JS backend: added @Nullable to JsNameRef#getName and added assertion to get more information for reproduce #EA-66032

js/js.dart-ast/src/com/google/dart/compiler/backend/js/ast/JsNameRef.java

@@ -7,6 +7,7 @@ package com.google.dart.compiler.backend.js.ast;
 import com.google.dart.compiler.common.Symbol;
 import com.google.dart.compiler.util.AstUtil;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 /**
  * Represents a JavaScript expression that references a name.
@@ -43,6 +44,7 @@ public final class JsNameRef extends JsExpressionImpl implements HasName {
         return (name == null) ? ident : name.getIdent();
     }
 
+    @Nullable
     @Override
     public JsName getName() {
         return name;

js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/TranslationUtils.java

@@ -248,9 +248,10 @@ public final class TranslationUtils {
 
         JsExpression thenExpression = ensureNotNull.getThenExpression();
         if (thenExpression instanceof JsNameRef) {
-            // associate (cache) ensureNotNull expression to new TemporaryConstVariable with same name.
-            context.associateExpressionToLazyValue(ensureNotNull,
-                                                   new TemporaryConstVariable(((JsNameRef) thenExpression).getName(), ensureNotNull));
+            JsName name = ((JsNameRef) thenExpression).getName();
+            assert name != null : "Unexpected state: getName() returned null for `" +thenExpression + "`, ensureNotNull: "+ ensureNotNull;
+            // associate(cache) ensureNotNull expression to new TemporaryConstVariable with same name.
+            context.associateExpressionToLazyValue(ensureNotNull, new TemporaryConstVariable(name, ensureNotNull));
         }
 
         return ensureNotNull;