From cdf064187bd660fad4b5b65b12be5e2a043779eb Mon Sep 17 00:00:00 2001
From: dimvar <dimvar@google.com>
Date: Fri, 15 Jul 2016 11:36:35 -0700
Subject: [PATCH] [NTI] Improvements to handling of truthy types.

Fixes github issue #1857
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=127561403
---
 .../javascript/jscomp/NewTypeInference.java   |  2 +-
 .../javascript/jscomp/newtypes/JSType.java    |  3 +--
 .../jscomp/NewTypeInferenceTest.java          | 22 ++++++++++++++++++-
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/com/google/javascript/jscomp/NewTypeInference.java b/src/com/google/javascript/jscomp/NewTypeInference.java
index dc357c014bd..ac349aa149f 100644
--- a/src/com/google/javascript/jscomp/NewTypeInference.java
+++ b/src/com/google/javascript/jscomp/NewTypeInference.java
@@ -1600,7 +1600,7 @@ private EnvTypePair analyzeInstanceofFwd(
     EnvTypePair objPair, ctorPair;
 
     // First, evaluate ignoring the specialized context
-    objPair = analyzeExprFwd(obj, inEnv);
+    objPair = analyzeExprFwd(obj, inEnv, JSType.TOP_OBJECT);
     JSType objType = objPair.type;
     if (!objType.isTop()
         && !objType.isUnknown()
diff --git a/src/com/google/javascript/jscomp/newtypes/JSType.java b/src/com/google/javascript/jscomp/newtypes/JSType.java
index b35a9c38975..a291e9325b3 100644
--- a/src/com/google/javascript/jscomp/newtypes/JSType.java
+++ b/src/com/google/javascript/jscomp/newtypes/JSType.java
@@ -28,7 +28,6 @@
 import com.google.javascript.rhino.Node;
 import com.google.javascript.rhino.ObjectTypeI;
 import com.google.javascript.rhino.TypeI;
-
 import java.util.Collection;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -749,7 +748,7 @@ boolean unifyWithSubtype(JSType other, List<String> typeParameters,
         && typeParameters.contains(getTypeVar())) {
       updateTypemap(typeMultimap, getTypeVar(), other);
       return true;
-    } else if (other.isUnknown()) {
+    } else if (other.isUnknown() || other.isTrueOrTruthy()) {
       return true;
     } else if (other.isTop()) {
       // T|number doesn't unify with TOP
diff --git a/test/com/google/javascript/jscomp/NewTypeInferenceTest.java b/test/com/google/javascript/jscomp/NewTypeInferenceTest.java
index e2b6bc52842..6a45fff6fa0 100644
--- a/test/com/google/javascript/jscomp/NewTypeInferenceTest.java
+++ b/test/com/google/javascript/jscomp/NewTypeInferenceTest.java
@@ -17218,7 +17218,7 @@ public void testMeetingWithTruthyFalsy() {
         "function f(x) { if (!x) { return /** @type {number} */ (x); } }");
   }
 
-  public void testPropAccessOnTruthy() {
+  public void testUsingTruthy() {
     typeCheck(LINE_JOINER.join(
         "function f(/** !Function */ x) {",
         "  return x.superClass_ ? x.superClass_.constructor : null;",
@@ -17228,6 +17228,26 @@ public void testPropAccessOnTruthy() {
         "function f(/** !Function */ x) {",
         "  if (x.superClass_) { x.superClass_.constructor = null; }",
         "}"));
+
+    typeCheck(LINE_JOINER.join(
+        "function g(x) { var /** !Object */ y = x; }",
+        "function f(x) {",
+        "  if (!x) return null;",
+        "  g(x);",
+        "  return x instanceof Array;",
+        "}"));
+
+    typeCheck(LINE_JOINER.join(
+        "function f(x) {",
+        "  if (!x) return null;",
+        "  forEach(x, function(y){});",
+        "}",
+        "/**",
+        " * @param {!Array<T>} arr",
+        " * @param {function(T)} cb",
+        " * @template T",
+        " */",
+        "function forEach(arr, cb) {}"));
   }
 
   public void testIObjectExternMissing() {