Add handling of instanceof in NilCheckResover.

PiperOrigin-RevId: 830553619

Author: rluble

translator/src/main/java/com/google/devtools/j2objc/translate/NilCheckResolver.java

@@ -39,6 +39,7 @@
 import com.google.devtools.j2objc.ast.FunctionInvocation;
 import com.google.devtools.j2objc.ast.IfStatement;
 import com.google.devtools.j2objc.ast.InfixExpression;
+import com.google.devtools.j2objc.ast.InstanceofExpression;
 import com.google.devtools.j2objc.ast.LabeledStatement;
 import com.google.devtools.j2objc.ast.MethodDeclaration;
 import com.google.devtools.j2objc.ast.MethodInvocation;
@@ -608,6 +609,15 @@ public boolean visit(InfixExpression node) {
     return true;
   }
 
+  @Override
+  public boolean visit(InstanceofExpression node) {
+    VariableElement maybeNullVar = TreeUtil.getVariableElement(node.getLeftOperand());
+    if (maybeNullVar != null) {
+      setConditionalSafeVars(node, Collections.singleton(maybeNullVar), EMPTY_VARS);
+    }
+    return true;
+  }
+
   private boolean handleConditionalOperator(InfixExpression node, boolean logicalAnd) {
     Set<VariableElement> newSafeVars = new HashSet<>();
     int pushCount = 0;

translator/src/test/java/com/google/devtools/j2objc/translate/AutoboxerTest.java

@@ -635,8 +635,6 @@ public void testUnboxingMethodWithDifferentReturnType() throws IOException {
         + "    }\n"
         + "  }\n"
         + "}", "Test", "Test.m");
-    assertInTranslation(
-        translation,
-        "return [((JavaLangCharacter *) nil_chk((JavaLangCharacter *) o)) charValue];");
+    assertInTranslation(translation, "return [(JavaLangCharacter *) o charValue];");
   }
 }

translator/src/test/java/com/google/devtools/j2objc/translate/CastResolverTest.java

@@ -287,13 +287,9 @@ public void testIfStatementCastChkOptimization() throws IOException {
         "  }",
         "}"), "Test", "Test.m");
     assertNotInTranslation(translation, "cast_chk");
-    assertInTranslation(
-        translation, "return [((JavaLangInteger *) nil_chk(((JavaLangInteger *) o))) intValue];");
-    assertInTranslation(
-        translation, "return [((JavaLangDouble *) nil_chk(((JavaLangDouble *) o))) intValue];");
-    assertInTranslation(
-        translation,
-        "return [((JavaLangCharacter *) nil_chk(((JavaLangCharacter *) o))) charValue];");
+    assertInTranslation(translation, "return [((JavaLangInteger *) o) intValue];");
+    assertInTranslation(translation, "return [((JavaLangDouble *) o) intValue];");
+    assertInTranslation(translation, "return [((JavaLangCharacter *) o) charValue];");
   }
 
   public void testIfStatementCastChkNoOpt() throws IOException {