diff --git a/src/share/classes/com/sun/tools/javac/comp/Attr.java b/src/share/classes/com/sun/tools/javac/comp/Attr.java
index cf1cf2c7f053ab5149c11fd968f3bc36236ebeb4..3f776c51038e9803e88eeca6bef56d0e7c6b8440 100644
--- a/src/share/classes/com/sun/tools/javac/comp/Attr.java
+++ b/src/share/classes/com/sun/tools/javac/comp/Attr.java
@@ -1472,7 +1472,7 @@ 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((ClassType)clazztype);
+        Pair<Scope,Scope> mapping = getSyntheticScopeMapping(clazztype);
         if (!TreeInfo.isDiamond(tree)) {
             clazztype = chk.checkClassType(
                 tree.clazz.pos(), clazztype, true);
@@ -1640,9 +1640,10 @@ public class Attr extends JCTree.Visitor {
                         List<Type> argtypes,
                         List<Type> typeargtypes,
                         boolean reportErrors) {
-        if (clazztype.isErroneous()) {
-            //if the type of the instance creation expression is erroneous
-            //return the erroneous type itself
+        if (clazztype.isErroneous() || mapping == erroneousMapping) {
+            //if the type of the instance creation expression is erroneous,
+            //or something prevented us to form a valid mapping, return the
+            //(possibly erroneous) type unchanged
             return clazztype;
         }
         else if (clazztype.isInterface()) {
@@ -1740,7 +1741,10 @@ 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(ClassType ctype) {
+    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();
@@ -1763,6 +1767,8 @@ public class Attr extends JCTree.Visitor {
         return mapping;
     }
 
+    private final Pair<Scope,Scope> erroneousMapping = new Pair<Scope,Scope>(null, null);
+
     /** Make an attributed null check tree.
      */
     public JCExpression makeNullCheck(JCExpression arg) {
diff --git a/test/tools/javac/generics/6946618/T6946618a.java b/test/tools/javac/generics/6946618/T6946618a.java
new file mode 100644
index 0000000000000000000000000000000000000000..7ddabc21d4c587394b0355bea9e34af66ee78393
--- /dev/null
+++ b/test/tools/javac/generics/6946618/T6946618a.java
@@ -0,0 +1,21 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug     6946618
+ * @summary sqe test fails: javac/generics/NewOnTypeParm  in pit jdk7 b91 in all platforms.
+ * @author  mcimadamore
+ * @compile/fail/ref=T6946618a.out -XDrawDiagnostics T6946618a.java
+ */
+
+class T6946618a {
+    static class C<T> {
+      T makeT() {
+        return new T(); //error
+      }
+    }
+
+    static class D<S> {
+      C<S> makeC() {
+        return new C<S>(); //ok
+      }
+    }
+}
diff --git a/test/tools/javac/generics/6946618/T6946618a.out b/test/tools/javac/generics/6946618/T6946618a.out
new file mode 100644
index 0000000000000000000000000000000000000000..dfb46b49f3d667ac54a526cfa1bc78aa0fbeedd9
--- /dev/null
+++ b/test/tools/javac/generics/6946618/T6946618a.out
@@ -0,0 +1,2 @@
+T6946618a.java:12:20: compiler.err.type.found.req: (compiler.misc.type.parameter: T), (compiler.misc.type.req.class)
+1 error
diff --git a/test/tools/javac/generics/6946618/T6946618b.java b/test/tools/javac/generics/6946618/T6946618b.java
new file mode 100644
index 0000000000000000000000000000000000000000..af600a92c4148b4d5e9ad60139710eeeef330d5f
--- /dev/null
+++ b/test/tools/javac/generics/6946618/T6946618b.java
@@ -0,0 +1,21 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug     6946618
+ * @summary sqe test fails: javac/generics/NewOnTypeParm  in pit jdk7 b91 in all platforms.
+ * @author  mcimadamore
+ * @compile/fail/ref=T6946618b.out -XDrawDiagnostics T6946618b.java
+ */
+
+class T6946618b {
+    static class C<T> {
+      T makeT() {
+        return new T<>(); //error
+      }
+    }
+
+    static class D<S> {
+      C<S> makeC() {
+        return new C<>(); //ok
+      }
+    }
+}
diff --git a/test/tools/javac/generics/6946618/T6946618b.out b/test/tools/javac/generics/6946618/T6946618b.out
new file mode 100644
index 0000000000000000000000000000000000000000..d5460848be55a8ce65adcdcc2678c26020c3c9b3
--- /dev/null
+++ b/test/tools/javac/generics/6946618/T6946618b.out
@@ -0,0 +1,2 @@
+T6946618b.java:12:20: compiler.err.type.found.req: (compiler.misc.type.parameter: T), (compiler.misc.type.req.class)
+1 error
diff --git a/test/tools/javac/generics/6946618/T6946618c.java b/test/tools/javac/generics/6946618/T6946618c.java
new file mode 100644
index 0000000000000000000000000000000000000000..034ecb5e4fb5e9f047cec3c18bf46f768610668e
--- /dev/null
+++ b/test/tools/javac/generics/6946618/T6946618c.java
@@ -0,0 +1,17 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug     6946618
+ * @summary sqe test fails: javac/generics/NewOnTypeParm  in pit jdk7 b91 in all platforms.
+ * @author  mcimadamore
+ * @compile/fail/ref=T6946618c.out -XDrawDiagnostics T6946618c.java
+ */
+
+class T6946618c {
+    static class C<T> { }
+
+    void test() {
+        C<?> c1 = new C<? extends String>();
+        C<?> c2 = new C<? super String>();
+        C<?> c3 = new C<?>();
+    }
+}
diff --git a/test/tools/javac/generics/6946618/T6946618c.out b/test/tools/javac/generics/6946618/T6946618c.out
new file mode 100644
index 0000000000000000000000000000000000000000..01da79b2cc9fe20a93ea7aa32207298ec8efe5c2
--- /dev/null
+++ b/test/tools/javac/generics/6946618/T6946618c.out
@@ -0,0 +1,4 @@
+T6946618c.java:13:24: compiler.err.type.found.req: ? extends java.lang.String, class or interface without bounds
+T6946618c.java:14:24: compiler.err.type.found.req: ? super java.lang.String, class or interface without bounds
+T6946618c.java:15:24: compiler.err.type.found.req: ?, class or interface without bounds
+3 errors