From 12bcd8b60332e486223e4033cdf3e3a78195d5b2 Mon Sep 17 00:00:00 2001
From: blickly <blickly@google.com>
Date: Thu, 30 Jun 2016 11:37:07 -0700
Subject: [PATCH] Consider `while (true) {...}` loops as infinite loops.
 ------------- Created by MOE: https://github.com/google/moe
 MOE_MIGRATED_REVID=126325051

---
 .../jscomp/ControlFlowAnalysis.java           | 21 +++++++++++--------
 .../NewTypeInferenceES5OrLowerTest.java       |  6 +++---
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/src/com/google/javascript/jscomp/ControlFlowAnalysis.java b/src/com/google/javascript/jscomp/ControlFlowAnalysis.java
index ae261e67379..543315faf2d 100644
--- a/src/com/google/javascript/jscomp/ControlFlowAnalysis.java
+++ b/src/com/google/javascript/jscomp/ControlFlowAnalysis.java
@@ -373,24 +373,27 @@ private void handleIf(Node node) {
   }
 
   private void handleWhile(Node node) {
+    Node cond = node.getFirstChild();
     // Control goes to the first statement if the condition evaluates to true.
-    createEdge(node, Branch.ON_TRUE,
-        computeFallThrough(node.getSecondChild()));
+    createEdge(node, Branch.ON_TRUE, computeFallThrough(cond.getNext()));
 
-    // Control goes to the follow() if the condition evaluates to false.
-    createEdge(node, Branch.ON_FALSE,
-        computeFollowNode(node, this));
+    if (!cond.isTrue()) {
+      // Control goes to the follow() if the condition evaluates to false.
+      createEdge(node, Branch.ON_FALSE, computeFollowNode(node, this));
+    }
     connectToPossibleExceptionHandler(
         node, NodeUtil.getConditionExpression(node));
   }
 
   private void handleDo(Node node) {
+    Node cond = node.getFirstChild();
     // The first edge can be the initial iteration as well as the iterations
     // after.
-    createEdge(node, Branch.ON_TRUE, computeFallThrough(node.getFirstChild()));
-    // The edge that leaves the do loop if the condition fails.
-    createEdge(node, Branch.ON_FALSE,
-        computeFollowNode(node, this));
+    createEdge(node, Branch.ON_TRUE, computeFallThrough(cond));
+    if (!cond.isTrue()) {
+      // The edge that leaves the do loop if the condition fails.
+      createEdge(node, Branch.ON_FALSE, computeFollowNode(node, this));
+    }
     connectToPossibleExceptionHandler(
         node, NodeUtil.getConditionExpression(node));
   }
diff --git a/test/com/google/javascript/jscomp/NewTypeInferenceES5OrLowerTest.java b/test/com/google/javascript/jscomp/NewTypeInferenceES5OrLowerTest.java
index 609f08bfc3d..f2654b5141d 100644
--- a/test/com/google/javascript/jscomp/NewTypeInferenceES5OrLowerTest.java
+++ b/test/com/google/javascript/jscomp/NewTypeInferenceES5OrLowerTest.java
@@ -356,7 +356,7 @@ public void testEmptyBlockPropagation() {
   public void testForLoopInference() {
     typeCheck(LINE_JOINER.join(
         "var x = 5;",
-        "for (;true;) {",
+        "for (;x < 10;) {",
         "  x = 'str';",
         "}",
         "var /** (string|number) */ y = x;",
@@ -365,7 +365,7 @@ public void testForLoopInference() {
 
     typeCheck(LINE_JOINER.join(
         "var x = 5;",
-        "while (true) {",
+        "while (x < 10) {",
         "  x = 'str';",
         "}",
         "(function(/** string */ s){})(x);",
@@ -373,7 +373,7 @@ public void testForLoopInference() {
         NewTypeInference.INVALID_ARGUMENT_TYPE);
 
     typeCheck(LINE_JOINER.join(
-        "while (true) {",
+        "while (true || false) {",
         "  var x = 'str';",
         "}",
         "var /** (string|undefined) */ y = x;",