From 4ab6b6954d41668c6e52d92052a07857a03809f8 Mon Sep 17 00:00:00 2001
From: Denis Zharkov <denis.zharkov@jetbrains.com>
Date: Wed, 18 Jan 2017 18:20:19 +0300
Subject: [PATCH] Fix false positive "Null can not be a value of a non-null
 type"

Inferred type of receiver of orElse  is Optional<T & Any>
Generic descriptor is orElse(E!): E!
Substituted descriptor is orElse(T): T , and that is the problem.

Seems that E!  => (T & Any)!  gets expanded to just T  or T & Any , however it should be expanded to
(T & Any) .. (T & Any)?  => T & Any .. T & Any

T & Any is NotNullTypeParameter(T)

The problem is that (T & Any)?  is expanded to T & Any,
that is seems to be wrong.

 #KT-15236 Fixed
---
 .../diagnostics/testsWithJava8/nullForOptionalOrElse.kt    | 7 +++++++
 .../diagnostics/testsWithJava8/nullForOptionalOrElse.txt   | 3 +++
 .../kotlin/checkers/DiagnosticsWithJava8TestGenerated.java | 6 ++++++
 .../kotlin/load/java/typeEnhancement/typeEnhancement.kt    | 3 ++-
 4 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.kt
 create mode 100644 compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.txt

diff --git a/compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.kt b/compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.kt
new file mode 100644
index 00000000000..e27ded0f05b
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.kt
@@ -0,0 +1,7 @@
+import java.util.*
+import java.util.stream.Stream
+
+fun <T> Stream<T>?.getIfSingle() =
+        this?.map { Optional.ofNullable(it) }
+        ?.reduce(Optional.empty()) { _, _ -> Optional.empty() }
+        ?.orElse(null) // <<---- should not be an error
diff --git a/compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.txt b/compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.txt
new file mode 100644
index 00000000000..fecbc90fedf
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.txt
@@ -0,0 +1,3 @@
+package
+
+public fun </*0*/ T> java.util.stream.Stream<T>?.getIfSingle(): T?
diff --git a/compiler/tests-java8/tests/org/jetbrains/kotlin/checkers/DiagnosticsWithJava8TestGenerated.java b/compiler/tests-java8/tests/org/jetbrains/kotlin/checkers/DiagnosticsWithJava8TestGenerated.java
index a73b51f2b73..a2e0435d6f7 100644
--- a/compiler/tests-java8/tests/org/jetbrains/kotlin/checkers/DiagnosticsWithJava8TestGenerated.java
+++ b/compiler/tests-java8/tests/org/jetbrains/kotlin/checkers/DiagnosticsWithJava8TestGenerated.java
@@ -48,6 +48,12 @@ public class DiagnosticsWithJava8TestGenerated extends AbstractDiagnosticsWithFu
         doTest(fileName);
     }
 
+    @TestMetadata("nullForOptionalOrElse.kt")
+    public void testNullForOptionalOrElse() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJava8/nullForOptionalOrElse.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("samWithConsumer.kt")
     public void testSamWithConsumer() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/testsWithJava8/samWithConsumer.kt");
diff --git a/core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/typeEnhancement/typeEnhancement.kt b/core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/typeEnhancement/typeEnhancement.kt
index a63fa53e5a2..ae8d9af53d7 100644
--- a/core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/typeEnhancement/typeEnhancement.kt
+++ b/core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/typeEnhancement/typeEnhancement.kt
@@ -243,7 +243,8 @@ internal class NotNullTypeParameter(override val delegate: SimpleType) : CustomT
     }
 
     override fun replaceAnnotations(newAnnotations: Annotations) = NotNullTypeParameter(delegate.replaceAnnotations(newAnnotations))
-    override fun makeNullableAsSpecified(newNullability: Boolean) = this
+    override fun makeNullableAsSpecified(newNullability: Boolean) =
+        if (newNullability) delegate.makeNullableAsSpecified(true) else this
 
     override val isError: Boolean
         get() = false