Fix stepping in for-loops.

test/mjsunit/es6/debug-stepnext-for.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-debug-as debug --harmony
+
+Debug = debug.Debug;
+var break_count = 0
+var exception = null;
+var log = []
+
+var s = 0;
+var a = [1, 2, 3];
+var i = 0;
+
+function f() {
+  "use strict";
+  debugger;                      // Break a
+  var j;                         // Break b
+
+  for (var i in null) {          // Break c
+    s += a[i];
+  }
+
+  for (j in null) {              // Break d
+    s += a[j];
+  }
+
+  for (var i in a) {             // Break e
+    s += a[i];                   // Break E
+  }
+
+  for (j in a) {                 // Break f
+    s += a[j];                   // Break F
+  }
+
+  for (let i in a) {             // Break g
+    s += a[i];                   // Break G
+  }
+
+  for (var i of a) {             // Break h
+    s += i;                      // Break H
+  }
+
+  for (j of a) {                 // Break i
+    s += j;                      // Break I
+  }
+
+  for (let i of a) {             // Break j
+    s += i;                      // Break J
+  }
+
+  for (var i = 0; i < 3; i++) {  // Break k
+    s += a[i];                   // Break K
+  }
+
+  for (j = 0; j < 3; j++) {      // Break l
+    s += a[j];                   // Break L
+  }
+
+  // TODO(yangguo): add test case for for-let.
+}                                // Break y
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var line = exec_state.frame(0).sourceLineText();
+    var col = exec_state.frame(0).sourceColumn();
+    print(line);
+    var match = line.match(/\/\/ Break (\w)$/);
+    assertEquals(2, match.length);
+    log.push(match[1] + col);
+    exec_state.prepareStep(Debug.StepAction.StepNext, 1);
+    break_count++;
+  } catch (e) {
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+f();
+Debug.setListener(null);         // Break z
+
+print(JSON.stringify(log));
+// The let declaration differs from var in that the loop variable
+// is declared in every iteration.
+var expected = [
+  // Entry
+  "a2","b2",
+  // Empty for-in-var: var decl, get enumerable
+  "c7","c16",
+  // Empty for-in: get enumerable
+  "d12",
+  // For-in-var: var decl, get enumerable, assign, body, assign, body, ...
+  "e7","e16","e11","E4","e11","E4","e11","E4",
+  // For-in: get enumerable, assign, body, assign, body, ...
+  "f12","f7","F4","f7","F4","f7","F4",
+  // For-in-let: get enumerable, assign new let, body, assign new let, ...
+  "g16","g7","G4","g7","G4","g7","G4",
+  // For-of-var: var decl, next(), body, next(), body, ...
+  "h7","h16","H4","h16","H4","h16","H4","h16",
+  // For-of: next(), body, next(), body, ...
+  "i12","I4","i12","I4","i12","I4","i12",
+  // For-of-let: next(), assign new let, body, next(), assign new let, ...
+  "j16","j7","J4","j16","j7","J4","j16","j7","J4","j16",
+  // For-var: var decl, condition, body, next, condition, body, ...
+  "k7","k20","K4","k23","k20","K4","k23","k20","K4","k23","k20",
+  // For: init, condition, body, next, condition, body, ...
+  "l11","l16","L4","l19","l16","L4","l19","l16","L4","l19","l16",
+  // Exit.
+  "y0","z0",
+]
+
+assertArrayEquals(expected, log);
+assertEquals(48, s);
+assertNull(exception);