for loop variables are aliased

Author: fglock

MILESTONES.md

@@ -144,7 +144,6 @@
   - `goto` special cases - for `Text::Balanced`.
   - indirect object special cases - for `GetOpt::Long`.
   - Here documents.
-  - Implement aliasing in `for`.
   - Implement localization of regex variables.
 - DBI subsystem
   - Additional methods.
@@ -181,6 +180,7 @@
 - **v2.2.0**: Core modules
   - Perl version is now v5.40.0
   - `for` loop can iterate over multiple values at the same time.
+  - `for` loop variables are aliased.
   - Added `DBI` module with JDBC support.
   - Added `URI::Escape` module.
   - Added `builtin` methods: `inf` `nan` `weaken` `unweaken` `is_weak` `blessed` `refaddr` `reftype` `created_as_string` `created_as_number` `stringify` `ceil` `floor` `indexed` `trim` `is_tainted`.

docs/FEATURE_MATRIX.md

@@ -261,7 +261,7 @@
 - 🚧  **File test operators**: The current implementation only works with file paths, not filehandles or dirhandles.
 - ❌  **File test operators**: Add support for stacked file test operators.
 - ✔️   **Directory operators**: `readdir`, `opendir`, `closedir`, `telldir`, `seekdir`, `rewinddir`, `mkdir`, `rmdir`, `chdir`.
-- ❌  **`for` loop variable**: The `for` loop variable is not an alias to a list element.
+- ✔️   **`for` loop variable**: The `for` loop variable is aliased to list elements.
 - ✔️   **`for` loop variable**: Iterate over multiple values at a time is implemented.
 - ✔️   **loop control operators**: `next`, `last`, `redo` with labels are implemented.
 - ❌  **loop control operators**: `next`, `last`, `redo` with expression are not implemented.

src/main/java/org/perlonjava/astnode/For1Node.java

@@ -12,10 +12,6 @@ public class For1Node extends AbstractNode {
      * This loop creates a new variable scope
      */
     public final boolean useNewScope;
-    /**
-     * The list part of the for loop.
-     */
-    public Node variable;
     /**
      * The variable part of the for loop.
      */
@@ -25,6 +21,10 @@ public class For1Node extends AbstractNode {
      */
     public final Node body;
     public final Node continueBlock;
+    /**
+     * The list part of the for loop.
+     */
+    public Node variable;
     /**
      * the label name for this loop
      */

src/main/java/org/perlonjava/codegen/EmitForeach.java

@@ -4,6 +4,7 @@
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Opcodes;
 import org.perlonjava.astnode.*;
+import org.perlonjava.perlmodule.Warnings;
 import org.perlonjava.runtime.RuntimeContextType;
 
 public class EmitForeach {
@@ -24,17 +25,26 @@ static void emitFor1(EmitterVisitor emitterVisitor, For1Node node) {
                 opNode.operator.equals("$") &&
                 opNode.operand instanceof IdentifierNode idNode &&
                 idNode.name.equals("_")) {
-            int varIndex = emitterVisitor.ctx.symbolTable.getVariableIndex("$_");
-            if (varIndex == -1) {
-                node.variable = new OperatorNode("our", node.variable, node.variable.getIndex());
-            }
+            node.variable = new OperatorNode("our", node.variable, node.variable.getIndex());
         }
 
         // First declare the variables if it's a my/our operator
         if (node.variable instanceof OperatorNode opNode &&
                 (opNode.operator.equals("my") || opNode.operator.equals("our"))) {
+            boolean isWarningEnabled = Warnings.warningManager.isWarningEnabled("redefine");
+            if (isWarningEnabled) {
+                // turn off "masks earlier declaration" warning
+                Warnings.warningManager.setWarningState("redefine", false);
+            }
+            // emit the variable declarations
             node.variable.accept(emitterVisitor.with(RuntimeContextType.VOID));
-            node.variable = ((OperatorNode) node.variable).operand;
+            // rewrite the variable node without the declaration
+            node.variable = opNode.operand;
+
+            if (isWarningEnabled) {
+                // restore warnings
+                Warnings.warningManager.setWarningState("redefine", true);
+            }
         }
 
         // Obtain the iterator for the list
@@ -78,7 +88,7 @@ static void emitFor1(EmitterVisitor emitterVisitor, For1Node node) {
                 // Assign to variable
                 Node varNode = varList.elements.get(i);
                 if (varNode instanceof OperatorNode operatorNode) {
-                    String varName = operatorNode.operator + ((IdentifierNode)operatorNode.operand).name;
+                    String varName = operatorNode.operator + ((IdentifierNode) operatorNode.operand).name;
                     int varIndex = emitterVisitor.ctx.symbolTable.getVariableIndex(varName);
                     emitterVisitor.ctx.logDebug("FOR1 multi var name:" + varName + " index:" + varIndex);
                     mv.visitVarInsn(Opcodes.ASTORE, varIndex);
@@ -91,7 +101,7 @@ static void emitFor1(EmitterVisitor emitterVisitor, For1Node node) {
             mv.visitTypeInsn(Opcodes.CHECKCAST, "org/perlonjava/runtime/RuntimeScalar");
 
             if (node.variable instanceof OperatorNode operatorNode) {
-                String varName = operatorNode.operator + ((IdentifierNode)operatorNode.operand).name;
+                String varName = operatorNode.operator + ((IdentifierNode) operatorNode.operand).name;
                 int varIndex = emitterVisitor.ctx.symbolTable.getVariableIndex(varName);
                 emitterVisitor.ctx.logDebug("FOR1 single var name:" + varName + " index:" + varIndex);
                 mv.visitVarInsn(Opcodes.ASTORE, varIndex);

src/main/java/org/perlonjava/codegen/EmitVariable.java

@@ -3,6 +3,7 @@
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Opcodes;
 import org.perlonjava.astnode.*;
+import org.perlonjava.perlmodule.Warnings;
 import org.perlonjava.runtime.*;
 
 import java.util.ArrayList;
@@ -347,11 +348,13 @@ static void handleMyOperator(EmitterVisitor emitterVisitor, OperatorNode node) {
                     String var = sigil + name;
                     emitterVisitor.ctx.logDebug("MY " + operator + " " + sigil + name);
                     if (emitterVisitor.ctx.symbolTable.getVariableIndexInCurrentScope(var) != -1) {
-                        System.err.println(
-                                emitterVisitor.ctx.errorUtil.errorMessage(node.getIndex(),
-                                        "Warning: \"" + operator + "\" variable "
-                                                + var
-                                                + " masks earlier declaration in same ctx.symbolTable"));
+                        if (Warnings.warningManager.isWarningEnabled("redefine")) {
+                            System.err.println(
+                                    emitterVisitor.ctx.errorUtil.errorMessage(node.getIndex(),
+                                            "Warning: \"" + operator + "\" variable "
+                                                    + var
+                                                    + " masks earlier declaration in same ctx.symbolTable"));
+                        }
                     }
                     int varIndex = emitterVisitor.ctx.symbolTable.addVariable(var, operator, sigilNode);
                     // TODO optimization - SETVAR+MY can be combined

src/main/java/org/perlonjava/perlmodule/Exporter.java

@@ -60,14 +60,14 @@ public static RuntimeList importSymbols(RuntimeArray args, int ctx) {
         RuntimeArray exportOk = GlobalVariable.getGlobalArray(packageScalar + "::EXPORT_OK");
         RuntimeHash exportTags = GlobalVariable.getGlobalHash(packageScalar + "::EXPORT_TAGS");
 
-            // If no specific symbols are requested, default to exporting all symbols in @EXPORT
-            if (args.size() == 0) {
-                if (export != null && export.elements != null) {
-                    args = export;
-                } else {
-                    args = new RuntimeArray();
-                }
+        // If no specific symbols are requested, default to exporting all symbols in @EXPORT
+        if (args.size() == 0) {
+            if (export != null && export.elements != null) {
+                args = export;
+            } else {
+                args = new RuntimeArray();
             }
+        }
 
         String exportLevel = GlobalVariable.getGlobalVariable("Exporter::ExportLevel").toString();
 

src/main/java/org/perlonjava/perlmodule/Warnings.java

@@ -10,7 +10,7 @@
  */
 public class Warnings extends PerlModuleBase {
 
-    private static final WarningFlags warningManager = new WarningFlags();
+    public static final WarningFlags warningManager = new WarningFlags();
 
     /**
      * Constructor for Warnings.

src/main/java/org/perlonjava/runtime/WarningFlags.java

@@ -96,7 +96,7 @@ public void disableWarning(String category) {
      * @param category The name of the warning category.
      * @param state    The state to set (true for enabled, false for disabled).
      */
-    private void setWarningState(String category, boolean state) {
+    public void setWarningState(String category, boolean state) {
         ScopedSymbolTable symbolTable = getCurrentScope();
         if (state) {
             symbolTable.enableWarningCategory(category);