KT-2729 Warn on 'T?' where 'T' has a nullable upper bound

compiler/testData/diagnostics/tests/inference/NoInferenceFromDeclaredBounds.kt

@@ -1,4 +1,4 @@
-fun fooT22<T>() : T? {
+fun fooT22<T: Any>() : T? {
   return null
 }
 

compiler/testData/diagnostics/tests/inference/completeInferenceIfManyFailed.kt

@@ -1,10 +1,10 @@
 package d
 
-fun <T> joinT(<!UNUSED_PARAMETER!>x<!>: Int, vararg <!UNUSED_PARAMETER!>a<!>: T): T? {
+fun <T: Any> joinT(<!UNUSED_PARAMETER!>x<!>: Int, vararg <!UNUSED_PARAMETER!>a<!>: T): T? {
     return null
 }
 
-fun <T> joinT(<!UNUSED_PARAMETER!>x<!>: Any, <!UNUSED_PARAMETER!>y<!>: T): T? {
+fun <T: Any> joinT(<!UNUSED_PARAMETER!>x<!>: Any, <!UNUSED_PARAMETER!>y<!>: T): T? {
     return null
 }
 

compiler/testData/diagnostics/tests/inference/regressions/kt2286.kt

@@ -24,4 +24,4 @@ abstract class Buggy {
 }
 
 //from library
-fun <T> Iterable<T>.find(<!UNUSED_PARAMETER!>predicate<!>: (T) -> Boolean) : T? {<!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>
+fun <T: Any> Iterable<T>.find(<!UNUSED_PARAMETER!>predicate<!>: (T) -> Boolean) : T? {<!NO_RETURN_IN_FUNCTION_WITH_BLOCK_BODY!>}<!>

compiler/testData/diagnostics/tests/inference/regressions/kt2505.kt

@@ -6,8 +6,8 @@ trait MyType {}
 class MyClass<T> : MyType {}
 
 public open class HttpResponse() {
-    public open fun parseAs<T>(dataClass : MyClass<T>) : T? {
-        return null
+    public open fun parseAs<T>(dataClass : MyClass<T>) : T {
+        throw Exception()
     }
     public open fun parseAs(dataType : MyType) : Any? {
         return null
@@ -16,5 +16,5 @@ public open class HttpResponse() {
 
 fun test<R> (httpResponse: HttpResponse, rtype: MyClass<R>) {
     val res = httpResponse.parseAs( rtype )
-    res : R? //type mismatch: required R?, found T?
+    res : R //type mismatch: required R, found T
 }

compiler/testData/diagnostics/tests/inference/regressions/kt702.kt

@@ -6,7 +6,7 @@ fun getJavaClass<T>() : java.lang.Class<T> { <!NO_RETURN_IN_FUNCTION_WITH_BLOCK_
 
 public class Throwables() {
     class object {
-        public fun propagateIfInstanceOf<X : Throwable?>(throwable : Throwable?, declaredType : Class<X?>?) : Unit {
+        public fun propagateIfInstanceOf<X : Throwable?>(throwable : Throwable?, declaredType : Class<X<!BASE_WITH_NULLABLE_UPPER_BOUND!>?<!>>?) : Unit {
             if (((throwable != null) && declaredType?.isInstance(throwable)!!))
             {
                 throw declaredType?.cast(throwable)!!

compiler/testData/diagnostics/tests/inference/varargs/varargsAndPair.kt

@@ -1,4 +1,4 @@
-fun foo<T>(vararg <!UNUSED_PARAMETER!>ts<!>: T): T? = null
+fun foo<T: Any>(vararg <!UNUSED_PARAMETER!>ts<!>: T): T? = null
 
 class Pair<A>(a: A)