--- a/src/share/classes/com/sun/tools/javac/comp/Infer.java	Thu Oct 27 15:47:35 2011 -0700
+++ b/src/share/classes/com/sun/tools/javac/comp/Infer.java	Fri Nov 04 19:54:16 2011 +0400
@@ -276,21 +276,18 @@
             // VGJ: sort of inlined maximizeInst() below.  Adding
             // bounds can cause lobounds that are above hibounds.
             List<Type> hibounds = Type.filter(that.hibounds, errorFilter);
+            Type hb = null;
             if (hibounds.isEmpty())
-                return;
-            Type hb = null;
-            if (hibounds.tail.isEmpty())
+                hb = syms.objectType;
+            else if (hibounds.tail.isEmpty())
                 hb = hibounds.head;
-            else for (List<Type> bs = hibounds;
-                      bs.nonEmpty() && hb == null;
-                      bs = bs.tail) {
-                if (isSubClass(bs.head, hibounds))
-                    hb = types.fromUnknownFun.apply(bs.head);
-            }
+            else
+                hb = types.glb(hibounds);
             if (hb == null ||
-                !types.isSubtypeUnchecked(hb, hibounds, warn) ||
-                !types.isSubtypeUnchecked(that.inst, hb, warn))
-                throw ambiguousNoInstanceException;
+                hb.isErroneous())
+                throw ambiguousNoInstanceException
+                        .setMessage("incompatible.upper.bounds",
+                                    that.qtype, hibounds);
         }
     }
 

--- a/src/share/classes/com/sun/tools/javac/resources/compiler.properties	Thu Oct 27 15:47:35 2011 -0700
+++ b/src/share/classes/com/sun/tools/javac/resources/compiler.properties	Fri Nov 04 19:54:16 2011 +0400
@@ -1602,6 +1602,10 @@
 compiler.misc.no.unique.minimal.instance.exists=\
     no unique minimal instance exists for type variable {0} with lower bounds {1}
 
+# 0: type, 1: list of type
+compiler.misc.incompatible.upper.bounds=\
+    inference variable {0} has incompatible upper bounds {1}
+
 # 0: list of type, 1: type, 2: type
 compiler.misc.infer.no.conforming.instance.exists=\
     no instance(s) of type variable(s) {0} exist so that {1} conforms to {2}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javac/diags/examples/IncompatibleUpperBounds.java	Fri Nov 04 19:54:16 2011 +0400
@@ -0,0 +1,38 @@
+/*
+ * 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.
+ */
+
+//key: compiler.err.cant.apply.symbols
+//key: compiler.misc.inapplicable.method
+//key: compiler.misc.arg.length.mismatch
+//key: compiler.misc.incompatible.upper.bounds
+
+import java.util.List;
+
+class IncompatibleUpperBounds {
+    <S> void m(List<? super S> s1, List<? super S> s2) { }
+    void m(Object o) {}
+
+    void test(List<Integer> li, List<String> ls) {
+        m(li, ls);
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javac/generics/inference/7086601/T7086601a.java	Fri Nov 04 19:54:16 2011 +0400
@@ -0,0 +1,34 @@
+/**
+ * @test /nodynamiccopyright/
+ * @bug 7086601
+ * @summary Error message bug: cause for method mismatch is 'null'
+ * @compile/fail/ref=T7086601a.out -XDrawDiagnostics T7086601a.java
+ */
+
+class T7086601 {
+    static <S> void m1(Iterable<? super S> s1, Iterable<? super S> s2) { }
+    static void m1(Object o) {}
+
+    static <S> void m2(Iterable<? super S> s1, Iterable<? super S> s2, Iterable<? super S> s3) { }
+    static void m2(Object o) {}
+
+    @SafeVarargs
+    static <S> void m3(Iterable<? super S>... ss) { }
+    static void m3(Object o) {}
+
+    static void test1(Iterable<String> is, Iterable<Integer> ii) {
+        m1(is, ii);
+    }
+
+    static void test2(Iterable<String> is, Iterable<Integer> ii, Iterable<Double> id) {
+        m2(is, ii, id);
+    }
+
+    static void test3(Iterable<String> is, Iterable<Integer> ii) {
+        m3(is, ii);
+    }
+
+    static void test4(Iterable<String> is, Iterable<Integer> ii, Iterable<Double> id) {
+        m3(is, ii, id);
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javac/generics/inference/7086601/T7086601a.out	Fri Nov 04 19:54:16 2011 +0400
@@ -0,0 +1,5 @@
+T7086601a.java:20:9: compiler.err.cant.apply.symbols: kindname.method, m1, java.lang.Iterable<java.lang.String>,java.lang.Iterable<java.lang.Integer>,{(compiler.misc.inapplicable.method: kindname.method, T7086601, m1(java.lang.Object), (compiler.misc.arg.length.mismatch)),(compiler.misc.inapplicable.method: kindname.method, T7086601, <S>m1(java.lang.Iterable<? super S>,java.lang.Iterable<? super S>), (compiler.misc.incompatible.upper.bounds: S, java.lang.Integer,java.lang.String))}
+T7086601a.java:24:9: compiler.err.cant.apply.symbols: kindname.method, m2, java.lang.Iterable<java.lang.String>,java.lang.Iterable<java.lang.Integer>,java.lang.Iterable<java.lang.Double>,{(compiler.misc.inapplicable.method: kindname.method, T7086601, m2(java.lang.Object), (compiler.misc.arg.length.mismatch)),(compiler.misc.inapplicable.method: kindname.method, T7086601, <S>m2(java.lang.Iterable<? super S>,java.lang.Iterable<? super S>,java.lang.Iterable<? super S>), (compiler.misc.incompatible.upper.bounds: S, java.lang.Double,java.lang.Integer,java.lang.String))}
+T7086601a.java:28:9: compiler.err.cant.apply.symbols: kindname.method, m3, java.lang.Iterable<java.lang.String>,java.lang.Iterable<java.lang.Integer>,{(compiler.misc.inapplicable.method: kindname.method, T7086601, m3(java.lang.Object), (compiler.misc.arg.length.mismatch)),(compiler.misc.inapplicable.method: kindname.method, T7086601, <S>m3(java.lang.Iterable<? super S>...), (compiler.misc.incompatible.upper.bounds: S, java.lang.Integer,java.lang.String))}
+T7086601a.java:32:9: compiler.err.cant.apply.symbols: kindname.method, m3, java.lang.Iterable<java.lang.String>,java.lang.Iterable<java.lang.Integer>,java.lang.Iterable<java.lang.Double>,{(compiler.misc.inapplicable.method: kindname.method, T7086601, m3(java.lang.Object), (compiler.misc.arg.length.mismatch)),(compiler.misc.inapplicable.method: kindname.method, T7086601, <S>m3(java.lang.Iterable<? super S>...), (compiler.misc.incompatible.upper.bounds: S, java.lang.Double,java.lang.Integer,java.lang.String))}
+4 errors

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javac/generics/inference/7086601/T7086601b.java	Fri Nov 04 19:54:16 2011 +0400
@@ -0,0 +1,199 @@
+/*
+ * 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 7086601
+ * @summary Error message bug: cause for method mismatch is 'null'
+ */
+
+import com.sun.source.util.JavacTask;
+import java.net.URI;
+import java.util.Arrays;
+import java.util.ArrayList;
+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 T7086601b {
+
+    static int checkCount = 0;
+
+    enum TypeKind {
+        STRING("String", false),
+        INTEGER("Integer", false),
+        NUMBER("Number", false),
+        SERIALIZABLE("java.io.Serializable", true),
+        CLONEABLE("Cloneable", true),
+        X("X", false),
+        Y("Y", false),
+        Z("Z", false);
+
+        String typeStr;
+        boolean isInterface;
+
+        private TypeKind(String typeStr, boolean isInterface) {
+            this.typeStr = typeStr;
+            this.isInterface = isInterface;
+        }
+
+        boolean isSubtypeof(TypeKind other) {
+            return (this == INTEGER && other == NUMBER ||
+                    this == Z && other == Y ||
+                    this == other);
+        }
+    }
+
+    enum MethodCallKind {
+        ARITY_ONE("m(a1);", 1),
+        ARITY_TWO("m(a1, a2);", 2),
+        ARITY_THREE("m(a1, a2, a3);", 3);
+
+        String invokeString;
+        int arity;
+
+        private MethodCallKind(String invokeString, int arity) {
+            this.invokeString = invokeString;
+            this.arity = arity;
+        }
+    }
+
+    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 (TypeKind a1 : TypeKind.values()) {
+            for (TypeKind a2 : TypeKind.values()) {
+                for (TypeKind a3 : TypeKind.values()) {
+                    for (MethodCallKind mck : MethodCallKind.values()) {
+                        new T7086601b(a1, a2, a3, mck).run(comp, fm);
+                    }
+                }
+            }
+        }
+        System.out.println("Total check executed: " + checkCount);
+    }
+
+    TypeKind a1;
+    TypeKind a2;
+    TypeKind a3;
+    MethodCallKind mck;
+    JavaSource source;
+    DiagnosticChecker diagChecker;
+
+    T7086601b(TypeKind a1, TypeKind a2, TypeKind a3, MethodCallKind mck) {
+        this.a1 = a1;
+        this.a2 = a2;
+        this.a3 = a3;
+        this.mck = mck;
+        this.source = new JavaSource();
+        this.diagChecker = new DiagnosticChecker();
+    }
+
+    class JavaSource extends SimpleJavaFileObject {
+
+        final String bodyTemplate = "import java.util.List;\n"+
+                              "class Test {\n" +
+                              "   <Z> void m(List<? super Z> l1) { }\n" +
+                              "   <Z> void m(List<? super Z> l1, List<? super Z> l2) { }\n" +
+                              "   <Z> void m(List<? super Z> l1, List<? super Z> l2, List<? super Z> l3) { }\n" +
+                              "   <X,Y,Z extends Y> void test(List<#A1> a1, List<#A2> a2, List<#A3> a3) { #MC } }";
+
+        String source;
+
+        public JavaSource() {
+            super(URI.create("myfo:/Test.java"), JavaFileObject.Kind.SOURCE);
+            source = bodyTemplate.replace("#A1", a1.typeStr)
+                             .replace("#A2", a2.typeStr).replace("#A3", a3.typeStr)
+                             .replace("#MC", mck.invokeString);
+        }
+
+        @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));
+        try {
+            ct.analyze();
+        } catch (Throwable ex) {
+            throw new AssertionError("Error thron when compiling the following code:\n" + source.getCharContent(true));
+        }
+        check();
+    }
+
+    void check() {
+        checkCount++;
+
+        boolean errorExpected = false;
+
+        if (mck.arity > 1) {
+            TypeKind[] argtypes = { a1, a2, a3 };
+            ArrayList<TypeKind> classes = new ArrayList<>();
+            for (int i = 0 ; i < mck.arity ; i ++ ) {
+                if (!argtypes[i].isInterface) {
+                    classes.add(argtypes[i]);
+                }
+            }
+            boolean glb_exists = true;
+            for (TypeKind arg_i : classes) {
+                glb_exists = true;
+                for (TypeKind arg_j : classes) {
+                    if (!arg_i.isSubtypeof(arg_j)) {
+                        glb_exists = false;
+                        break;
+                    }
+                }
+                if (glb_exists) break;
+            }
+            errorExpected = !glb_exists;
+        }
+
+        if (errorExpected != diagChecker.errorFound) {
+            throw new Error("invalid diagnostics for source:\n" +
+                source.getCharContent(true) +
+                "\nFound error: " + diagChecker.errorFound +
+                "\nExpected error: " + errorExpected);
+        }
+    }
+
+    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;
+            }
+        }
+    }
+}