8341408: Implement JEP 488: Primitive Types in Patterns, instanceof, and switch (Second Preview)

Reviewed-by: vromero, jlahoda

Author: biboudis

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TransPatterns.java

@@ -199,7 +199,27 @@ protected TransPatterns(Context context) {
 
     @Override
     public void visitTypeTest(JCInstanceOf tree) {
-        if (tree.pattern instanceof JCPattern pattern) {
+        // Translates regular instanceof type operation to instanceof pattern operator when
+        // the expression was originally T but was subsequently erased to Object.
+        //
+        // $expr instanceof $primitiveType
+        // =>
+        // $expr instanceof T $temp && $temp instanceof $primitiveType
+        if (tree.erasedExprOriginalType!=null && !types.isSameType(tree.expr.type, tree.erasedExprOriginalType)) {
+            BindingSymbol temp = new BindingSymbol(Flags.FINAL | Flags.SYNTHETIC,
+                    names.fromString("temp" + variableIndex++ + target.syntheticNameChar()),
+                    tree.erasedExprOriginalType,
+                    currentMethodSym);
+
+            JCVariableDecl tempDecl = make.at(tree.pos()).VarDef(temp, null);
+
+            JCTree resultExpr =
+                    makeBinary(Tag.AND,
+                            make.TypeTest(tree.expr, make.BindingPattern(tempDecl).setType(tree.erasedExprOriginalType)).setType(syms.booleanType),
+                            make.TypeTest(make.Ident(tempDecl), tree.pattern).setType(syms.booleanType));
+
+            result = translate(resultExpr);
+        } else if (tree.pattern instanceof JCPattern pattern) {
             //first, resolve any record patterns:
             JCExpression extraConditions = null;
             if (pattern instanceof JCRecordPattern recordPattern) {

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TransTypes.java

@@ -813,8 +813,7 @@ public void visitSwitch(JCSwitch tree) {
         Type selsuper = types.supertype(tree.selector.type);
         boolean enumSwitch = selsuper != null &&
             selsuper.tsym == syms.enumSym;
-        Type target = enumSwitch ? erasure(tree.selector.type) : syms.intType;
-        tree.selector = translate(tree.selector, target);
+        tree.selector = translate(tree.selector, erasure(tree.selector.type));
         tree.cases = translateCases(tree.cases);
         result = tree;
     }
@@ -852,8 +851,7 @@ public void visitSwitchExpression(JCSwitchExpression tree) {
         Type selsuper = types.supertype(tree.selector.type);
         boolean enumSwitch = selsuper != null &&
             selsuper.tsym == syms.enumSym;
-        Type target = enumSwitch ? erasure(tree.selector.type) : syms.intType;
-        tree.selector = translate(tree.selector, target);
+        tree.selector = translate(tree.selector, erasure(tree.selector.type));
         tree.cases = translate(tree.cases, tree.type);
         tree.type = erasure(tree.type);
         result = retype(tree, tree.type, pt);
@@ -1067,8 +1065,14 @@ public void visitTypeCast(JCTypeCast tree) {
     }
 
     public void visitTypeTest(JCInstanceOf tree) {
-        tree.expr = translate(tree.expr, null);
         tree.pattern = translate(tree.pattern, null);
+        if (tree.pattern.type.isPrimitive()) {
+            tree.erasedExprOriginalType = erasure(tree.expr.type);
+            tree.expr = translate(tree.expr, null);
+        }
+        else {
+            tree.expr = translate(tree.expr, null);
+        }
         result = tree;
     }
 

src/jdk.compiler/share/classes/com/sun/tools/javac/tree/JCTree.java

@@ -2272,6 +2272,8 @@ public static class JCInstanceOf extends JCExpression implements InstanceOfTree
         /**{@code true} if this instanceof test should have
          * value {@code true} when the {@code expr} is {@code null}.*/
         public boolean allowNull;
+        public Type erasedExprOriginalType;
+
         protected JCInstanceOf(JCExpression expr, JCTree pattern) {
             this.expr = expr;
             this.pattern = pattern;

test/langtools/tools/javac/patterns/PrimitiveTypesInTestingContextErasure.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+/*
+ * @test
+ * @bug 8341408
+ * @summary Compiler Implementation for Primitive types in patterns, instanceof, and switch (Second Preview)
+ * @enablePreview
+ */
+
+import java.util.List;
+
+public class PrimitiveTypesInTestingContextErasure {
+    public static void main(String[] args) {
+        erasureSwitch();
+        erasureInstanceofTypeComparisonOperator();
+        erasureInstanceofPatternMatchingOperator();
+
+        pollutedInstanceofPatternMatchingOperatorReference();
+        pollutedInstanceofPatternMatchingOperator();
+        pollutedInstanceofTypeComparisonOperator();
+        pollutedSwitch();
+    }
+
+    public static void erasureSwitch() {
+        List<Short> ls = List.of((short) 42);
+        Short s = 42;
+
+        assertTrue(switch(ls.get(0)) {
+            case int _ -> true;                  // Short to int
+            default -> false;
+        });
+    }
+
+    public static void erasureInstanceofTypeComparisonOperator() {
+        List<Short> ls = List.of((short) 42);
+
+        assertTrue(ls.get(0) instanceof int);   // Short to int
+    }
+
+    public static void erasureInstanceofPatternMatchingOperator() {
+        List<Short> ls = List.of((short) 42);
+
+        assertTrue(ls.get(0) instanceof int i); // Short to int
+    }
+
+    public static void pollutedInstanceofPatternMatchingOperator() {
+        List<Short> ls = (List) List.of("42");
+
+        assertTrue(!(ls.get(0) instanceof int i));
+    }
+
+    public static void pollutedInstanceofTypeComparisonOperator() {
+        List<Short> ls = (List) List.of("42");
+
+        assertTrue(!(ls.get(0) instanceof int));
+    }
+
+    public static void pollutedInstanceofPatternMatchingOperatorReference() {
+        List<Short> ls = (List) List.of("42");
+
+        assertTrue(!(ls.get(0) instanceof Short));
+    }
+
+    public static void pollutedSwitch() {
+        List<Short> ls = (List) List.of("42");
+
+        try {
+            var res = switch(ls.get(0)) {
+                case int _ -> true;
+                default -> false;
+            };
+            throw new AssertionError("Expected: ClassCastException");
+        } catch (ClassCastException e) {
+            ;
+        }
+    }
+
+    static void assertTrue(boolean actual) {
+        if (!actual) {
+            throw new AssertionError("Expected: true, but got false");
+        }
+    }
+}