KT-13780 No completion and assertion error in log

#KT-13780 Fixed

core/descriptors/src/org/jetbrains/kotlin/descriptors/ClassConstructorDescriptor.kt

@@ -24,7 +24,7 @@ interface ClassConstructorDescriptor : ConstructorDescriptor {
 
     override fun getOriginal(): ClassConstructorDescriptor
 
-    override fun substitute(substitutor: TypeSubstitutor): ClassConstructorDescriptor
+    override fun substitute(substitutor: TypeSubstitutor): ClassConstructorDescriptor?
 
     override fun copy(
             newOwner: DeclarationDescriptor,

core/descriptors/src/org/jetbrains/kotlin/descriptors/ConstructorDescriptor.java

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.descriptors;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.types.KotlinType;
 import org.jetbrains.kotlin.types.TypeSubstitutor;
@@ -43,7 +44,7 @@ public interface ConstructorDescriptor extends FunctionDescriptor {
     @Override
     ConstructorDescriptor getOriginal();
 
-    @NotNull
+    @Nullable
     @Override
     ConstructorDescriptor substitute(@NotNull TypeSubstitutor substitutor);
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/FunctionDescriptor.java

@@ -19,7 +19,6 @@ package org.jetbrains.kotlin.descriptors;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.descriptors.annotations.Annotations;
-import org.jetbrains.kotlin.descriptors.impl.FunctionDescriptorImpl;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.types.KotlinType;
 import org.jetbrains.kotlin.types.TypeSubstitution;
@@ -37,7 +36,7 @@ public interface FunctionDescriptor extends CallableMemberDescriptor {
     @Override
     FunctionDescriptor getOriginal();
 
-    @NotNull
+    @Nullable
     @Override
     FunctionDescriptor substitute(@NotNull TypeSubstitutor substitutor);
 

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/ClassConstructorDescriptorImpl.java

@@ -106,7 +106,7 @@ public class ClassConstructorDescriptorImpl extends FunctionDescriptorImpl imple
         return (ClassConstructorDescriptor) super.getOriginal();
     }
 
-    @NotNull
+    @Nullable
     @Override
     public ClassConstructorDescriptor substitute(@NotNull TypeSubstitutor originalSubstitutor) {
         return (ClassConstructorDescriptor) super.substitute(originalSubstitutor);