtins-iterator-gen.h

@@ -17,6 +17,9 @@ class IteratorBuiltinsAssembler : public CodeStubAssembler {
   explicit IteratorBuiltinsAssembler(compiler::CodeAssemblerState* state)
       : CodeStubAssembler(state) {}
 
+  // Returns object[Symbol.iterator].
+  Node* GetIteratorMethod(Node* context, Node* object);
+
   // https://tc39.github.io/ecma262/#sec-getiterator --- never used for
   // @@asyncIterator.
   IteratorRecord GetIterator(Node* context, Node* object,

src/compiler/code-assembler.h

@@ -1157,6 +1157,9 @@ class TypedCodeAssemblerVariable : public CodeAssemblerVariable {
   operator Node*() const { return value(); }
 
   void operator=(TNode<T> value) { Bind(value); }
+  void operator=(const TypedCodeAssemblerVariable<T>& variable) {
+    Bind(variable.value());
+  }
 
  private:
   using CodeAssemblerVariable::Bind;

src/js/array.js

@@ -1153,63 +1153,6 @@ DEFINE_METHOD_LEN(
   1  /* Set function length */
 );
 
-
-// ES6, draft 10-14-14, section 22.1.2.1
-DEFINE_METHOD_LEN(
-  GlobalArray,
-  'from'(arrayLike, mapfn, receiver) {
-    var items = TO_OBJECT(arrayLike);
-    var mapping = !IS_UNDEFINED(mapfn);
-
-    if (mapping) {
-      if (!IS_CALLABLE(mapfn)) {
-        throw %make_type_error(kCalledNonCallable, mapfn);
-      }
-    }
-
-    var iterable = GetMethod(items, iteratorSymbol);
-    var k;
-    var result;
-    var mappedValue;
-    var nextValue;
-
-    if (!IS_UNDEFINED(iterable)) {
-      result = %IsConstructor(this) ? new this() : [];
-      k = 0;
-
-      for (nextValue of
-           { [iteratorSymbol]() { return GetIterator(items, iterable) } }) {
-        if (mapping) {
-          mappedValue = %_Call(mapfn, receiver, nextValue, k);
-        } else {
-          mappedValue = nextValue;
-        }
-        %CreateDataProperty(result, k, mappedValue);
-        k++;
-      }
-      result.length = k;
-      return result;
-    } else {
-      var len = TO_LENGTH(items.length);
-      result = %IsConstructor(this) ? new this(len) : new GlobalArray(len);
-
-      for (k = 0; k < len; ++k) {
-        nextValue = items[k];
-        if (mapping) {
-          mappedValue = %_Call(mapfn, receiver, nextValue, k);
-        } else {
-          mappedValue = nextValue;
-        }
-        %CreateDataProperty(result, k, mappedValue);
-      }
-
-      result.length = k;
-      return result;
-    }
-  },
-  1  /* Set function length. */
-);
-
 // Set up unscopable properties on the Array.prototype object.
 var unscopables = {
   __proto__: null,

test/mjsunit/es6/array-from.js

@@ -161,6 +161,14 @@ assertThrows(function () { Array.from.call(exotic, [1]); }, TypeError);
 // The setter wasn't called
 assertEquals(0, setterCalled);
 
+// Non-callable iterators should cause a TypeError before calling the target
+// constructor.
+items = {};
+items[Symbol.iterator] = 7;
+function TestError() {}
+function ArrayLike() { throw new TestError() }
+assertThrows(function() { Array.from.call(ArrayLike, items); }, TypeError);
+
 // Check that array properties defined are writable, enumerable, configurable
 function ordinary() { }
 var x = Array.from.call(ordinary, [2]);