8322810: Lambda expression types can't be classes

Vicente Romero · Vicente Romero · commit 56468c42bef8 · 2025-05-02T20:44:22.000Z
Reviewed-by: mcimadamore
diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java
@@ -3343,6 +3343,10 @@ TargetInfo getTargetInfo(JCPolyExpression that, ResultInfo resultInfo, List<Type
                                 // do nothing
                             }
                         }
+                        if (bound.tsym != syms.objectType.tsym && (!bound.isInterface() || (bound.tsym.flags() & ANNOTATION) != 0)) {
+                            // bound must be j.l.Object or an interface, but not an annotation
+                            reportIntersectionError(that, "not.an.intf.component", bound);
+                        }
                         bound = types.removeWildcards(bound);
                         components.add(bound);
                     }
@@ -3366,6 +3370,11 @@ TargetInfo getTargetInfo(JCPolyExpression that, ResultInfo resultInfo, List<Type
             return new TargetInfo(currentTarget, lambdaType);
         }
 
+        private void reportIntersectionError(DiagnosticPosition pos, String key, Object... args) {
+             resultInfo.checkContext.report(pos,
+                 diags.fragment(Fragments.BadIntersectionTargetForFunctionalExpr(diags.fragment(key, args))));
+        }
+
         void preFlow(JCLambda tree) {
             attrRecover.doRecovery();
             new PostAttrAnalyzer() {
diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties b/src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties
@@ -337,7 +337,7 @@ compiler.misc.bad.intersection.target.for.functional.expr=\
 
 # 0: symbol or type
 compiler.misc.not.an.intf.component=\
-    component type {0} is not an interface
+    component type {0} is not an interface or java.lang.Object
 
 # 0: kind name, 1: message segment
 compiler.err.invalid.mref=\
diff --git a/test/langtools/tools/javac/diags/examples.not-yet.txt b/test/langtools/tools/javac/diags/examples.not-yet.txt
@@ -145,8 +145,6 @@ compiler.note.multiple.elements                         # needs user code
 compiler.err.preview.feature.disabled.classfile         # preview feature support: needs compilation against classfile
 compiler.warn.preview.feature.use.classfile             # preview feature support: needs compilation against classfile
 compiler.note.preview.plural.additional                 # preview feature support: diag test causes intermittent failures (see JDK-8201498)
-compiler.misc.bad.intersection.target.for.functional.expr  # currently not generated, should be removed?
-compiler.misc.not.an.intf.component
 compiler.warn.declared.using.preview                    # after making sealed classes a final feature there is no other
                                                         # preview feature but we should keep this key for future use just
                                                         # in case
diff --git a/test/langtools/tools/javac/diags/examples/NotAnInterfaceComponent.java b/test/langtools/tools/javac/diags/examples/NotAnInterfaceComponent.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2025, 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
@@ -21,9 +21,9 @@
  * questions.
  */
 
-// key: compiler.misc.not.a.functional.intf.1
+// key: compiler.misc.bad.intersection.target.for.functional.expr
+// key: compiler.misc.not.an.intf.component
 // key: compiler.err.prob.found.req
-// key: compiler.misc.incompatible.abstracts
 
 class NotAnInterfaceComponent {
     Object o = (String & Runnable) ()-> { };
diff --git a/test/langtools/tools/javac/lambda/ClassInIntersectionTypeTest.java b/test/langtools/tools/javac/lambda/ClassInIntersectionTypeTest.java
@@ -0,0 +1,49 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 8322810
+ * @summary Lambda expressions can implement classes
+ * @compile/fail/ref=ClassInIntersectionTypeTest.out -XDrawDiagnostics ClassInIntersectionTypeTest.java
+ */
+
+import java.io.Serializable;
+import java.lang.annotation.Annotation;
+
+public class ClassInIntersectionTypeTest {
+    // test 1
+    void m1() {
+        ClassInIntersectionTypeTest r1 = (ClassInIntersectionTypeTest & Runnable) () -> System.out.println("Hello, World!");
+        ClassInIntersectionTypeTest r2 = (ClassInIntersectionTypeTest & Runnable) ClassInIntersectionTypeTest::run1;
+    }
+
+    static void run1() {}
+
+    // test 2
+    static void foo() {
+        run2(() -> System.out.println("Hello, World!"));
+        run2(ClassInIntersectionTypeTest::run1);
+    }
+
+    static <T extends ClassInIntersectionTypeTest & Runnable> void run2(T t) {
+        t.run();
+    }
+
+    static Class<? extends Annotation> myAnnoType() { return null; }
+    @interface Anno {}
+    @interface Anno2 {}
+
+    Anno anno1 = (Anno & Serializable) ()-> null; // annotations not allowed
+    Anno anno2 = (Serializable & Anno & Anno2) ()-> null; // annotations not allowed
+    Anno anno3 = (Anno & Serializable) ClassInIntersectionTypeTest::myAnnoType; // annotations not allowed
+    Anno anno4 = (Serializable & Anno2 & Anno) ClassInIntersectionTypeTest::myAnnoType; // annotations not allowed
+
+    static void bar() {
+        annotationType(() -> null);
+        annotationType(ClassInIntersectionTypeTest::myAnnoType);
+    }
+
+    static <T extends Anno & Serializable> void annotationType(T t) {
+        t.annotationType();
+    }
+
+    Anno anno5 = ()-> null; // annotations are not functional interfaces
+}
diff --git a/test/langtools/tools/javac/lambda/ClassInIntersectionTypeTest.out b/test/langtools/tools/javac/lambda/ClassInIntersectionTypeTest.out
@@ -0,0 +1,12 @@
+ClassInIntersectionTypeTest.java:14:83: compiler.err.prob.found.req: (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest))
+ClassInIntersectionTypeTest.java:15:83: compiler.err.prob.found.req: (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest))
+ClassInIntersectionTypeTest.java:22:13: compiler.err.prob.found.req: (compiler.misc.infer.no.conforming.assignment.exists: T, (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest)))
+ClassInIntersectionTypeTest.java:23:13: compiler.err.prob.found.req: (compiler.misc.infer.no.conforming.assignment.exists: T, (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest)))
+ClassInIntersectionTypeTest.java:34:40: compiler.err.prob.found.req: (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest.Anno))
+ClassInIntersectionTypeTest.java:35:48: compiler.err.prob.found.req: (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest.Anno))
+ClassInIntersectionTypeTest.java:36:40: compiler.err.prob.found.req: (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest.Anno))
+ClassInIntersectionTypeTest.java:37:48: compiler.err.prob.found.req: (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest.Anno2))
+ClassInIntersectionTypeTest.java:40:23: compiler.err.prob.found.req: (compiler.misc.infer.no.conforming.assignment.exists: T, (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest.Anno)))
+ClassInIntersectionTypeTest.java:41:23: compiler.err.prob.found.req: (compiler.misc.infer.no.conforming.assignment.exists: T, (compiler.misc.bad.intersection.target.for.functional.expr: (compiler.misc.not.an.intf.component: ClassInIntersectionTypeTest.Anno)))
+ClassInIntersectionTypeTest.java:48:18: compiler.err.prob.found.req: (compiler.misc.not.a.functional.intf: ClassInIntersectionTypeTest.Anno)
+11 errors

Original file line number	Diff line number	Diff line change
`@@ -3343,6 +3343,10 @@ TargetInfo getTargetInfo(JCPolyExpression that, ResultInfo resultInfo, List<Type`
`3343`	`3343`	`// do nothing`
`3344`	`3344`	`}`
`3345`	`3345`	`}`
	`3346`	`+ if (bound.tsym != syms.objectType.tsym && (!bound.isInterface() \|\| (bound.tsym.flags() & ANNOTATION) != 0)) {`
	`3347`	`+ // bound must be j.l.Object or an interface, but not an annotation`
	`3348`	`+ reportIntersectionError(that, "not.an.intf.component", bound);`
	`3349`	`+ }`
`3346`	`3350`	`bound = types.removeWildcards(bound);`
`3347`	`3351`	`components.add(bound);`
`3348`	`3352`	`}`
`@@ -3366,6 +3370,11 @@ TargetInfo getTargetInfo(JCPolyExpression that, ResultInfo resultInfo, List<Type`
`3366`	`3370`	`return new TargetInfo(currentTarget, lambdaType);`
`3367`	`3371`	`}`
`3368`	`3372`
	`3373`	`+ private void reportIntersectionError(DiagnosticPosition pos, String key, Object... args) {`
	`3374`	`+ resultInfo.checkContext.report(pos,`
	`3375`	`+ diags.fragment(Fragments.BadIntersectionTargetForFunctionalExpr(diags.fragment(key, args))));`
	`3376`	`+ }`
	`3377`	`+`
`3369`	`3378`	`void preFlow(JCLambda tree) {`
`3370`	`3379`	`attrRecover.doRecovery();`
`3371`	`3380`	`new PostAttrAnalyzer() {`