KT-9835 Completion thinks receiver is nullable when it is not

#KT-9835 Fixed

idea/ide-common/src/org/jetbrains/kotlin/idea/util/FuzzyType.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.Constrain
 import org.jetbrains.kotlin.types.*
 import org.jetbrains.kotlin.types.checker.StrictEqualityTypeChecker
 import org.jetbrains.kotlin.types.typeUtil.*
+import org.jetbrains.kotlin.utils.addToStdlib.check
 import java.util.*
 
 fun CallableDescriptor.fuzzyReturnType() = returnType?.toFuzzyType(typeParameters)
@@ -170,13 +171,20 @@ class FuzzyType(
         if (otherSubstitutedType.isError) return TypeSubstitutor.EMPTY
         if (!substitutedType.checkInheritance(otherSubstitutedType)) return null
 
-        val substitution = constraintSystem.typeVariables.map { it.originalTypeParameter }.associateBy({ it.typeConstructor }) {
-            val type = it.defaultType
-            val solution = substitutor.substitute(type, Variance.INVARIANT)
-            TypeProjectionImpl(if (solution != null && !ErrorUtils.containsUninferredParameter(solution)) solution else type)
-        }
+        val substitutorToKeepCapturedTypes = object : DelegatedTypeSubstitution(substitutor.substitution) {
+            override fun approximateCapturedTypes() = false
+        }.buildSubstitutor()
 
-        return TypeSubstitutor.create(TypeConstructorSubstitution.createByConstructorsMap(substitution))
+        val substitutionMap: Map<TypeConstructor, TypeProjection> = constraintSystem.typeVariables
+                .map { it.originalTypeParameter }
+                .associateBy(
+                        keySelector = { it.typeConstructor },
+                        valueTransform = {
+                            val typeProjection = TypeProjectionImpl(Variance.INVARIANT, it.defaultType)
+                            val substitutedProjection = substitutorToKeepCapturedTypes.substitute(typeProjection)
+                            substitutedProjection?.check { !ErrorUtils.containsUninferredParameter(it.type) } ?: typeProjection
+                        })
+        return TypeConstructorSubstitution.createByConstructorsMap(substitutionMap, approximateCapturedTypes = true).buildSubstitutor()
     }
 }
 

idea/ide-common/src/org/jetbrains/kotlin/idea/util/extensionsUtils.kt

@@ -27,8 +27,8 @@ import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowInfo
 import org.jetbrains.kotlin.resolve.calls.smartcasts.SmartCastManager
 import org.jetbrains.kotlin.resolve.scopes.LexicalScope
 import org.jetbrains.kotlin.resolve.scopes.receivers.ExpressionReceiver
-import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue
 import org.jetbrains.kotlin.resolve.scopes.receivers.ImplicitReceiver
+import org.jetbrains.kotlin.resolve.scopes.receivers.ReceiverValue
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.typeUtil.TypeNullability
 import org.jetbrains.kotlin.types.typeUtil.makeNotNullable
@@ -95,7 +95,9 @@ fun <TCallable : CallableDescriptor> TCallable.substituteExtensionIfCallable(
         return if (substitutors.any()) listOf(this) else listOf()
     }
     else {
-        return substitutors.map { @Suppress("UNCHECKED_CAST") (substitute(it) as TCallable) }.toList()
+        return substitutors
+                .mapNotNull { @Suppress("UNCHECKED_CAST") (substitute(it) as TCallable?) }
+                .toList()
     }
 }