Preserve type annotations on type parameter when substituting

Subsitute(@A T, T:@B String) = @B @A String

Nullability when loading Java:
Subsitute(@NotNull T, T:String) = @NotNull String
Subsitute(@NotNull T, T:String!) = @NotNull String
Subsitute(@NotNull T, T:String?) = @NotNull String

Subsitute(@Nullable T, T:String) = @Nullable String?
Subsitute(@Nullable T, T:String!) = @Nullable String?
Subsitute(@Nullable T, T:String?) = @Nullable String?

compiler/testData/diagnostics/tests/j+k/SupertypeArgumentsNullability-NotNull-SpecialTypes.kt

@@ -19,6 +19,5 @@ public class Y extends X<String> {
 
 fun main() {
     checkSubtype<Any>(Y().fooN())
-    Y().barN(null);
+    Y().barN(<!NULL_FOR_NONNULL_TYPE!>null<!>);
 }
-

compiler/testData/diagnostics/tests/j+k/SupertypeArgumentsNullability-NotNull-SpecialTypes.txt

@@ -20,9 +20,9 @@ public open class X</*0*/ T> {
 
 public open class Y : X<kotlin.String!> {
     public constructor Y()
-    public/*package*/ open override /*1*/ /*fake_override*/ fun barN(/*0*/ org.jetbrains.annotations.NotNull() a: kotlin.String!): kotlin.Unit
+    public/*package*/ open override /*1*/ /*fake_override*/ fun barN(/*0*/ org.jetbrains.annotations.NotNull() a: kotlin.String): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    org.jetbrains.annotations.NotNull() public/*package*/ open override /*1*/ /*fake_override*/ fun fooN(): kotlin.String!
+    org.jetbrains.annotations.NotNull() public/*package*/ open override /*1*/ /*fake_override*/ fun fooN(): kotlin.String
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }

compiler/testData/diagnostics/tests/j+k/SupertypeArgumentsNullability-NotNull-UserTypes.kt

@@ -19,6 +19,5 @@ public class Y extends X<A> {
 
 fun main() {
     checkSubtype<Any>(Y().fooN())
-    Y().barN(null);
+    Y().barN(<!NULL_FOR_NONNULL_TYPE!>null<!>);
 }
-

compiler/testData/diagnostics/tests/j+k/SupertypeArgumentsNullability-NotNull-UserTypes.txt

@@ -20,9 +20,9 @@ public open class X</*0*/ T> {
 
 public open class Y : X<A!> {
     public constructor Y()
-    public/*package*/ open override /*1*/ /*fake_override*/ fun barN(/*0*/ org.jetbrains.annotations.NotNull() a: A!): kotlin.Unit
+    public/*package*/ open override /*1*/ /*fake_override*/ fun barN(/*0*/ org.jetbrains.annotations.NotNull() a: A): kotlin.Unit
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    org.jetbrains.annotations.NotNull() public/*package*/ open override /*1*/ /*fake_override*/ fun fooN(): A!
+    org.jetbrains.annotations.NotNull() public/*package*/ open override /*1*/ /*fake_override*/ fun fooN(): A
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }

compiler/testData/diagnostics/tests/platformTypes/typeEnhancement/saveAnnotationAfterSubstitution.kt

@@ -0,0 +1,47 @@
+// FILE: A.java
+
+import org.jetbrains.annotations.*;
+
+interface A<T> {
+    void foo(@NotNull T x, @Nullable T y);
+}
+
+// FILE: B1.java
+
+// contains fake_override fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?)
+interface B1 extends A<String> {}
+
+// FILE: B2.java
+import org.jetbrains.annotations.*;
+
+interface B2 extends A<String> {
+    // Ok, consistent override
+    // override fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?)
+    void foo(@NotNull String x, @Nullable String y);
+}
+
+// FILE: B3.java
+import org.jetbrains.annotations.*;
+
+interface B3 extends A<String> {
+    // inconsistent override, second parameter type is platform
+    // TODO: first one should be platform too, but it's not because when substituting T -> String!,
+    // value parameter type becomes platform and it can be overridden with @NotNull String.
+    // Conceptual problem: we can use type parameter as T?, but there is no way to specify same semantics as in Java `@NotNull T`.
+
+    // override /*1*/ fun foo(/*0*/ org.jetbrains.annotations.Nullable() x: kotlin.String?, /*1*/ org.jetbrains.annotations.NotNull() y: kotlin.String!): kotlin.Unit
+    void foo(@Nullable String x, @NotNull String y);
+}
+
+// FILE: main.kt
+
+// fake_override fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+interface C1 : A<String>
+
+// fake_override fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String?, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+interface C2 : A<String?>
+
+interface C3 : B1 {
+    // inconsistent override
+    <!NOTHING_TO_OVERRIDE!>override<!> fun foo(x: String?, y: String?);
+}

compiler/testData/diagnostics/tests/platformTypes/typeEnhancement/saveAnnotationAfterSubstitution.txt

@@ -0,0 +1,56 @@
+package
+
+public/*package*/ /*synthesized*/ fun </*0*/ T> A(/*0*/ function: (T!, T!) -> kotlin.Unit): A<T>
+public/*package*/ /*synthesized*/ fun B1(/*0*/ function: (kotlin.String!, kotlin.String?) -> kotlin.Unit): B1
+public/*package*/ /*synthesized*/ fun B2(/*0*/ function: (kotlin.String!, kotlin.String!) -> kotlin.Unit): B2
+public/*package*/ /*synthesized*/ fun B3(/*0*/ function: (kotlin.String!, kotlin.String!) -> kotlin.Unit): B3
+
+public/*package*/ interface A</*0*/ T> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: T, /*1*/ org.jetbrains.annotations.Nullable() y: T?): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public/*package*/ interface B1 : A<kotlin.String!> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public/*package*/ interface B2 : A<kotlin.String!> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public/*package*/ interface B3 : A<kotlin.String!> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ fun foo(/*0*/ org.jetbrains.annotations.Nullable() x: kotlin.String?, /*1*/ org.jetbrains.annotations.NotNull() y: kotlin.String!): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal interface C1 : A<kotlin.String> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal interface C2 : A<kotlin.String?> {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String?, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+internal interface C3 : B1 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ org.jetbrains.annotations.NotNull() x: kotlin.String, /*1*/ org.jetbrains.annotations.Nullable() y: kotlin.String?): kotlin.Unit
+    internal abstract fun foo(/*0*/ x: kotlin.String?, /*1*/ y: kotlin.String?): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/JetDiagnosticsTestGenerated.java

@@ -10463,6 +10463,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("saveAnnotationAfterSubstitution.kt")
+                public void testSaveAnnotationAfterSubstitution() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/typeEnhancement/saveAnnotationAfterSubstitution.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("supertypeDifferentParameterNullability.kt")
                 public void testSupertypeDifferentParameterNullability() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/typeEnhancement/supertypeDifferentParameterNullability.kt");

core/descriptors/src/org/jetbrains/kotlin/descriptors/annotations/Annotations.kt

@@ -69,6 +69,8 @@ class FilteredAnnotations(
 class CompositeAnnotations(
         private val delegates: List<Annotations>
 ) : Annotations {
+    constructor(vararg delegates: Annotations): this(delegates.toList())
+
     override fun isEmpty() = delegates.all { it.isEmpty() }
 
     override fun findAnnotation(fqName: FqName) = delegates.asSequence().map { it.findAnnotation(fqName) }.filterNotNull().firstOrNull()

core/descriptors/src/org/jetbrains/kotlin/types/TypeSubstitutor.java

@@ -20,6 +20,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor;
+import org.jetbrains.kotlin.descriptors.annotations.CompositeAnnotations;
 import org.jetbrains.kotlin.resolve.calls.inference.InferencePackage;
 import org.jetbrains.kotlin.resolve.scopes.SubstitutingScope;
 import org.jetbrains.kotlin.types.typeUtil.TypeUtilPackage;
@@ -221,6 +222,14 @@ public class TypeSubstitutor {
                 substitutedType = TypeUtils.makeNullableIfNeeded(replacement.getType(), type.isMarkedNullable());
             }
 
+            // substitutionType.annotations = replacement.annotations ++ type.annotations
+            if (!type.getAnnotations().isEmpty()) {
+                substitutedType = TypeUtilPackage.replaceAnnotations(
+                        substitutedType,
+                        new CompositeAnnotations(substitutedType.getAnnotations(), type.getAnnotations())
+                );
+            }
+
             Variance resultingProjectionKind = varianceConflict == VarianceConflictType.NO_CONFLICT
                                                ? combine(originalProjectionKind, replacement.getProjectionKind())
                                                : originalProjectionKind;

idea/src/org/jetbrains/kotlin/idea/inspections/UnusedReceiverParameterInspection.kt

@@ -95,7 +95,7 @@ public class UnusedReceiverParameterInspection : AbstractKotlinInspection() {
             return JetBundle.message("unused.receiver.parameter.remove")
         }
 
-        override fun applyFix(project: Project, descriptor: ProblemDescriptor?) {
+        override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
             declaration.setReceiverTypeReference(null)
         }
 

idea/src/org/jetbrains/kotlin/idea/inspections/UnusedSymbolInspection.kt

@@ -112,7 +112,7 @@ public class UnusedSymbolInspection : AbstractKotlinInspection() {
 
                     override fun getFamilyName() = "Safe delete"
 
-                    override fun applyFix(project: Project, descriptor: ProblemDescriptor?) {
+                    override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
                         if (!FileModificationService.getInstance().prepareFileForWrite(declaration.getContainingFile())) return
                         SafeDeleteHandler.invoke(project, arrayOf(declaration), false)
                     }