Add m-esr52 at 52.6.0

10 files changed, 487 insertions, 0 deletions

diff --git a/js/src/tests/ecma_6/Comprehensions/arguments.js b/js/src/tests/ecma_6/Comprehensions/arguments.js
new file mode 100644
index 000000000..082374778
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/arguments.js
@@ -0,0 +1,14 @@
+
+
+function values(g) {
+  return [for (x of g) x];
+}
+
+function argumentsTest() {
+  return values((for (i of [0,1,2]) arguments[i]));
+}
+
+assertDeepEq(argumentsTest('a', 'b', 'c'), ['a', 'b', 'c']);
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
diff --git a/js/src/tests/ecma_6/Comprehensions/array-yield.js b/js/src/tests/ecma_6/Comprehensions/array-yield.js
new file mode 100644
index 000000000..69e699522
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/array-yield.js
@@ -0,0 +1,23 @@
+// Interactions between yield and array comprehensions.
+
+
+function assertIteratorResult(result, value, done) {
+    assertDeepEq(result.value, value);
+    assertEq(result.done, done);
+}
+
+function* t1() { return [for (x of yield 0) x*2] }
+
+var o = t1();
+assertIteratorResult(o.next(), 0, false);
+assertIteratorResult(o.next([0, 1, 2]), [0, 2, 4], true);
+
+function* t2() { return [for (x of [1,2,3]) yield x] }
+
+o = t2();
+assertIteratorResult(o.next(), 1, false);
+assertIteratorResult(o.next(5), 2, false);
+assertIteratorResult(o.next(6), 3, false);
+assertIteratorResult(o.next(7), [5, 6, 7], true);
+
+reportCompare(null, null, "test");
diff --git a/js/src/tests/ecma_6/Comprehensions/error-messages.js b/js/src/tests/ecma_6/Comprehensions/error-messages.js
new file mode 100644
index 000000000..aeacfde27
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/error-messages.js
@@ -0,0 +1,172 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+// This file tests contextual restrictions for yield and arguments, and is
+// derived from js1_8/genexps/regress-634472.js.
+
+function error(str) {
+  var base;
+  try {
+    // the following line must not be broken up into multiple lines
+    base = (function(){try{eval('throw new Error()')}catch(e){return e.lineNumber}})(); eval(str);
+    return null;
+  } catch (e) {
+    e.lineNumber = e.lineNumber - base + 1;
+    return e;
+  }
+}
+
+const YIELD_PAREN          = error("(function*(){(for (y of (yield 1, 2)) y)})").message;
+const GENEXP_YIELD         = error("(function*(){(for (x of yield 1) x)})").message;
+const TOP_YIELD            = error("yield").message;
+const GENERIC              = error("(for)").message;
+const BAD_GENERATOR_SYNTAX = error("(for (x of []) x, 1)").message;
+const MISSING_SEMI         = error("yield 1").message;
+const PAREN_PAREN          = error("(foo").message;
+const FOR_OF_PAREN         = error("(for (x of y, z) w)").message;
+
+const cases = [
+// Expressions involving yield without a value, not currently implemented.  Many
+// of these errors would need to be updated.  (Note: line numbers below might be
+// mere placeholders, not actually the expected correct behavior -- check before
+// blindly uncommenting.)
+//{ expr: "yield",        top: [TOP_YIELD, 777], fun: null,              gen: [GENEXP_YIELD, 2], desc: "simple yield" },
+//{ expr: "1, yield",     top: [TOP_YIELD, 777], fun: null,              gen: [GENEXP_YIELD, 2], desc: "simple yield at end of list" },
+//{ expr: "yield, 1",     top: [TOP_YIELD, 777], fun: [YIELD_PAREN, 2], gen: [YIELD_PAREN, 2],  desc: "simple yield in list" },
+//{ expr: "(yield)",      top: [TOP_YIELD, 777], fun: null,              gen: [GENEXP_YIELD, 2], desc: "simple yield, parenthesized" },
+//{ expr: "(1, yield)",   top: [TOP_YIELD, 777], fun: null,              gen: [GENEXP_YIELD, 2], desc: "simple yield at end of list, parenthesized" },
+//{ expr: "(yield, 1)",   top: [TOP_YIELD, 777], fun: [YIELD_PAREN, 2], gen: [YIELD_PAREN, 2],  desc: "simple yield in list, parenthesized" },
+//{ expr: "((((yield))))",   top: [TOP_YIELD, 777], fun: null, gen: [GENEXP_YIELD, 2], desc: "deeply nested yield" },
+//{ expr: "(for (x of []) yield)",           top: [TOP_YIELD, 777], fun: [GENERIC, 777],      gen: [GENERIC, 777],      desc: "simple yield in genexp" },
+//{ expr: "(for (x of []) yield, 1)",        top: [TOP_YIELD, 777], fun: [YIELD_PAREN, 2],  gen: [YIELD_PAREN, 2],  desc: "simple yield in list in genexp" },
+//{ expr: "(for (x of []) 1, yield)",        top: [TOP_YIELD, 777], fun: [GENERIC, 777],      gen: [GENERIC, 777],      desc: "simple yield at end of list in genexp" },
+//{ expr: "(for (x of []) (yield))",         top: [TOP_YIELD, 777], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], desc: "simple yield, parenthesized in genexp" },
+//{ expr: "(for (x of []) 1, (yield))",      top: [TOP_YIELD, 777], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], desc: "simple yield, parenthesized in list in genexp" },
+//{ expr: "(for (x of []) (1, yield))",      top: [TOP_YIELD, 777], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], desc: "simple yield at end of list, parenthesized in genexp" },
+//{ expr: "(for (x of []) 1, (2, yield))",   top: [TOP_YIELD, 777], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], desc: "simple yield at end of list, parenthesized in list in genexp" },
+//{ expr: "(for (x of []) (yield, 1))",      top: [TOP_YIELD, 777], fun: [YIELD_PAREN, 2],  gen: [YIELD_PAREN, 2],  desc: "simple yield in list, parenthesized in genexp" },
+//{ expr: "(for (x of []) 1, (yield, 2))",   top: [TOP_YIELD, 777], fun: [YIELD_PAREN, 2],  gen: [YIELD_PAREN, 2],  desc: "simple yield in list, parenthesized in list in genexp" },
+//{ expr: "(for (x of []) (function*() { yield }))",           top: null, fun: null, gen: null, desc: "legal yield in nested function" },
+
+  // yield expressions
+  { expr: "yield 1",      top: [MISSING_SEMI, 2], fun: [MISSING_SEMI, 2], gen: null, genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg" },
+  { expr: "1, yield 2",   top: [MISSING_SEMI, 2], fun: [MISSING_SEMI, 2], gen: null, genexp: [FOR_OF_PAREN, 1], desc: "yield w/ arg at end of list" },
+  { expr: "yield 1, 2",   top: [MISSING_SEMI, 2], fun: [MISSING_SEMI, 2], gen: null, genexp: [FOR_OF_PAREN, 3], desc: "yield w/ arg in list" },
+  { expr: "(yield 1)",    top: [PAREN_PAREN, 2], fun:  [PAREN_PAREN, 2], gen: null, genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg, parenthesized" },
+  { expr: "(1, yield 2)", top: [PAREN_PAREN, 2], fun:  [PAREN_PAREN, 2], gen: null, genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg at end of list, parenthesized" },
+  { expr: "(yield 1, 2)", top: [PAREN_PAREN, 2], fun:  [PAREN_PAREN, 2], gen: null, genexp: [YIELD_PAREN, 2], desc: "yield w/ arg in list, parenthesized" },
+
+  // deeply nested yield expressions
+  { expr: "((((yield 1))))", top: [PAREN_PAREN, 2], fun: [PAREN_PAREN, 2], gen: null, genexp: [GENEXP_YIELD, 2], desc: "deeply nested yield w/ arg" },
+
+  // arguments
+  { expr: "arguments",    top: null, fun: null, gen: null, genexp: null, desc: "arguments in list" },
+  { expr: "1, arguments", top: null, fun: null, gen: null, genexp: [FOR_OF_PAREN, 1], desc: "arguments in list" },
+
+  // yield in generator expressions
+  { expr: "(for (x of []) yield 1)",         top: [GENEXP_YIELD, 2], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg in genexp" },
+  { expr: "(for (x of []) yield 1, 2)",      top: [GENEXP_YIELD, 2], fun: [GENEXP_YIELD, 2],  gen: [GENEXP_YIELD, 2], genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg in list in genexp" },
+  { expr: "(for (x of []) 1, yield 2)",      top: [PAREN_PAREN, 1], fun: [PAREN_PAREN, 1],  gen: [PAREN_PAREN, 1], genexp: [PAREN_PAREN, 1], desc: "yield w/ arg at end of list in genexp" },
+  { expr: "(for (x of []) (yield 1))",       top: [GENEXP_YIELD, 2], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg, parenthesized in genexp" },
+  { expr: "(for (x of []) 1, (yield 2))",    top: [PAREN_PAREN, 1], fun: [PAREN_PAREN, 1], gen: [PAREN_PAREN, 1], genexp: [PAREN_PAREN, 1], desc: "yield w/ arg, parenthesized in list in genexp" },
+  { expr: "(for (x of []) (1, yield 2))",    top: [GENEXP_YIELD, 2], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], genexp: [GENEXP_YIELD, 2], desc: "yield w/ arg at end of list, parenthesized in genexp" },
+  { expr: "(for (x of []) 1, (2, yield 3))", top: [PAREN_PAREN, 1], fun: [PAREN_PAREN, 1], gen: [PAREN_PAREN, 1], genexp: [PAREN_PAREN, 1], desc: "yield w/ arg at end of list, parenthesized in list in genexp" },
+  { expr: "(for (x of []) (yield 1, 2))",    top: [YIELD_PAREN, 2], fun: [YIELD_PAREN, 2], gen: [YIELD_PAREN, 2], genexp: [YIELD_PAREN, 2], desc: "yield w/ arg in list, parenthesized in genexp" },
+  { expr: "(for (x of []) 1, (yield 2, 3))", top: [PAREN_PAREN, 1], fun: [PAREN_PAREN, 1], gen: [PAREN_PAREN, 1], genexp: [PAREN_PAREN, 1], desc: "yield w/ arg in list, parenthesized in list in genexp" },
+
+  // deeply nested yield in generator expressions
+  { expr: "(for (x of []) (((1, yield 2))))",               top: [GENEXP_YIELD, 2], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], genexp: [GENEXP_YIELD, 2], desc: "deeply nested yield in genexp" },
+  { expr: "(for (y of []) (for (x of []) ((1, yield 2))))", top: [GENEXP_YIELD, 2], fun: [GENEXP_YIELD, 2], gen: [GENEXP_YIELD, 2], genexp: [GENEXP_YIELD, 2], desc: "deeply nested yield in multiple genexps" },
+
+  // arguments in generator expressions
+  { expr: "(for (x of []) arguments)",         top: null, fun: null, gen: null, genexp: null, desc: "simple arguments in genexp" },
+  { expr: "(for (x of []) 1, arguments)",      top: [BAD_GENERATOR_SYNTAX, 1], fun: [BAD_GENERATOR_SYNTAX, 1], gen: [BAD_GENERATOR_SYNTAX, 1], genexp: [BAD_GENERATOR_SYNTAX, 1], desc: "arguments in list in genexp" },
+  { expr: "(for (x of []) (arguments))",       top: null, fun: null, gen: null, genexp: null, desc: "arguments, parenthesized in genexp" },
+  { expr: "(for (x of []) 1, (arguments))",    top: [BAD_GENERATOR_SYNTAX, 1], fun: [BAD_GENERATOR_SYNTAX, 1], gen: [BAD_GENERATOR_SYNTAX, 1], genexp: [BAD_GENERATOR_SYNTAX, 1], desc: "arguments, parenthesized in list in genexp" },
+  { expr: "(for (x of []) (1, arguments))",    top: null, fun: null, gen: null, genexp: null, desc: "arguments in list, parenthesized in genexp" },
+  { expr: "(for (x of []) 1, (2, arguments))", top: [BAD_GENERATOR_SYNTAX, 1], fun: [BAD_GENERATOR_SYNTAX, 1], gen: [BAD_GENERATOR_SYNTAX, 1], genexp: [BAD_GENERATOR_SYNTAX, 1], desc: "arguments in list, parenthesized in list in genexp" },
+
+  // deeply nested arguments in generator expressions
+  { expr: "(for (x of []) (((1, arguments))))",               top: null, fun: null, gen: null, genexp: null, desc: "deeply nested arguments in genexp" },
+  { expr: "(for (y of []) (for (x of []) ((1, arguments))))", top: null, fun: null, gen: null, genexp: null, desc: "deeply nested arguments in multiple genexps" },
+
+  // legal yield/arguments in nested function
+  { expr: "(for (x of []) (function*() { yield 1 }))",         top: null, fun: null, gen: null, genexp: null, desc: "legal yield in nested function" },
+  { expr: "(for (x of []) (function() { arguments }))",       top: null, fun: null, gen: null, genexp: null, desc: "legal arguments in nested function" },
+  { expr: "(for (x of []) (function() arguments))",           top: null, fun: null, gen: null, genexp: null, desc: "legal arguments in nested expression-closure" }
+];
+
+//-----------------------------------------------------------------------------
+test();
+//-----------------------------------------------------------------------------
+
+function splitKeyword(str) {
+  return str.
+//         replace(/[)] yield/, ')\nyield\n').
+         replace(/yield ([0-9])/, '\nyield $1\n').
+         replace(/yield([^ ]|$)/, '\nyield\n$1').
+         replace(/arguments/, '\narguments\n');
+}
+
+function expectError1(err, ctx, msg, lineNumber) {
+  reportCompare('object', typeof err,     'exn for: ' + msg);
+  reportCompare(ctx,      err.message,    'exn message for: ' + msg);
+  reportCompare(lineNumber,    err.lineNumber, 'exn token for: ' + msg);
+}
+
+function expectError(expr, wrapCtx, [expect, lineNumber], msg) {
+  expectError1(error(wrapCtx(expr)), expect, msg, lineNumber);
+}
+
+function expectSuccess(err, msg) {
+  reportCompare(null, err, 'parse: ' + msg);
+}
+
+function atTop(str) { return str }
+function inFun(str) { return '(function(){' + str + '})' }
+function inGen(str) { return '(function*(){' + str + '})' }
+function inGenExp(str) { return '(for (y of ' + str + ') y)' }
+
+function test()
+{
+  enterFunc ('test');
+  printBugNumber(BUGNUMBER);
+  printStatus (summary);
+
+  for (var i = 0, len = cases.length; i < len; i++) {
+    var expr, top, fun, gen, genexp, desc;
+    expr = cases[i].expr;
+    top = cases[i].top;
+    fun = cases[i].fun;
+    gen = cases[i].gen;
+    genexp = cases[i].genexp;
+    desc = cases[i].desc;
+
+    expr = splitKeyword(expr);
+
+    if (top)
+      expectError(expr, atTop, top, 'top-level context, ' + desc);
+    else
+      expectSuccess(error(expr), 'top-level context, ' + desc);
+
+    if (fun)
+      expectError(expr, inFun, fun, 'function context, ' + desc);
+    else
+      expectSuccess(error(inFun(expr)), 'function context, ' + desc);
+
+    if (gen)
+      expectError(expr, inGen, gen, 'generator context, ' + desc);
+    else
+      expectSuccess(error(inGen(expr)), 'generator context, ' + desc);
+
+    if (genexp)
+      expectError(expr, inGenExp, genexp, 'genexp context, ' + desc);
+    else
+      expectSuccess(error(inGenExp(expr)), 'genexp context, ' + desc);
+  }
+
+  exitFunc ('test');
+}
diff --git a/js/src/tests/ecma_6/Comprehensions/generator-semantics.js b/js/src/tests/ecma_6/Comprehensions/generator-semantics.js
new file mode 100644
index 000000000..52426115f
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/generator-semantics.js
@@ -0,0 +1,52 @@
+// Interaction of eval with generator expressions.
+function a1() {
+  var a = 10;
+  var g = (for (y of [0]) eval('var a=42;'));
+  g.next();
+  return a;
+}
+assertEq(a1(), 10);
+
+function a2() {
+  var a = 10;
+  (for (y of [0]) eval('a=42')).next();
+  return a;
+}
+assertEq(a2(), 42)
+
+// Arguments and this.
+function b1() {
+  return [for (arg of (for (i of [0, 1, 2]) arguments[i])) arg];
+}
+assertDeepEq(b1('a', 'b', 'c'), ['a', 'b', 'c']);
+
+function b2() {
+  return [for (x of (for (i of [0]) this)) x];
+}
+var b2o = { b2: b2 }
+assertDeepEq(b2o.b2(), [b2o])
+
+// Assignment to eval or arguments.
+function c1() {
+  return [for (arg of (for (i of [0, 1, 2]) arguments = i)) arg];
+}
+assertDeepEq(c1(), [0, 1, 2]);
+
+function c2() {
+  "use strict";
+  return eval('[for (arg of (for (i of [0, 1, 2]) arguments = i)) arg]');
+}
+assertThrows(c2, SyntaxError);
+
+function c3() {
+  return [for (arg of (for (i of [0, 1, 2]) eval = i)) arg];
+}
+assertDeepEq(c3(), [0, 1, 2]);
+
+function c4() {
+  "use strict";
+  return eval('[for (arg of (for (i of [0, 1, 2]) eval = i)) arg]');
+}
+assertThrows(c4, SyntaxError);
+
+reportCompare(null, null, "test");
diff --git a/js/src/tests/ecma_6/Comprehensions/nested-for-if.js b/js/src/tests/ecma_6/Comprehensions/nested-for-if.js
new file mode 100644
index 000000000..4e3291182
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/nested-for-if.js
@@ -0,0 +1,20 @@
+// For and if clauses can nest without limit in comprehensions.  This is
+// unlike JS 1.8 comprehensions, which can only have one trailing "if"
+// clause.
+
+function* range(start, end) {
+  for (var n = start; n < end; n++)
+    yield n;
+}
+
+function primesBetween6And25() {
+  return [for (n of range(6, 25)) if (n % 2) if (n % 3) if (n % 5) n];
+}
+assertDeepEq(primesBetween6And25(), [7,11,13,17,19,23]);
+
+function countUpToEvens(limit) {
+  return [for (n of range(0, limit)) if (!(n % 2)) for (m of range(0, n)) m]
+}
+assertDeepEq(countUpToEvens(7), [0,1,0,1,2,3,0,1,2,3,4,5]);
+
+reportCompare(null, null, "test");
diff --git a/js/src/tests/ecma_6/Comprehensions/scope.js b/js/src/tests/ecma_6/Comprehensions/scope.js
new file mode 100644
index 000000000..e9083d552
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/scope.js
@@ -0,0 +1,18 @@
+// The identifier of a ComprehensionFor is only bound within its tail.
+
+function t() {
+  var x = [0, 1, 2];
+  return [for (x of x) x*2]
+}
+assertDeepEq(t(), [0, 2, 4]);
+
+// Each iteration should create a fresh binding.  Unfortunately this is
+// not currently the case, but bug 449811 will fix this.
+function t2() {
+  var x = [0, 1, 2];
+  return [for (x of x) ()=>x]
+}
+// FIXME: Should be [0, 1, 2].
+assertDeepEq([for (x of t2()) x()], [2, 2, 2]);
+
+reportCompare(null, null, "test");
diff --git a/js/src/tests/ecma_6/Comprehensions/shell.js b/js/src/tests/ecma_6/Comprehensions/shell.js
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/shell.js
diff --git a/js/src/tests/ecma_6/Comprehensions/sudoku.js b/js/src/tests/ecma_6/Comprehensions/sudoku.js
new file mode 100644
index 000000000..680f55f64
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/sudoku.js
@@ -0,0 +1,168 @@
+/* -*- tab-width: 2; indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+function copy(obj) {
+  var o = {};
+  for (var i in obj)
+    o[i] = obj[i];
+  return o;
+}
+
+Array.prototype.repeat = function (n) {
+  var s = this.constructor();
+  for (var i = 0; i < n; i++)
+    s = s.concat(this);
+  return s;
+}
+
+String.prototype.center = function (w) {
+  var n = this.length;
+  if (w <= n)
+    return this;
+  var m = Math.floor((w - n) / 2);
+  return ' '.repeat(m) + this + ' '.repeat(w - n - m);
+}
+
+Array.prototype.toString = Array.prototype.toSource
+Object.prototype.toString = Object.prototype.toSource
+
+function all(seq) {
+  for (var e of seq)
+    if (!e)
+      return false;
+  return true;
+}
+
+function some(seq) {
+  for (var e of seq)
+    if (e)
+      return e;
+  return false;
+}
+
+function cross(A, B) {
+  return [for (a of A) for (b of B) a+b];
+}
+
+function dict(A) {
+  var d = {};
+  for (var e of A)
+    d[e[0]] = e[1];
+  return d;
+}
+
+function set(A) {
+  var s = [];
+  for (var e of A)
+    if (!s.includes(e))
+      s.push(e);
+  return s;
+}
+
+function zip(A, B) {
+  var z = [];
+  var n = Math.min(A.length, B.length);
+  for (var i = 0; i < n; i++)
+    z.push([A[i], B[i]]);
+  return z;
+}
+
+rows = 'ABCDEFGHI';
+cols = '123456789';
+digits   = '123456789';
+squares  = cross(rows, cols);
+unitlist = [for (c of cols) cross(rows, c)]
+  .concat([for (r of rows) cross(r, cols)])
+  .concat([for (rs of ['ABC','DEF','GHI']) for (cs of ['123','456','789']) cross(rs, cs)]);
+units = dict((for (s of squares)
+                [s, [for (u of unitlist) if (u.includes(s)) u]]));
+
+peers = dict((for (s of squares)
+                [s, set([for (u of units[s]) for (s2 of u) if (s2 != s) s2])]));
+
+// Given a string of 81 digits (or . or 0 or -), return a dict of {cell:values}.
+function parse_grid(grid) {
+  grid = [for (c of grid) if ('0.-123456789'.includes(c)) c];
+  var values = dict((for (s of squares) [s, digits]));
+
+  for (var pair of zip(squares, grid)) {
+    var s = pair[0], d = pair[1];
+    if (digits.includes(d) && !assign(values, s, d))
+      return false;
+  }
+  return values;
+}
+
+// Eliminate all the other values (except d) from values[s] and propagate.
+function assign(values, s, d) {
+  if (all((for (d2 of values[s]) if (d2 != d) eliminate(values, s, d2))))
+    return values;
+  return false;
+}
+
+// Eliminate d from values[s]; propagate when values or places <= 2.
+function eliminate(values, s, d) {
+  if (!values[s].includes(d))
+    return values; // Already eliminated
+  values[s] = values[s].replace(d, '');
+  if (values[s].length == 0)
+    return false;  // Contradiction: removed last value
+  if (values[s].length == 1) {
+    // If there is only one value (d2) left in square, remove it from peers
+    var d2 = values[s][0];
+    if (!all((for (s2 of peers[s]) eliminate(values, s2, d2))))
+      return false;
+  }
+  // Now check the places where d appears in the units of s
+  for (var u of units[s]) {
+    var dplaces = [for (s of u) if (values[s].includes(d)) s];
+    if (dplaces.length == 0)
+      return false;
+    if (dplaces.length == 1)
+	    // d can only be in one place in unit; assign it there
+      if (!assign(values, dplaces[0], d))
+        return false;
+  }
+  return values;
+}
+
+// Used for debugging.
+function print_board(values) {
+  var width = 1 + Math.max.apply(Math, [for (s of squares) values[s].length]);
+  var line = '\n' + ['-'.repeat(width*3)].repeat(3).join('+');
+  for (var r of rows)
+    print([for (c of cols)
+              values[r+c].center(width) + ('36'.includes(c) && '|' || '')]
+          .join('') + ('CF'.includes(r) && line || ''));
+  print('\n');
+}
+
+easy = "..3.2.6..9..3.5..1..18.64....81.29..7.......8..67.82....26.95..8..2.3..9..5.1.3..";
+
+print_board(parse_grid(easy));
+
+// Using depth-first search and constraint propagation, try all possible values.
+function search(values) {
+  if (!values)
+    return false;    // Failed earlier
+  if (all((for (s of squares) values[s].length == 1)))
+    return values;   // Solved!
+
+  // Choose the unfilled square s with the fewest possibilities
+  // XXX Math.min etc. should work with generator expressions and other iterators
+  // XXX Math.min etc. should work on arrays (lists or tuples in Python) as well as numbers
+  var a = [for (s of squares) if (values[s].length > 1) values[s].length + s].sort();
+  var s = a[0].slice(-2);
+
+  return some((for (d of values[s]) search(assign(copy(values), s, d))));
+}
+
+hard = '4.....8.5.3..........7......2.....6.....8.4......1.......6.3.7.5..2.....1.4......';
+
+print_board(search(parse_grid(hard)))
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
diff --git a/js/src/tests/ecma_6/Comprehensions/syntax.js b/js/src/tests/ecma_6/Comprehensions/syntax.js
new file mode 100644
index 000000000..a57b1e6dd
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/syntax.js
@@ -0,0 +1,6 @@
+// "let" is not allowed as an identifier.
+
+assertThrowsInstanceOf(function () { eval('[for (let of y) foo]') }, SyntaxError);
+assertThrowsInstanceOf(function () { eval('(for (let of y) foo)') }, SyntaxError);
+
+reportCompare(null, null, "test");
diff --git a/js/src/tests/ecma_6/Comprehensions/toSource.js b/js/src/tests/ecma_6/Comprehensions/toSource.js
new file mode 100644
index 000000000..5ce1db172
--- /dev/null
+++ b/js/src/tests/ecma_6/Comprehensions/toSource.js
@@ -0,0 +1,14 @@
+/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+assertEq(  function () { g = (for (d of [0]) d); g.next(); }.toSource(),
+         '(function () { g = (for (d of [0]) d); g.next(); })');
+         
+
+assertEq(  function () { return [for (d of [0]) d]; }.toSource(),
+         '(function () { return [for (d of [0]) d]; })');
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);