fix: Fix the insertion order for CtStatementListImpl.insertBegin (#4065)

src/main/java/spoon/support/reflect/code/CtStatementListImpl.java

@@ -21,6 +21,7 @@
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.ListIterator;
 
 import static spoon.reflect.ModelElementContainerDefaultCapacities.BLOCK_STATEMENTS_CONTAINER_DEFAULT_CAPACITY;
 import static spoon.reflect.path.CtRole.STATEMENT;
@@ -83,7 +84,10 @@ private void ensureModifiableStatementsList() {
 	@Override
 	public <T extends CtStatementList> T insertBegin(CtStatementList statements) {
 		ensureModifiableStatementsList();
-		for (CtStatement statement : statements.getStatements()) {
+		List<CtStatement> list = statements.getStatements();
+		ListIterator listIterator = list.listIterator(list.size());
+		while (listIterator.hasPrevious()) {
+			CtStatement statement = (CtStatement) listIterator.previous();
 			statement.setParent(this);
 			this.addStatement(0, statement);
 		}

src/test/java/spoon/test/ctStatementList/CtStatementListTest.java

@@ -0,0 +1,49 @@
+package spoon.test.ctStatementList;
+
+import org.junit.jupiter.api.Test;
+import spoon.Launcher;
+import spoon.reflect.code.CtStatement;
+import spoon.reflect.code.CtStatementList;
+import spoon.reflect.factory.Factory;
+import spoon.support.reflect.code.CtStatementListImpl;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.CoreMatchers.is;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class CtStatementListTest {
+
+    @Test
+    void testInsertBeginWithListOfStatements() {
+        // contract: insertBegin adds a list of statements at the beginning of the statementList
+
+        // arrange
+        Factory factory = new Launcher().getFactory();
+
+        CtStatement initialStatement = factory.Code().createCodeSnippetStatement("int preexisting = 42;").compile();
+
+        CtStatement firstStatementToBeInserted = factory.Code().createCodeSnippetStatement("int first = 1;").compile();
+        CtStatement secondStatementToBeInserted = factory.Code().createCodeSnippetStatement("int second = 2;").compile();
+
+        CtStatementList mainStatementList = new CtStatementListImpl<CtStatement>();
+        mainStatementList.addStatement(initialStatement);
+
+        CtStatementList statementListToBeAddedToTheMainList = new CtStatementListImpl<CtStatement>();
+        statementListToBeAddedToTheMainList.addStatement(firstStatementToBeInserted);
+        statementListToBeAddedToTheMainList.addStatement(secondStatementToBeInserted);
+
+        // act
+        mainStatementList.insertBegin(statementListToBeAddedToTheMainList);
+
+        // assert
+        CtStatement statementAtTheBeginningAfterInsertion = mainStatementList.getStatements().get(0);
+        CtStatement secondStatementAtTheBeginningOfTheListAfterInsertion = mainStatementList.getStatements().get(1);
+
+        assertEquals(firstStatementToBeInserted, statementAtTheBeginningAfterInsertion);
+        assertEquals(secondStatementToBeInserted, secondStatementAtTheBeginningOfTheListAfterInsertion);
+
+        assertThat(firstStatementToBeInserted.getParent(), is(mainStatementList));
+        assertThat(secondStatementToBeInserted.getParent(), is(mainStatementList));
+    }
+}