Delegation and nullability turned into capabilities

Otherwise they did not sustain substitutions

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

@@ -31,15 +31,13 @@ class DynamicTypesAllowed: DynamicTypesSettings() {
 
 trait Dynamicity : TypeCapability
 
+// Object is created only for convenience here. Dynamic types may occur in the form of DelegatingFlexibleTypes,
+// which are produced by substitutions
 object DynamicType : DelegatingFlexibleType(
         KotlinBuiltIns.getInstance().getNothingType(),
         KotlinBuiltIns.getInstance().getNullableAnyType(),
         DynamicTypeCapabilities
-) {
-    override fun getDelegate() = upperBound
-
-    override fun isNullable() = false
-}
+)
 
 fun JetType.isDynamic(): Boolean = this.getCapability(javaClass<Dynamicity>()) != null
 
@@ -49,12 +47,13 @@ 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 as T
+            return Impl(flexibility) as T
         else return null
     }
 
 
-    private object Impl : Dynamicity, Specificity, NullAwareness {
+    private class Impl(flexibility: Flexibility) : Dynamicity, Specificity, NullAwareness, FlexibleTypeDelegation {
+        override val delegateType: JetType = flexibility.upperBound
 
         override fun getSpecificityRelationTo(otherType: JetType): Specificity.Relation {
             return if (!otherType.isDynamic()) Specificity.Relation.LESS_SPECIFIC else Specificity.Relation.DONT_KNOW
@@ -64,5 +63,7 @@ public object DynamicTypeCapabilities : FlexibleTypeCapabilities {
             // Nullability has no effect on dynamics
             return DynamicType
         }
+
+        override fun computeIsNullable() = false
     }
 }

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

@@ -90,6 +90,7 @@ public fun JetType.upperIfFlexible(): JetType = if (this.isFlexible()) this.flex
 
 public trait NullAwareness : TypeCapability {
     public fun makeNullableAsSpecified(nullable: Boolean): JetType
+    public fun computeIsNullable(): Boolean
 }
 
 public trait Approximation : TypeCapability {
@@ -124,12 +125,15 @@ public fun JetType.getApproximationTo(
         extras: Approximation.DataFlowExtras = Approximation.DataFlowExtras.EMPTY
 ): Approximation.Info? = this.getCapability(javaClass<Approximation>())?.approximateToExpectedType(expectedType, extras)
 
+trait FlexibleTypeDelegation : TypeCapability {
+    public val delegateType: JetType
+}
 
 public open class DelegatingFlexibleType protected (
         override val lowerBound: JetType,
         override val upperBound: JetType,
         override val extraCapabilities: FlexibleTypeCapabilities
-) : DelegatingType(), NullAwareness, Flexibility, Approximation {
+) : DelegatingType(), NullAwareness, Flexibility, FlexibleTypeDelegation, Approximation {
     class object {
         platformStatic fun create(lowerBound: JetType, upperBound: JetType, extraCapabilities: FlexibleTypeCapabilities): JetType {
             if (lowerBound == upperBound) return lowerBound
@@ -157,6 +161,10 @@ public open class DelegatingFlexibleType protected (
                 extraCapabilities)
     }
 
+    override fun computeIsNullable() = delegateType.isNullable()
+
+    override fun isNullable(): Boolean = getCapability(javaClass<NullAwareness>())!!.computeIsNullable()
+
     override fun approximateToExpectedType(expectedType: JetType, dataFlowExtras: Approximation.DataFlowExtras): Approximation.Info? {
         // val foo: Any? = foo() : Foo!
         if (JetTypeChecker.DEFAULT.isSubtypeOf(upperBound, expectedType)) return null
@@ -171,7 +179,9 @@ public open class DelegatingFlexibleType protected (
         return Approximation.Info(this, expectedType, dataFlowExtras.presentableText)
     }
 
-    override fun getDelegate() = lowerBound
+    override val delegateType: JetType = lowerBound
+
+    override fun getDelegate() = getCapability(javaClass<FlexibleTypeDelegation>())!!.delegateType
 
     override fun toString() = "('$lowerBound'..'$upperBound')"
 }