Fix SpEL generated code for default method invocation

Closes gh-25706

Author: aclement

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

@@ -347,7 +347,8 @@ public void generateCode(MethodVisitor mv, CodeFlow cf) {
 		}
 
 		generateCodeForArguments(mv, cf, method, this.children);
-		mv.visitMethodInsn((isStaticMethod ? INVOKESTATIC : INVOKEVIRTUAL), classDesc, method.getName(),
+		mv.visitMethodInsn((isStaticMethod ? INVOKESTATIC : (method.isDefault() ? INVOKEINTERFACE : INVOKEVIRTUAL)),
+				classDesc, method.getName(),
 				CodeFlow.createSignatureDescriptor(method), method.getDeclaringClass().isInterface());
 		cf.pushDescriptor(this.exitTypeDescriptor);
 

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

@@ -5159,7 +5159,7 @@ private void assertGetValueFail(Expression expression) {
 		assertThatExceptionOfType(Exception.class).isThrownBy(expression::getValue);
 	}
 
-	private void assertIsCompiled(Expression expression) {
+	public static void assertIsCompiled(Expression expression) {
 		try {
 			Field field = SpelExpression.class.getDeclaredField("compiledAst");
 			field.setAccessible(true);

spring-expression/src/test/java/org/springframework/expression/spel/standard/SpelCompilerTests.java

@@ -22,15 +22,18 @@
 
 import org.springframework.core.Ordered;
 import org.springframework.expression.Expression;
+import org.springframework.expression.spel.SpelCompilationCoverageTests;
 import org.springframework.expression.spel.SpelCompilerMode;
 import org.springframework.expression.spel.SpelParserConfiguration;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
  * Tests for the {@link SpelCompiler}.
  *
  * @author Sam Brannen
+ * @author Andy Clement
  * @since 5.1.14
  */
 class SpelCompilerTests {
@@ -55,5 +58,60 @@ public int getOrder() {
 			return 42;
 		}
 	}
+	
+	@Test // gh-25706
+	void defaultMethodInvocation() {
+		SpelParserConfiguration config = new SpelParserConfiguration(SpelCompilerMode.IMMEDIATE, null);
+		SpelExpressionParser parser = new SpelExpressionParser(config);
+
+		StandardEvaluationContext context = new StandardEvaluationContext();
+		Item item = new Item();
+		context.setRootObject(item);
+
+		Expression expression = parser.parseExpression("#root.isEditable2()");
+		assertThat(SpelCompiler.compile(expression)).isFalse();
+		assertThat(expression.getValue(context)).isEqualTo(false);
+		assertThat(SpelCompiler.compile(expression)).isTrue();
+		SpelCompilationCoverageTests.assertIsCompiled(expression);
+		assertThat(expression.getValue(context)).isEqualTo(false);
+
+		context.setVariable("user", new User());
+		expression = parser.parseExpression("#root.isEditable(#user)");
+		assertThat(SpelCompiler.compile(expression)).isFalse();
+		assertThat(expression.getValue(context)).isEqualTo(true);
+		assertThat(SpelCompiler.compile(expression)).isTrue();
+		SpelCompilationCoverageTests.assertIsCompiled(expression);
+		assertThat(expression.getValue(context)).isEqualTo(true);
+	}
+	
+	public static class User {
+		boolean isAdmin() { 
+			return true; 
+		}
+	}
+	
+	public static class Item implements Editable {
+	    // some fields
+	    private String someField = "";
+
+	    // some getters and setters
+
+	   @Override
+	   public boolean hasSomeProperty() {
+	       return someField != null;
+	    }
+	}
+
+	public interface Editable {
+	   default boolean isEditable(User user) {
+	        return user.isAdmin() && hasSomeProperty();
+	   }
+
+	   default boolean isEditable2() {
+		   return false;
+	   }
+
+	   boolean hasSomeProperty();
+	}
 
 }