Review

Possible null pointer dereference of firstArgument variable.

• missing/condition/null_check

com/google/javascript/jscomp/TightenTypes$NativeCallFunctionCall.java

getAssignments(ConcreteScope)

class TightenTypes.Action {
    /** Returns all assignments that may occur by this action. */
    Collection<Assignment> getAssignments(ConcreteScope scope);
}

class TightenTypes.VariableAssignAction {
    public Collection<Assignment> getAssignments(ConcreteScope scope) {
      return Lists.newArrayList(
          new Assignment(slot, inferConcreteType(scope, expression)));
    }
}

class TightenTypes.PropertyAssignAction {
    /**
     * Returns all assignments that could occur as a result of this property
     * assign action. Each type in the receiver is checked for a property
     * {@code propName}, and if that property exists, it is assigned the type
     * of {@code expression}.
     */
    public Collection<Assignment> getAssignments(ConcreteScope scope) {
      ConcreteType recvType = inferConcreteType(scope, receiver);
      ConcreteType exprType = inferConcreteType(scope, expression);

      List<Assignment> assigns = Lists.newArrayList();
      for (StaticSlot<ConcreteType> prop
           : recvType.getPropertySlots(propName)) {
        assigns.add(new Assignment((ConcreteSlot) prop, exprType));
      }
      return assigns;
    }
}

class TightenTypes.ExternFunctionCall {
    public Collection<Assignment> getAssignments(ConcreteScope scope) {
      return getFunctionCallAssignments(inferConcreteType(scope, receiver),
                                        thisType, argTypes);
    }
}

class TightenTypes.FunctionCall {
    public Collection<Assignment> getAssignments(ConcreteScope scope) {
      ConcreteType thisType = ConcreteType.NONE;
      ConcreteType recvType = inferConcreteType(scope, receiver);

      // If a property name was specified, then the receiver is actually the
      // type of this and the actual receiver is the type of that property.
      if (propName != null) {
        thisType = recvType;
        recvType = thisType.getPropertyType(propName);
      }

      if (recvType.isAll()) {
        // TODO(user): ensure that this will trigger for code like
        // functions[3]();
        throw new AssertionError(
            "Found call on all type, which makes tighten types useless.");
      }

      // If this is a call to new, then a new instance of the receiver is
      // created and passed in as the value of this.
      if (isNewCall) {
        thisType = ConcreteType.NONE;
        for (ConcreteInstanceType instType
             : recvType.getFunctionInstanceTypes()) {
          thisType = thisType.unionWith(instType);
        }
        boolean added = allInstantiatedTypes.add(thisType);
        if (added) {
          // A new type instance invalidates the cached type intersections.
          typeIntersectionMemos.clear();
        }
      }

      List<ConcreteType> argTypes = Lists.newArrayList();
      for (Node arg = firstArgument; arg != null; arg = arg.getNext()) {
        argTypes.add(inferConcreteType(scope, arg));
      }

      return getFunctionCallAssignments(recvType, thisType, argTypes);
    }
}

class TightenTypes.NativeCallFunctionCall {
    public Collection<Assignment> getAssignments(ConcreteScope scope) {
      ConcreteType thisType = (firstArgument != null)
          ? inferConcreteType(scope, firstArgument)
          : getTopScope().getTypeOfThis();
      ConcreteType recvType = inferConcreteType(scope, receiver);

      if (recvType instanceof ConcreteInstanceType &&
          ((ConcreteInstanceType) recvType).isFunctionPrototype()) {
        recvType = thisType.getPropertyType(propName);
      }
      List<ConcreteType> argTypes = Lists.newArrayList();
      // Skip the first argument for call() as it is the 'this' object.
      for (Node arg = firstArgument.getNext();
           arg != null;
           arg = arg.getNext()) {
        argTypes.add(inferConcreteType(scope, arg));
      }
      return getFunctionCallAssignments(recvType, thisType, argTypes);
    }

}