Support compilation of varargs invocations in SpEL for array subtypes

This commit merges support for compiling SpEL expressions that contain
varargs invocations where the supplied array is a subtype of the
declared varargs array type.

Closes gh-32804

Author: sbrannen

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

@@ -16,13 +16,13 @@
 
 package org.springframework.expression.spel.ast;
 
-import java.lang.reflect.Constructor;
+import java.lang.reflect.Executable;
 import java.lang.reflect.Member;
-import java.lang.reflect.Method;
 import java.util.function.Supplier;
 
 import org.springframework.asm.MethodVisitor;
 import org.springframework.asm.Opcodes;
+import org.springframework.asm.Type;
 import org.springframework.expression.EvaluationException;
 import org.springframework.expression.TypedValue;
 import org.springframework.expression.common.ExpressionUtils;
@@ -33,7 +33,9 @@
 import org.springframework.expression.spel.SpelNode;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 
 /**
  * The common supertype of all AST nodes in a parsed Spring Expression Language
@@ -216,20 +218,37 @@ protected ValueRef getValueRef(ExpressionState state) throws EvaluationException
 	 * @param cf the current codeflow
 	 * @param member the method or constructor for which arguments are being set up
 	 * @param arguments the expression nodes for the expression supplied argument values
+	 * @deprecated As of Spring Framework 6.2, in favor of
+	 * {@link #generateCodeForArguments(MethodVisitor, CodeFlow, Executable, SpelNodeImpl[])}
 	 */
+	@Deprecated(since = "6.2")
 	protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Member member, SpelNodeImpl[] arguments) {
-		String[] paramDescriptors = null;
-		boolean isVarargs = false;
-		if (member instanceof Constructor<?> ctor) {
-			paramDescriptors = CodeFlow.toDescriptors(ctor.getParameterTypes());
-			isVarargs = ctor.isVarArgs();
+		if (member instanceof Executable executable) {
+			generateCodeForArguments(mv, cf, executable, arguments);
 		}
-		else { // Method
-			Method method = (Method)member;
-			paramDescriptors = CodeFlow.toDescriptors(method.getParameterTypes());
-			isVarargs = method.isVarArgs();
-		}
-		if (isVarargs) {
+		throw new IllegalArgumentException(
+				"The supplied member must be an instance of java.lang.reflect.Executable: " + member);
+	}
+
+	/**
+	 * Generate code that handles building the argument values for the specified
+	 * {@link Executable} (method or constructor).
+	 * <p>This method takes into account whether the invoked executable was
+	 * declared to accept varargs, and if it was then the argument values will be
+	 * appropriately packaged into an array.
+	 * @param mv the method visitor where code should be generated
+	 * @param cf the current {@link CodeFlow}
+	 * @param executable the {@link Executable} (method or constructor) for which
+	 * arguments are being set up
+	 * @param arguments the expression nodes for the expression supplied argument
+	 * values
+	 * @since 6.2
+	 */
+	protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Executable executable, SpelNodeImpl[] arguments) {
+		Class<?>[] parameterTypes = executable.getParameterTypes();
+		String[] paramDescriptors = CodeFlow.toDescriptors(parameterTypes);
+
+		if (executable.isVarArgs()) {
 			// The final parameter may or may not need packaging into an array, or nothing may
 			// have been passed to satisfy the varargs and so something needs to be built.
 			int p = 0; // Current supplied argument being processed
@@ -241,13 +260,18 @@ protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Me
 			}
 
 			SpelNodeImpl lastChild = (childCount == 0 ? null : arguments[childCount - 1]);
-			String arrayType = paramDescriptors[paramDescriptors.length - 1];
+			ClassLoader classLoader = executable.getDeclaringClass().getClassLoader();
+			Class<?> lastChildType = (lastChild != null ?
+					loadClassForExitDescriptor(lastChild.getExitDescriptor(), classLoader) : null);
+			Class<?> lastParameterType = parameterTypes[parameterTypes.length - 1];
+
 			// Determine if the final passed argument is already suitably packaged in array
 			// form to be passed to the method
-			if (lastChild != null && arrayType.equals(lastChild.getExitDescriptor())) {
+			if (lastChild != null && lastChildType != null && lastParameterType.isAssignableFrom(lastChildType)) {
 				cf.generateCodeForArgument(mv, lastChild, paramDescriptors[p]);
 			}
 			else {
+				String arrayType = paramDescriptors[paramDescriptors.length - 1];
 				arrayType = arrayType.substring(1); // trim the leading '[', may leave other '['
 				// build array big enough to hold remaining arguments
 				CodeFlow.insertNewArrayCode(mv, childCount - p, arrayType);
@@ -270,6 +294,19 @@ protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Me
 		}
 	}
 
+	@Nullable
+	private static Class<?> loadClassForExitDescriptor(@Nullable String exitDescriptor, ClassLoader classLoader) {
+		if (!StringUtils.hasText(exitDescriptor)) {
+			return null;
+		}
+		String typeDescriptor = exitDescriptor;
+		if (typeDescriptor.startsWith("[") || typeDescriptor.startsWith("L")) {
+			typeDescriptor += ";";
+		}
+		String className = Type.getType(typeDescriptor).getClassName();
+		return ClassUtils.resolveClassName(className, classLoader);
+	}
+
 	/**
 	 * Ask an argument to generate its bytecode and then follow it up
 	 * with any boxing/unboxing/checkcasting to ensure it matches the expected parameter descriptor.