From 6489ff2cb611cfe3d6bc5e88523732a3c4a450e1 Mon Sep 17 00:00:00 2001
From: Svetlana Isakova <svetlana.isakova@jetbrains.com>
Date: Fri, 19 Dec 2014 19:24:49 +0300
Subject: [PATCH] Ignore constraint from implicit 'in Nothing'

From Array<T> <: Array<out Int> we may generate T >: Nothing (implicit) and T <: Int (explicit).
Without ignoring we'll infer 'Nothing' for T too often
---
 .../ignoreConstraintFromImplicitInNothing.kt      | 15 +++++++++++++++
 .../ignoreConstraintFromImplicitInNothing.txt     | 12 ++++++++++++
 .../jet/checkers/JetDiagnosticsTestGenerated.java |  6 ++++++
 .../resolve/calls/inference/TypeBoundsImpl.kt     |  4 ----
 .../lang/types/checker/TypeCheckingProcedure.java |  7 ++++++-
 5 files changed, 39 insertions(+), 5 deletions(-)
 create mode 100644 compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.kt
 create mode 100644 compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.txt

diff --git a/compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.kt b/compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.kt
new file mode 100644
index 00000000000..8a53fcbb03a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.kt
@@ -0,0 +1,15 @@
+// !CHECK_TYPE
+// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
+
+class Foo<T>
+
+fun <T> foo1(f: (T) -> Unit): Foo<T> = Foo()
+inline fun <reified T> foo2(f: (T) -> Unit): Foo<T> = Foo()
+
+fun test1() {
+    val f1: Foo<out Int> = foo1 { it checkType { it : _<Int> } }
+    val f2: Foo<in Nothing> = foo1 { it <!UNREACHABLE_CODE!>checkType { it : _<Nothing> }<!> }
+
+    val f3: Foo<out Int> = foo2 { it checkType { it : _<Int> } }
+    val f4: Foo<in Nothing> = <!REIFIED_TYPE_FORBIDDEN_SUBSTITUTION!>foo2<!> { it <!UNREACHABLE_CODE!>checkType { it : _<Nothing> }<!> }
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.txt b/compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.txt
new file mode 100644
index 00000000000..6ba6b57c13f
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.txt
@@ -0,0 +1,12 @@
+package
+
+internal fun </*0*/ T> foo1(/*0*/ f: (T) -> kotlin.Unit): Foo<T>
+kotlin.inline() internal fun </*0*/ reified T> foo2(/*0*/ f: (T) -> kotlin.Unit): Foo<T>
+internal fun test1(): kotlin.Unit
+
+internal final class Foo</*0*/ T> {
+    public constructor Foo</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java
index dc17b4d80c9..9bcc864dae3 100644
--- a/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java
@@ -5181,6 +5181,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("ignoreConstraintFromImplicitInNothing.kt")
+                public void testIgnoreConstraintFromImplicitInNothing() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inference/constraints/ignoreConstraintFromImplicitInNothing.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("kt6320.kt")
                 public void testKt6320() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inference/constraints/kt6320.kt");
diff --git a/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeBoundsImpl.kt b/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeBoundsImpl.kt
index fbe6eb356f3..d56fcef04e5 100644
--- a/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeBoundsImpl.kt
+++ b/core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/TypeBoundsImpl.kt
@@ -160,10 +160,6 @@ public class TypeBoundsImpl(
         // a captured type might be an answer
         if (!possibleAnswer.getConstructor().isDenotable() && !possibleAnswer.isCaptured()) return false
 
-        // e.g. if T has a lower bound 'Nothing' and an upper bound 'String',
-        // by default 'Nothing' is inferred which can lead to an error for reified type variable
-        if (typeVariable.isReified() && possibleAnswer.cannotBeReified()) return false
-
         for (bound in bounds) {
             when (bound.kind) {
                 LOWER_BOUND -> if (!JetTypeChecker.DEFAULT.isSubtypeOf(bound.constrainingType, possibleAnswer)) {
diff --git a/core/descriptors/src/org/jetbrains/jet/lang/types/checker/TypeCheckingProcedure.java b/core/descriptors/src/org/jetbrains/jet/lang/types/checker/TypeCheckingProcedure.java
index d5b96b0e993..5400d85ddfa 100644
--- a/core/descriptors/src/org/jetbrains/jet/lang/types/checker/TypeCheckingProcedure.java
+++ b/core/descriptors/src/org/jetbrains/jet/lang/types/checker/TypeCheckingProcedure.java
@@ -244,7 +244,12 @@ public class TypeCheckingProcedure {
             }
             else {
                 if (!constraints.assertSubtype(subOut, superOut, this)) return false;
-                if (!constraints.assertSubtype(superIn, subIn, this)) return false;
+                if (superArgument.getProjectionKind() != Variance.OUT_VARIANCE) {
+                    if (!constraints.assertSubtype(superIn, subIn, this)) return false;
+                }
+                else {
+                    assert KotlinBuiltIns.isNothing(superIn) : "In component must be Nothing for out-projection";
+                }
             }
         }
         return true;