Constraint Foo on T! should be turned into Foo! on T

compiler/testData/diagnostics/tests/platformTypes/methodCall/singleton.kt

@@ -0,0 +1,8 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
+
+trait Foo
+
+fun test() {
+    var nullable: Foo? = null
+    val foo: Collection<Foo> = java.util.Collections.singleton(nullable)
+}

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -7795,6 +7795,11 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
                 
+                @TestMetadata("singleton.kt")
+                public void testSingleton() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/platformTypes/methodCall/singleton.kt");
+                }
+                
                 @TestMetadata("string.kt")
                 public void testString() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/methodCall/string.kt");