8075793: Source incompatibility for inference using -source 7

Summary: In pre-8 sources, avoid capture variables as inference bounds, consistent with old javac behavior
Reviewed-by: vromero, mcimadamore

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Source.java

@@ -209,6 +209,9 @@ public enum Source {
     public boolean allowPostApplicabilityVarargsAccessCheck() {
         return compareTo(JDK1_8) >= 0;
     }
+    public boolean mapCapturesToBounds() {
+        return compareTo(JDK1_8) < 0;
+    }
     public boolean allowPrivateSafeVarargs() {
         return compareTo(JDK1_9) >= 0;
     }

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Type.java

@@ -2082,6 +2082,21 @@ public abstract class Type extends AnnoConstruct implements TypeMirror {
 
         /** add a bound of a given kind - this might trigger listener notification */
         public final void addBound(InferenceBound ib, Type bound, Types types) {
+            // Per JDK-8075793: in pre-8 sources, follow legacy javac behavior
+            // when capture variables are inferred as bounds: for lower bounds,
+            // map to the capture variable's upper bound; for upper bounds,
+            // if the capture variable has a lower bound, map to that type
+            if (types.mapCapturesToBounds) {
+                switch (ib) {
+                    case LOWER:
+                        bound = types.cvarUpperBound(bound);
+                        break;
+                    case UPPER:
+                        Type altBound = types.cvarLowerBound(bound);
+                        if (!altBound.hasTag(TypeTag.BOT)) bound = altBound;
+                        break;
+                }
+            }
             addBound(ib, bound, types, false);
         }
 

langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java

@@ -88,6 +88,7 @@ public class Types {
     final Names names;
     final boolean allowObjectToPrimitiveCast;
     final boolean allowDefaultMethods;
+    final boolean mapCapturesToBounds;
     final Check chk;
     final Enter enter;
     JCDiagnostic.Factory diags;
@@ -112,6 +113,7 @@ public class Types {
         Source source = Source.instance(context);
         allowObjectToPrimitiveCast = source.allowObjectToPrimitiveCast();
         allowDefaultMethods = source.allowDefaultMethods();
+        mapCapturesToBounds = source.mapCapturesToBounds();
         chk = Check.instance(context);
         enter = Enter.instance(context);
         capturedName = names.fromString("<captured wildcard>");

langtools/test/tools/javac/generics/inference/CaptureLowerBound.java

 /*
- * Copyright (c) 2014, 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
+ * @test /nodynamiccopyright/
  * @bug 8039214
  * @summary Capture variable as an inference variable's lower bound
  * @compile CaptureLowerBound.java
+ * @compile/fail/ref=CaptureLowerBound7.out -Xlint:-options -source 7 -XDrawDiagnostics CaptureLowerBound.java
  */
 
 public class CaptureLowerBound {

langtools/test/tools/javac/generics/inference/CaptureLowerBound7.out

+CaptureLowerBound.java:17:7: compiler.err.cant.apply.symbol: kindname.method, m, CaptureLowerBound.I<? extends X,X>, CaptureLowerBound.C<compiler.misc.type.captureof: 1, ?>, kindname.class, CaptureLowerBound, (compiler.misc.inferred.do.not.conform.to.lower.bounds: compiler.misc.type.captureof: 1, ?, java.lang.Object)
+1 error

langtools/test/tools/javac/generics/inference/CaptureLowerBoundArray.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug 8075793
+ * @summary Capture variable as an inference lower bound followed by an array write
+ * @compile/fail/ref=CaptureLowerBoundArray.out -XDrawDiagnostics CaptureLowerBoundArray.java
+ * @compile -Xlint:-options -source 7 CaptureLowerBoundArray.java
+ */
+
+class CaptureLowerBoundArray {
+
+    interface I<T> {
+        T[] getArray();
+    }
+
+    <T> T[] m(T[] arg) { return null; }
+
+    void test(I<? extends Exception> i) {
+        m(i.getArray())[0] = new Exception();
+    }
+
+
+}

langtools/test/tools/javac/generics/inference/CaptureLowerBoundArray.out

+CaptureLowerBoundArray.java:18:30: compiler.err.prob.found.req: (compiler.misc.inconvertible.types: java.lang.Exception, compiler.misc.type.captureof: 1, ? extends java.lang.Exception)
+1 error

langtools/test/tools/javac/generics/inference/CaptureLowerBoundAssign.java

+/*
+ * Copyright (c) 2016, 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 8075793
+ * @summary Capture variable as an inference lower bound followed by an invariant assignment
+ * @compile CaptureLowerBoundAssign.java
+ * @compile -Xlint:-options -source 7 CaptureLowerBoundAssign.java
+ */
+
+class CaptureLowerBoundAssign {
+
+    static class C<T> {}
+
+    <T> C<T> m(C<? extends T> x) { return null; }
+
+    void test(C<? extends Number> arg) {
+        C<Number> c = m(arg);
+    }
+
+}
\ No newline at end of file

langtools/test/tools/javac/generics/inference/CaptureLowerBoundDeref.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug 8075793
+ * @summary Capture variable as an inference lower bound followed by a member reference
+ * @compile/fail/ref=CaptureLowerBoundDeref.out -XDrawDiagnostics CaptureLowerBoundDeref.java
+ * @compile -Xlint:-options -source 7 CaptureLowerBoundDeref.java
+ */
+
+class CaptureLowerBoundDeref {
+
+    interface Wrapper<T> {
+        I<T> get();
+    }
+
+    interface I<T> {}
+
+    interface K<T> { void take(T arg); }
+
+    <T> K<T> m(I<? extends T> arg) { return null; }
+
+    void test(Wrapper<?> w) {
+        m(w.get()).take(new Object());
+    }
+}
\ No newline at end of file

langtools/test/tools/javac/generics/inference/CaptureLowerBoundDeref.out

+CaptureLowerBoundDeref.java:22:19: compiler.err.cant.apply.symbol: kindname.method, take, compiler.misc.type.captureof: 1, ?, java.lang.Object, kindname.interface, CaptureLowerBoundDeref.K<T>, (compiler.misc.no.conforming.assignment.exists: (compiler.misc.inconvertible.types: java.lang.Object, compiler.misc.type.captureof: 1, ?))
+1 error

langtools/test/tools/javac/generics/inference/CaptureLowerBoundNeg.java

@@ -3,6 +3,7 @@
  * @bug 8039214
  * @summary Capture variable as an inference variable's lower bound
  * @compile/fail/ref=CaptureLowerBoundNeg.out -XDrawDiagnostics CaptureLowerBoundNeg.java
+ * @compile -Xlint:-options -source 7 CaptureLowerBoundNeg.java
  */
 
 public class CaptureLowerBoundNeg {

langtools/test/tools/javac/generics/inference/CaptureLowerBoundNeg.out

-CaptureLowerBoundNeg.java:16:29: compiler.err.cant.apply.symbol: kindname.method, take, compiler.misc.type.captureof: 1, ? extends java.lang.Object, java.lang.Object, kindname.class, CaptureLowerBoundNeg.D<T>, (compiler.misc.no.conforming.assignment.exists: (compiler.misc.inconvertible.types: java.lang.Object, compiler.misc.type.captureof: 1, ? extends java.lang.Object))
+CaptureLowerBoundNeg.java:17:29: compiler.err.cant.apply.symbol: kindname.method, take, compiler.misc.type.captureof: 1, ? extends java.lang.Object, java.lang.Object, kindname.class, CaptureLowerBoundNeg.D<T>, (compiler.misc.no.conforming.assignment.exists: (compiler.misc.inconvertible.types: java.lang.Object, compiler.misc.type.captureof: 1, ? extends java.lang.Object))
 1 error

langtools/test/tools/javac/generics/inference/CaptureUpperBoundDeref.java

+/*
+ * @test /nodynamiccopyright/
+ * @bug 8075793
+ * @summary Capture variable as an inference upper bound followed by a member reference
+ * @compile/fail/ref=CaptureUpperBoundDeref.out -XDrawDiagnostics CaptureUpperBoundDeref.java
+ * @compile -Xlint:-options -source 7 CaptureUpperBoundDeref.java
+ */
+
+class CaptureUpperBoundDeref {
+
+    interface Wrapper<T> {
+        I<T> get();
+    }
+
+    interface I<T> {}
+
+    <T> T m(I<? super T> arg) { return null; }
+
+    void test(Wrapper<? super String> w) {
+        m(w.get()).substring(0);
+    }
+}
\ No newline at end of file

langtools/test/tools/javac/generics/inference/CaptureUpperBoundDeref.out

+CaptureUpperBoundDeref.java:20:19: compiler.err.cant.resolve.location.args: kindname.method, substring, , int, (compiler.misc.location: kindname.class, java.lang.Object, null)
+1 error

langtools/test/tools/javac/generics/inference/NestedCapture.java

@@ -26,6 +26,7 @@
  * @bug 8039214
  * @summary Capture variable passed through multiple levels of nested inference
  * @compile NestedCapture.java
+ * @compile -Xlint:-options -source 7 NestedCapture.java
  */
 
 abstract class NestedCapture {

langtools/test/tools/javac/generics/inference/NestedWildcards.java

@@ -26,6 +26,7 @@
  * @bug 8039214
  * @summary Nested generic methods that work on wildcard-parameterized types
  * @compile NestedWildcards.java
+ * @compile -Xlint:-options -source 7 NestedWildcards.java
  */
 
 public class NestedWildcards {