7030150: Type inference for generic instance creation failed for formal type parameter

Problem when explicit generic constructor type-arguments are used in conjunction with diamond

Reviewed-by: jjg

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

@@ -2461,6 +2461,22 @@ public class Types {
             }
         };
 
+    public Type createMethodTypeWithReturn(Type original, Type newReturn) {
+        return original.accept(methodWithReturn, newReturn);
+    }
+    // where
+        private final MapVisitor<Type> methodWithReturn = new MapVisitor<Type>() {
+            public Type visitType(Type t, Type newReturn) {
+                throw new IllegalArgumentException("Not a method type: " + t);
+            }
+            public Type visitMethodType(MethodType t, Type newReturn) {
+                return new MethodType(t.argtypes, newReturn, t.thrown, t.tsym);
+            }
+            public Type visitForAll(ForAll t, Type newReturn) {
+                return new ForAll(t.tvars, t.qtype.accept(this, newReturn));
+            }
+        };
+
     // <editor-fold defaultstate="collapsed" desc="createErrorType">
     public Type createErrorType(Type originalType) {
         return new ErrorType(originalType, syms.errSymbol);

langtools/src/share/classes/com/sun/tools/javac/comp/Attr.java

@@ -1580,7 +1580,7 @@ public class Attr extends JCTree.Visitor {
         // Attribute clazz expression and store
         // symbol + type back into the attributed tree.
         Type clazztype = attribType(clazz, env);
-        Pair<Scope,Scope> mapping = getSyntheticScopeMapping(clazztype, cdef != null);
+        Pair<Scope,Scope> mapping = getSyntheticScopeMapping(clazztype);
         clazztype = chk.checkDiamond(tree, clazztype);
         chk.validate(clazz, localEnv);
         if (tree.encl != null) {
@@ -1778,62 +1778,48 @@ public class Attr extends JCTree.Visitor {
                         Pair<Scope, Scope> mapping,
                         List<Type> argtypes,
                         List<Type> typeargtypes) {
-        if (clazztype.isErroneous() || mapping == erroneousMapping) {
+        if (clazztype.isErroneous() ||
+                clazztype.isInterface() ||
+                mapping == erroneousMapping) {
             //if the type of the instance creation expression is erroneous,
-            //or something prevented us to form a valid mapping, return the
+            //or if it's an interface, or if something prevented us to form a valid
-            //(possibly erroneous) type unchanged
+            //mapping, return the (possibly erroneous) type unchanged
             return clazztype;
         }
-        else if (clazztype.isInterface()) {
+
-            //if the type of the instance creation expression is an interface
+        //dup attribution environment and augment the set of inference variables
-            //skip the method resolution step (JLS 15.12.2.7). The type to be
+        Env<AttrContext> localEnv = env.dup(tree);
-            //inferred is of the kind <X1,X2, ... Xn>C<X1,X2, ... Xn>
+        localEnv.info.tvars = clazztype.tsym.type.getTypeArguments();
-            clazztype = new ForAll(clazztype.tsym.type.allparams(), clazztype.tsym.type) {
+
-                @Override
+        //if the type of the instance creation expression is a class type
-                public List<Type> getConstraints(TypeVar tv, ConstraintKind ck) {
+        //apply method resolution inference (JLS 15.12.2.7). The return type
-                    switch (ck) {
+        //of the resolved constructor will be a partially instantiated type
-                        case EXTENDS: return types.getBounds(tv);
+        ((ClassSymbol) clazztype.tsym).members_field = mapping.snd;
-                        default: return List.nil();
+        Symbol constructor;
-                    }
+        try {
-                }
+            constructor = rs.resolveDiamond(tree.pos(),
-                @Override
+                    localEnv,
-                public Type inst(List<Type> inferred, Types types) throws Infer.NoInstanceException {
+                    clazztype.tsym.type,
-                    // check that inferred bounds conform to their bounds
+                    argtypes,
-                    infer.checkWithinBounds(tvars,
+                    typeargtypes);
-                           types.subst(tvars, tvars, inferred), Warner.noWarnings);
+        } finally {
-                    return super.inst(inferred, types);
+            ((ClassSymbol) clazztype.tsym).members_field = mapping.fst;
-                }
-            };
-        } else {
-            //if the type of the instance creation expression is a class type
-            //apply method resolution inference (JLS 15.12.2.7). The return type
-            //of the resolved constructor will be a partially instantiated type
-            ((ClassSymbol) clazztype.tsym).members_field = mapping.snd;
-            Symbol constructor;
-            try {
-                constructor = rs.resolveDiamond(tree.pos(),
-                        env,
-                        clazztype.tsym.type,
-                        argtypes,
-                        typeargtypes);
-            } finally {
-                ((ClassSymbol) clazztype.tsym).members_field = mapping.fst;
-            }
-            if (constructor.kind == MTH) {
-                ClassType ct = new ClassType(clazztype.getEnclosingType(),
-                        clazztype.tsym.type.getTypeArguments(),
-                        clazztype.tsym);
-                clazztype = checkMethod(ct,
-                        constructor,
-                        env,
-                        tree.args,
-                        argtypes,
-                        typeargtypes,
-                        env.info.varArgs).getReturnType();
-            } else {
-                clazztype = syms.errType;
-            }
         }
+        if (constructor.kind == MTH) {
+            ClassType ct = new ClassType(clazztype.getEnclosingType(),
+                    clazztype.tsym.type.getTypeArguments(),
+                    clazztype.tsym);
+            clazztype = checkMethod(ct,
+                    constructor,
+                    localEnv,
+                    tree.args,
+                    argtypes,
+                    typeargtypes,
+                    localEnv.info.varArgs).getReturnType();
+        } else {
+            clazztype = syms.errType;
+        }
+
         if (clazztype.tag == FORALL && !pt.isErroneous()) {
             //if the resolved constructor's return type has some uninferred
             //type-variables, infer them using the expected type and declared
@@ -1863,34 +1849,28 @@ public class Attr extends JCTree.Visitor {
      *  inference. The inferred return type of the synthetic constructor IS
      *  the inferred type for the diamond operator.
      */
-    private Pair<Scope, Scope> getSyntheticScopeMapping(Type ctype, boolean overrideProtectedAccess) {
+    private Pair<Scope, Scope> getSyntheticScopeMapping(Type ctype) {
         if (ctype.tag != CLASS) {
             return erroneousMapping;
         }
+
         Pair<Scope, Scope> mapping =
                 new Pair<Scope, Scope>(ctype.tsym.members(), new Scope(ctype.tsym));
-        List<Type> typevars = ctype.tsym.type.getTypeArguments();
+
+        //for each constructor in the original scope, create a synthetic constructor
+        //whose return type is the type of the class in which the constructor is
+        //declared, and insert it into the new scope.
         for (Scope.Entry e = mapping.fst.lookup(names.init);
                 e.scope != null;
                 e = e.next()) {
-            MethodSymbol newConstr = (MethodSymbol) e.sym.clone(ctype.tsym);
+            Type synthRestype = new ClassType(ctype.getEnclosingType(),
-            if (overrideProtectedAccess && (newConstr.flags() & PROTECTED) != 0) {
+                        ctype.tsym.type.getTypeArguments(),
-                //make protected constructor public (this is required for
+                        ctype.tsym);
-                //anonymous inner class creation expressions using diamond)
+            MethodSymbol synhConstr = new MethodSymbol(e.sym.flags(),
-                newConstr.flags_field |= PUBLIC;
+                    names.init,
-                newConstr.flags_field &= ~PROTECTED;
+                    types.createMethodTypeWithReturn(e.sym.type, synthRestype),
-            }
+                    e.sym.owner);
-            newConstr.name = names.init;
+            mapping.snd.enter(synhConstr);
-            List<Type> oldTypeargs = List.nil();
-            if (newConstr.type.tag == FORALL) {
-                oldTypeargs = ((ForAll) newConstr.type).tvars;
-            }
-            newConstr.type = new MethodType(newConstr.type.getParameterTypes(),
-                    new ClassType(ctype.getEnclosingType(), ctype.tsym.type.getTypeArguments(), ctype.tsym),
-                    newConstr.type.getThrownTypes(),
-                    syms.methodClass);
-            newConstr.type = new ForAll(typevars.prependList(oldTypeargs), newConstr.type);
-            mapping.snd.enter(newConstr);
         }
         return mapping;
     }

langtools/src/share/classes/com/sun/tools/javac/comp/Resolve.java

@@ -338,7 +338,11 @@ public class Resolve {
 
         // tvars is the list of formal type variables for which type arguments
         // need to inferred.
-        List<Type> tvars = env.info.tvars;
+        List<Type> tvars = null;
+        if (env.info.tvars != null) {
+            tvars = types.newInstances(env.info.tvars);
+            mt = types.subst(mt, env.info.tvars, tvars);
+        }
         if (typeargtypes == null) typeargtypes = List.nil();
         if (mt.tag != FORALL && typeargtypes.nonEmpty()) {
             // This is not a polymorphic method, but typeargs are supplied

langtools/test/tools/javac/generics/diamond/7030150/GenericConstructorAndDiamondTest.java

@@ -0,0 +1,252 @@
+/*
+ * Copyright (c) 2011, 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 7030150
+ * @summary Type inference for generic instance creation failed for formal type parameter
+ */
+
+import com.sun.source.util.JavacTask;
+import java.net.URI;
+import java.util.Arrays;
+import javax.tools.Diagnostic;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.ToolProvider;
+
+public class GenericConstructorAndDiamondTest {
+
+    enum BoundKind {
+        NO_BOUND(""),
+        STRING_BOUND("extends String"),
+        INTEGER_BOUND("extends Integer");
+
+        String boundStr;
+
+        private BoundKind(String boundStr) {
+            this.boundStr = boundStr;
+        }
+
+        boolean matches(TypeArgumentKind tak) {
+            switch (tak) {
+                case NONE: return true;
+                case STRING: return this != INTEGER_BOUND;
+                case INTEGER: return this != STRING_BOUND;
+                default: return false;
+            }
+        }
+    }
+
+    enum ConstructorKind {
+        NON_GENERIC("Foo(Object o) {}"),
+        GENERIC_NO_BOUND("<T> Foo(T t) {}"),
+        GENERIC_STRING_BOUND("<T extends String> Foo(T t) {}"),
+        GENERIC_INTEGER_BOUND("<T extends Integer> Foo(T t) {}");
+
+        String constrStr;
+
+        private ConstructorKind(String constrStr) {
+            this.constrStr = constrStr;
+        }
+
+        boolean matches(ArgumentKind ak) {
+            switch (ak) {
+                case STRING: return this != GENERIC_INTEGER_BOUND;
+                case INTEGER: return this != GENERIC_STRING_BOUND;
+                default: return false;
+            }
+        }
+    }
+
+    enum TypeArgArity {
+        ONE(1),
+        TWO(2),
+        THREE(3);
+
+        int n;
+
+        private TypeArgArity(int n) {
+            this.n = n;
+        }
+    }
+
+    enum TypeArgumentKind {
+        NONE(""),
+        STRING("String"),
+        INTEGER("Integer");
+
+        String typeargStr;
+
+        private TypeArgumentKind(String typeargStr) {
+            this.typeargStr = typeargStr;
+        }
+
+        String getArgs(TypeArgArity arity) {
+            if (this == NONE) return "";
+            else {
+                StringBuilder buf = new StringBuilder();
+                String sep = "";
+                for (int i = 0 ; i < arity.n ; i++) {
+                    buf.append(sep);
+                    buf.append(typeargStr);
+                    sep = ",";
+                }
+                return "<" + buf.toString() + ">";
+            }
+        }
+
+        boolean matches(ArgumentKind ak) {
+            switch (ak) {
+                case STRING: return this != INTEGER;
+                case INTEGER: return this != STRING;
+                default: return false;
+            }
+        }
+    }
+
+    enum ArgumentKind {
+        STRING("\"\""),
+        INTEGER("1");
+
+        String argStr;
+
+        private ArgumentKind(String argStr) {
+            this.argStr = argStr;
+        }
+    }
+
+    public static void main(String... args) throws Exception {
+
+        //create default shared JavaCompiler - reused across multiple compilations
+        JavaCompiler comp = ToolProvider.getSystemJavaCompiler();
+        StandardJavaFileManager fm = comp.getStandardFileManager(null, null, null);
+
+        for (BoundKind boundKind : BoundKind.values()) {
+            for (ConstructorKind constructorKind : ConstructorKind.values()) {
+                for (TypeArgumentKind declArgKind : TypeArgumentKind.values()) {
+                    for (TypeArgArity arity : TypeArgArity.values()) {
+                        for (TypeArgumentKind useArgKind : TypeArgumentKind.values()) {
+                            for (ArgumentKind argKind : ArgumentKind.values()) {
+                                new GenericConstructorAndDiamondTest(boundKind, constructorKind,
+                                        declArgKind, arity, useArgKind, argKind).run(comp, fm);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    BoundKind boundKind;
+    ConstructorKind constructorKind;
+    TypeArgumentKind declTypeArgumentKind;
+    TypeArgArity useTypeArgArity;
+    TypeArgumentKind useTypeArgumentKind;
+    ArgumentKind argumentKind;
+    JavaSource source;
+    DiagnosticChecker diagChecker;
+
+    GenericConstructorAndDiamondTest(BoundKind boundKind, ConstructorKind constructorKind,
+            TypeArgumentKind declTypeArgumentKind, TypeArgArity useTypeArgArity,
+            TypeArgumentKind useTypeArgumentKind, ArgumentKind argumentKind) {
+        this.boundKind = boundKind;
+        this.constructorKind = constructorKind;
+        this.declTypeArgumentKind = declTypeArgumentKind;
+        this.useTypeArgArity = useTypeArgArity;
+        this.useTypeArgumentKind = useTypeArgumentKind;
+        this.argumentKind = argumentKind;
+        this.source = new JavaSource();
+        this.diagChecker = new DiagnosticChecker();
+    }
+
+    class JavaSource extends SimpleJavaFileObject {
+
+        String template = "class Foo<X #BK> {\n" +
+                              "#CK\n" +
+                          "}\n" +
+                          "class Test {\n" +
+                              "void test() {\n" +
+                                 "Foo#TA1 f = new #TA2 Foo<>(#A);\n" +
+                              "}\n" +
+                          "}\n";
+
+        String source;
+
+        public JavaSource() {
+            super(URI.create("myfo:/Test.java"), JavaFileObject.Kind.SOURCE);
+            source = template.replace("#BK", boundKind.boundStr).
+                    replace("#CK", constructorKind.constrStr)
+                    .replace("#TA1", declTypeArgumentKind.getArgs(TypeArgArity.ONE))
+                    .replace("#TA2", useTypeArgumentKind.getArgs(useTypeArgArity))
+                    .replace("#A", argumentKind.argStr);
+        }
+
+        @Override
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+            return source;
+        }
+    }
+
+    void run(JavaCompiler tool, StandardJavaFileManager fm) throws Exception {
+        JavacTask ct = (JavacTask)tool.getTask(null, fm, diagChecker,
+                null, null, Arrays.asList(source));
+        ct.analyze();
+        check();
+    }
+
+    void check() {
+        boolean badActual = !constructorKind.matches(argumentKind);
+
+        boolean badArity = constructorKind != ConstructorKind.NON_GENERIC &&
+                useTypeArgumentKind != TypeArgumentKind.NONE &&
+                useTypeArgArity != TypeArgArity.ONE;
+
+        boolean badMethodTypeArg = constructorKind != ConstructorKind.NON_GENERIC &&
+                !useTypeArgumentKind.matches(argumentKind);
+
+        boolean badGenericType = !boundKind.matches(declTypeArgumentKind);
+
+        boolean shouldFail = badActual || badArity || badMethodTypeArg || badGenericType;
+
+        if (shouldFail != diagChecker.errorFound) {
+            throw new Error("invalid diagnostics for source:\n" +
+                source.getCharContent(true) +
+                "\nFound error: " + diagChecker.errorFound +
+                "\nExpected error: " + shouldFail);
+        }
+    }
+
+    static class DiagnosticChecker implements javax.tools.DiagnosticListener<JavaFileObject> {
+
+        boolean errorFound;
+
+        public void report(Diagnostic<? extends JavaFileObject> diagnostic) {
+            if (diagnostic.getKind() == Diagnostic.Kind.ERROR) {
+                errorFound = true;
+            }
+        }
+    }
+}

langtools/test/tools/javac/generics/diamond/7030150/Neg01.java

@@ -0,0 +1,17 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 7030150
+ * @summary Type inference for generic instance creation failed for formal type parameter
+ *          check that explicit type-argument that causes resolution failure is rejected
+ * @compile/fail/ref=Neg01.out -XDrawDiagnostics Neg01.java
+ */
+
+class Neg01 {
+
+    static class Foo<X> {
+        <T> Foo(T t) {}
+    }
+
+    Foo<Integer> fi1 = new <String> Foo<>(1);
+    Foo<Integer> fi2 = new <String> Foo<Integer>(1);
+}

langtools/test/tools/javac/generics/diamond/7030150/Neg01.out

@@ -0,0 +1,3 @@
+Neg01.java:15:24: compiler.err.cant.apply.diamond.1: (compiler.misc.diamond: Neg01.Foo), (compiler.misc.infer.no.conforming.assignment.exists: X, int, java.lang.String)
+Neg01.java:16:24: compiler.err.cant.apply.symbol.1: kindname.constructor, Foo, T, int, kindname.class, Neg01.Foo<X>, (compiler.misc.no.conforming.assignment.exists: int, java.lang.String)
+2 errors

langtools/test/tools/javac/generics/diamond/7030150/Neg02.java

@@ -0,0 +1,17 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 7030150
+ * @summary Type inference for generic instance creation failed for formal type parameter
+ *          check that compiler rejects bad number of explicit type-arguments
+ * @compile/fail/ref=Neg02.out -XDrawDiagnostics Neg02.java
+ */
+
+class Neg02 {
+
+    static class Foo<X> {
+        <T> Foo(T t) {}
+    }
+
+    Foo<Integer> fi1 = new <String, Integer> Foo<>("");
+    Foo<Integer> fi2 = new <String, Integer> Foo<Integer>("");
+}

langtools/test/tools/javac/generics/diamond/7030150/Neg02.out

@@ -0,0 +1,3 @@
+Neg02.java:15:24: compiler.err.cant.apply.diamond.1: (compiler.misc.diamond: Neg02.Foo), (compiler.misc.arg.length.mismatch)
+Neg02.java:16:24: compiler.err.cant.apply.symbol.1: kindname.constructor, Foo, T, java.lang.String, kindname.class, Neg02.Foo<X>, (compiler.misc.arg.length.mismatch)
+2 errors

langtools/test/tools/javac/generics/diamond/7030150/Neg03.java

@@ -0,0 +1,17 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 7030150
+ * @summary Type inference for generic instance creation failed for formal type parameter
+ *          check that explicit type-argument that does not conform to bound is rejected
+ * @compile/fail/ref=Neg03.out -XDrawDiagnostics Neg03.java
+ */
+
+class Neg03 {
+
+    static class Foo<X> {
+        <T extends Integer> Foo(T t) {}
+    }
+
+    Foo<Integer> fi1 = new <String> Foo<>(1);
+    Foo<Integer> fi2 = new <String> Foo<Integer>(1);
+}

langtools/test/tools/javac/generics/diamond/7030150/Neg03.out

@@ -0,0 +1,3 @@
+Neg03.java:15:24: compiler.err.cant.apply.diamond.1: (compiler.misc.diamond: Neg03.Foo), (compiler.misc.explicit.param.do.not.conform.to.bounds: java.lang.String, java.lang.Integer)
+Neg03.java:16:24: compiler.err.cant.apply.symbol.1: kindname.constructor, Foo, T, int, kindname.class, Neg03.Foo<X>, (compiler.misc.explicit.param.do.not.conform.to.bounds: java.lang.String, java.lang.Integer)
+2 errors

langtools/test/tools/javac/generics/diamond/7030150/Pos01.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2011, 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 7030150
+ * @summary Type inference for generic instance creation failed for formal type parameter
+ *          check that redundant type-arguments on non-generic constructor are accepted
+ * @compile Pos01.java
+ */
+
+class Pos01 {
+
+    static class Foo<X> {
+        Foo(X t) {}
+    }
+
+    Foo<Integer> fi1 = new Foo<>(1);
+    Foo<Integer> fi2 = new Foo<Integer>(1);
+    Foo<Integer> fi3 = new <String> Foo<>(1);
+    Foo<Integer> fi4 = new <String> Foo<Integer>(1);
+    Foo<Integer> fi5 = new <String, String> Foo<>(1);
+    Foo<Integer> fi6 = new <String, String> Foo<Integer>(1);
+}

langtools/test/tools/javac/generics/diamond/7030150/Pos02.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2011, 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 7030150
+ * @summary Type inference for generic instance creation failed for formal type parameter
+ *          check that diamond in return context works w/o problems
+ * @compile Pos02.java
+ */
+
+class Pos02<X> {
+
+    Pos02(X x) {}
+
+
+    Pos02<X> test(X x) {
+        return new Pos02<>(x);
+    }
+}