Throw exception for failure to set property as index in SpEL

Prior to this commit, the Indexer in the Spring Expression Language
(SpEL) silently ignored a failure to set a property via the indexed
property syntax (['<property name>'] = <new value>) – for example, if
property write access was disabled in the EvaluationContext.

This commit addresses this issue by properly throwing a
SpelEvaluationException in PropertyIndexingValueRef.setValue(Object) if
the property could not be set.

Closes gh-33310

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

@@ -630,6 +630,8 @@ public class Indexer extends SpelNodeImpl {
 				throw new SpelEvaluationException(getStartPosition(), ex,
 						SpelMessage.EXCEPTION_DURING_PROPERTY_WRITE, this.name, ex.getMessage());
 			}
+			throw new SpelEvaluationException(getStartPosition(),
+					SpelMessage.INDEXING_NOT_SUPPORTED_FOR_TYPE, this.targetObjectTypeDescriptor.toString());
 		}
 
 		@Override

spring-expression/src/test/java/org/springframework/expression/spel/PropertyAccessTests.java

@@ -189,6 +189,10 @@ class PropertyAccessTests extends AbstractExpressionTests {
 		assertThatSpelEvaluationException()
 				.isThrownBy(() -> parser.parseExpression("name='p3'").getValue(context, target))
 				.extracting(SpelEvaluationException::getMessageCode).isEqualTo(SpelMessage.PROPERTY_OR_FIELD_NOT_WRITABLE);
+
+		assertThatSpelEvaluationException()
+				.isThrownBy(() -> parser.parseExpression("['name']='p4'").getValue(context, target))
+				.extracting(SpelEvaluationException::getMessageCode).isEqualTo(SpelMessage.INDEXING_NOT_SUPPORTED_FOR_TYPE);
 	}
 
 	@Test