Nullability fine-tuning around declaration inconsistencies

Issue: SPR-15720
Issue: SPR-15792

spring-expression/src/main/java/org/springframework/expression/spel/ast/CompoundExpression.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@ import org.springframework.expression.TypedValue;
 import org.springframework.expression.spel.CodeFlow;
 import org.springframework.expression.spel.ExpressionState;
 import org.springframework.expression.spel.SpelEvaluationException;
+import org.springframework.lang.Nullable;
 
 /**
  * Represents a DOT separated expression sequence, such as 'property1.property2.methodOne()'
@@ -91,7 +92,7 @@ public class CompoundExpression extends SpelNodeImpl {
 	}
 
 	@Override
-	public void setValue(ExpressionState state, Object value) throws EvaluationException {
+	public void setValue(ExpressionState state, @Nullable Object value) throws EvaluationException {
 		getValueRef(state).setValue(value);
 	}
 

spring-expression/src/main/java/org/springframework/expression/spel/ast/OperatorInstanceof.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,8 @@ import org.springframework.expression.spel.ExpressionState;
 import org.springframework.expression.spel.SpelEvaluationException;
 import org.springframework.expression.spel.SpelMessage;
 import org.springframework.expression.spel.support.BooleanTypedValue;
-
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * The operator 'instanceof' checks if an object is of the class specified in the right
@@ -36,8 +37,10 @@ import org.springframework.expression.spel.support.BooleanTypedValue;
  */
 public class OperatorInstanceof extends Operator {
 
+	@Nullable
 	private Class<?> type;
 	
+
 	public OperatorInstanceof(int pos, SpelNodeImpl... operands) {
 		super("instanceof", pos, operands);
 	}
@@ -47,8 +50,8 @@ public class OperatorInstanceof extends Operator {
 	 * Compare the left operand to see it is an instance of the type specified as the
 	 * right operand. The right operand must be a class.
 	 * @param state the expression state
-	 * @return true if the left operand is an instanceof of the right operand, otherwise
-	 *         false
+	 * @return {@code true} if the left operand is an instanceof of the right operand,
+	 * otherwise {@code false}
 	 * @throws EvaluationException if there is a problem evaluating the expression
 	 */
 	@Override
@@ -58,7 +61,7 @@ public class OperatorInstanceof extends Operator {
 		TypedValue right = rightOperand.getValueInternal(state);
 		Object leftValue = left.getValue();
 		Object rightValue = right.getValue();
-		BooleanTypedValue result = null;
+		BooleanTypedValue result;
 		if (rightValue == null || !(rightValue instanceof Class)) {
 			throw new SpelEvaluationException(getRightOperand().getStartPosition(),
 					SpelMessage.INSTANCEOF_OPERATOR_NEEDS_CLASS_OPERAND,
@@ -89,6 +92,7 @@ public class OperatorInstanceof extends Operator {
 	public void generateCode(MethodVisitor mv, CodeFlow cf) {
 		getLeftOperand().generateCode(mv, cf);
 		CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor());
+		Assert.state(this.type != null, "No type available");
 		if (this.type.isPrimitive()) {
 			// always false - but left operand code always driven
 			// in case it had side effects
@@ -96,7 +100,7 @@ public class OperatorInstanceof extends Operator {
 			mv.visitInsn(ICONST_0); // value of false
 		} 
 		else {
-			mv.visitTypeInsn(INSTANCEOF,Type.getInternalName(this.type));
+			mv.visitTypeInsn(INSTANCEOF, Type.getInternalName(this.type));
 		}
 		cf.pushDescriptor(this.exitTypeDescriptor);
 	}

spring-expression/src/main/java/org/springframework/expression/spel/ast/TypeReference.java

@@ -24,6 +24,7 @@ import org.springframework.expression.EvaluationException;
 import org.springframework.expression.TypedValue;
 import org.springframework.expression.spel.CodeFlow;
 import org.springframework.expression.spel.ExpressionState;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -35,15 +36,16 @@ public class TypeReference extends SpelNodeImpl {
 
 	private final int dimensions;
 
+	@Nullable
 	private transient Class<?> type;
 
 
 	public TypeReference(int pos, SpelNodeImpl qualifiedId) {
-		this(pos,qualifiedId,0);
+		this(pos, qualifiedId, 0);
 	}
 
 	public TypeReference(int pos, SpelNodeImpl qualifiedId, int dims) {
-		super(pos,qualifiedId);
+		super(pos, qualifiedId);
 		this.dimensions = dims;
 	}
 
@@ -99,6 +101,7 @@ public class TypeReference extends SpelNodeImpl {
 	@Override
 	public void generateCode(MethodVisitor mv, CodeFlow cf) {
 		// TODO Future optimization - if followed by a static method call, skip generating code here
+		Assert.state(this.type != null, "No type available");
 		if (this.type.isPrimitive()) {
 			if (this.type == Integer.TYPE) {
 				mv.visitFieldInsn(GETSTATIC, "java/lang/Integer", "TYPE", "Ljava/lang/Class;");

spring-expression/src/main/java/org/springframework/expression/spel/ast/ValueRef.java

@@ -68,7 +68,7 @@ public interface ValueRef {
 		}
 
 		@Override
-		public void setValue(Object newValue) {
+		public void setValue(@Nullable Object newValue) {
 			// The exception position '0' isn't right but the overhead of creating
 			// instances of this per node (where the node is solely for error reporting)
 			// would be unfortunate.
@@ -102,7 +102,7 @@ public interface ValueRef {
 		}
 
 		@Override
-		public void setValue(Object newValue) {
+		public void setValue(@Nullable Object newValue) {
 			throw new SpelEvaluationException(this.node.pos, SpelMessage.NOT_ASSIGNABLE, this.node.toStringAST());
 		}
 

spring-expression/src/main/java/org/springframework/expression/spel/support/StandardEvaluationContext.java

@@ -157,6 +157,7 @@ public class StandardEvaluationContext implements EvaluationContext {
 	}
 
 	@Override
+	@Nullable
 	public BeanResolver getBeanResolver() {
 		return this.beanResolver;
 	}