Nullability of dynamic types

compiler/frontend/src/org/jetbrains/jet/lang/resolve/TypeResolver.kt

@@ -199,8 +199,9 @@ public class TypeResolver(
             }
 
             override fun visitNullableType(nullableType: JetNullableType) {
-                val baseType = resolveTypeElement(c, annotations, nullableType.getInnerType())
-                if (baseType.isNullable()) {
+                val innerType = nullableType.getInnerType()
+                val baseType = resolveTypeElement(c, annotations, innerType)
+                if (baseType.isNullable() || innerType is JetNullableType || innerType is JetDynamicType) {
                     c.trace.report(REDUNDANT_NULLABLE.on(nullableType))
                 }
                 else if (!baseType.isBare() && TypeUtils.hasNullableSuperType(baseType.getActualType())) {

compiler/testData/diagnostics/tests/dynamicTypes/nullable.kt

@@ -0,0 +1,11 @@
+// !CHECK_TYPE
+
+// MODULE[js]: m1
+// FILE: k.kt
+
+fun foo(dn: dynamic<!REDUNDANT_NULLABLE!>?<!>, d: dynamic, dnn: dynamic<!REDUNDANT_NULLABLE!>?<!><!REDUNDANT_NULLABLE!>?<!>) {
+    dn.checkType { it : _<dynamic>}
+    dn.checkType { it : _<dynamic<!REDUNDANT_NULLABLE!>?<!>>}
+    d.checkType { it : _<dynamic>}
+    d.checkType { it : _<dynamic<!REDUNDANT_NULLABLE!>?<!>>}
+}

compiler/testData/diagnostics/tests/dynamicTypes/nullable.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ dn: dynamic, /*1*/ d: dynamic): kotlin.Unit

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

@@ -3722,6 +3722,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("nullable.kt")
+            public void testNullable() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dynamicTypes/nullable.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("overloading.kt")
             public void testOverloading() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dynamicTypes/overloading.kt");

core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java

@@ -389,7 +389,7 @@ public class ConstraintSystemImpl implements ConstraintSystem {
 
         // can be equal for the recursive invocations:
         // fun <T> foo(i: Int) : T { ... return foo(i); } => T <: T
-        if (JetTypeChecker.DEFAULT.equalTypes(subType, superType)) return;
+        if (isMyTypeVariable(subType) && isMyTypeVariable(superType) && JetTypeChecker.DEFAULT.equalTypes(subType, superType)) return;
 
         assert !isMyTypeVariable(subType) || !isMyTypeVariable(superType) :
                 "The constraint shouldn't contain different type variables on both sides: " + subType + " <: " + superType;

core/descriptors/src/org/jetbrains/jet/lang/types/dynamicTypes.kt

@@ -37,6 +37,8 @@ object DynamicType : DelegatingFlexibleType(
         DynamicTypeCapabilities
 ) {
     override fun getDelegate() = upperBound
+
+    override fun isNullable() = false
 }
 
 fun JetType.isDynamic(): Boolean = this.getCapability(javaClass<Dynamicity>()) != null
@@ -47,18 +49,20 @@ public object DynamicTypeCapabilities : FlexibleTypeCapabilities {
     override fun <T : TypeCapability> getCapability(capabilityClass: Class<T>, jetType: JetType, flexibility: Flexibility): T? {
         if (capabilityClass.isAssignableFrom(javaClass<Impl>()))
             [suppress("UNCHECKED_CAST")]
-            return Impl(jetType, flexibility) as T
+            return Impl as T
         else return null
     }
 
 
-    private class Impl(val type: JetType, val flexibility: Flexibility) : Dynamicity, Specificity {
-
-        private val lowerBound: JetType get() = flexibility.lowerBound
-        private val upperBound: JetType get() = flexibility.upperBound
+    private object Impl : Dynamicity, Specificity, NullAwareness {
 
         override fun getSpecificityRelationTo(otherType: JetType): Specificity.Relation {
             return if (!otherType.isDynamic()) Specificity.Relation.LESS_SPECIFIC else Specificity.Relation.DONT_KNOW
         }
+
+        override fun makeNullableAsSpecified(nullable: Boolean): JetType {
+            // Nullability has no effect on dynamics
+            return DynamicType
+        }
     }
 }