8254784: javac should reject records with @SafeVarargs applied to varargs record component

Reviewed-by: mcimadamore

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

@@ -3003,11 +3003,11 @@ public class Check {
                 Set<Name> applicableTargets = applicableTargetsOp.get();
                 boolean notApplicableOrIsTypeUseOnly = applicableTargets.isEmpty() ||
                         applicableTargets.size() == 1 && applicableTargets.contains(names.TYPE_USE);
-                boolean isRecordMemberWithNonApplicableDeclAnno =
-                        isRecordMember && (s.flags_field & Flags.GENERATED_MEMBER) != 0 && notApplicableOrIsTypeUseOnly;
+                boolean isCompGeneratedRecordElement = isRecordMember && (s.flags_field & Flags.GENERATED_MEMBER) != 0;
+                boolean isCompRecordElementWithNonApplicableDeclAnno = isCompGeneratedRecordElement && notApplicableOrIsTypeUseOnly;
 
-                if (applicableTargets.isEmpty() || isRecordMemberWithNonApplicableDeclAnno) {
-                    if (isRecordMemberWithNonApplicableDeclAnno) {
+                if (applicableTargets.isEmpty() || isCompRecordElementWithNonApplicableDeclAnno) {
+                    if (isCompRecordElementWithNonApplicableDeclAnno) {
                             /* so we have found an annotation that is not applicable to a record member that was generated by the
                              * compiler. This was intentionally done at TypeEnter, now is the moment strip away the annotations
                              * that are not applicable to the given record member
@@ -3031,6 +3031,13 @@ public class Check {
                         log.error(a.pos(), Errors.AnnotationTypeNotApplicable);
                     }
                 }
+                /* if we are seeing the @SafeVarargs annotation applied to a compiler generated accessor,
+                 * then this is an error as we know that no compiler generated accessor will be a varargs
+                 * method, better to fail asap
+                 */
+                if (isCompGeneratedRecordElement && !isRecordField && a.type.tsym == syms.trustMeType.tsym && declarationTree.hasTag(METHODDEF)) {
+                    log.error(a.pos(), Errors.VarargsInvalidTrustmeAnno(syms.trustMeType.tsym, Fragments.VarargsTrustmeOnNonVarargsAccessor(s)));
+                }
             }
         }
 

src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties

@@ -1419,6 +1419,10 @@ compiler.err.instanceof.pattern.no.subtype=\
 compiler.misc.varargs.trustme.on.non.varargs.meth=\
     Method {0} is not a varargs method.
 
+# 0: symbol
+compiler.misc.varargs.trustme.on.non.varargs.accessor=\
+    Accessor {0} is not a varargs method.
+
 # 0: symbol
 compiler.misc.varargs.trustme.on.virtual.varargs=\
     Instance method {0} is neither final nor private.

test/langtools/tools/javac/diags/examples/SafeVarargsNotApplicableToRecordAccessors.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2020, 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.
+ */
+
+// key: compiler.err.varargs.invalid.trustme.anno
+// key: compiler.misc.varargs.trustme.on.non.varargs.accessor
+// key: compiler.note.preview.filename
+// key: compiler.note.preview.recompile
+// options: --enable-preview -source ${jdk.version}
+
+record R(@SafeVarargs String... s) {}

test/langtools/tools/javac/records/RecordCompilationTests.java

@@ -1825,4 +1825,21 @@ public class RecordCompilationTests extends CompilationTestCase {
                 """
         );
     }
+
+    public void testSaveVarargsAnno() {
+        // the compiler would generate an erronous accessor
+        assertFail("compiler.err.varargs.invalid.trustme.anno",
+                """
+                record R(@SafeVarargs String... s) {}
+                """
+        );
+        // but this is OK
+        assertOK(
+                """
+                record R(@SafeVarargs String... s) {
+                    public String[] s() { return s; }
+                }
+                """
+        );
+    }
 }