From 09b355af399eb9a265b4c57d138e4569365866ef Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 09:30:07 +0200
Subject: [PATCH 01/25] String is an object

---
 settings.gradle                                | 1 -
 src/main/kotlin/ru/kotlin/homework/generics.kt | 9 +++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 src/main/kotlin/ru/kotlin/homework/generics.kt

diff --git a/settings.gradle b/settings.gradle
index 1a97555..e9873b1 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -1,2 +1 @@
 rootProject.name = 'Kotlin7'
-
diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
new file mode 100644
index 0000000..28459c0
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -0,0 +1,9 @@
+@file:Suppress("RedundantExplicitType")
+
+package ru.kotlin.homework
+
+fun main() {
+    val str: String = "Some string"
+    val obj: Any = str
+    println("String as object: $obj")
+}
\ No newline at end of file

From 29634aeb0091118c8f4066840906cde2a85f81c5 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 09:33:22 +0200
Subject: [PATCH 02/25] String array is not an Object array

---
 src/main/kotlin/ru/kotlin/homework/generics.kt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index 28459c0..37d29a9 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -5,5 +5,9 @@ package ru.kotlin.homework
 fun main() {
     val str: String = "Some string"
     val obj: Any = str
+
+    val strArray: Array<String> = arrayOf(str)
+    val objArray: Array<Any> = strArray
+
     println("String as object: $obj")
 }
\ No newline at end of file

From 897538ddb3a68166b4cf544d41da5a00044ee271 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 09:34:59 +0200
Subject: [PATCH 03/25] String List is an Object list

---
 src/main/kotlin/ru/kotlin/homework/generics.kt | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index 37d29a9..31f369a 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -1,4 +1,4 @@
-@file:Suppress("RedundantExplicitType")
+@file:Suppress("RedundantExplicitType", "UNUSED_VARIABLE")
 
 package ru.kotlin.homework
 
@@ -6,8 +6,8 @@ fun main() {
     val str: String = "Some string"
     val obj: Any = str
 
-    val strArray: Array<String> = arrayOf(str)
-    val objArray: Array<Any> = strArray
+    val strList: List<String> = listOf(str)
+    val objList: List<Any> = strList
 
-    println("String as object: $obj")
+    println("List of objects: $objList")
 }
\ No newline at end of file

From 15203f3a09d09dbe2ab84fd67d53db24891a82b8 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 10:07:03 +0200
Subject: [PATCH 04/25] Color matcher

---
 src/main/kotlin/ru/kotlin/homework/Colors.kt  |  6 ++++++
 .../kotlin/ru/kotlin/homework/ShapeToColor.kt | 11 +++++++++++
 src/main/kotlin/ru/kotlin/homework/Shapes.kt  |  6 ++++++
 .../kotlin/ru/kotlin/homework/generics.kt     | 19 ++++++++++++-------
 4 files changed, 35 insertions(+), 7 deletions(-)
 create mode 100644 src/main/kotlin/ru/kotlin/homework/Colors.kt
 create mode 100644 src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
 create mode 100644 src/main/kotlin/ru/kotlin/homework/Shapes.kt

diff --git a/src/main/kotlin/ru/kotlin/homework/Colors.kt b/src/main/kotlin/ru/kotlin/homework/Colors.kt
new file mode 100644
index 0000000..3ec6d39
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/Colors.kt
@@ -0,0 +1,6 @@
+package ru.kotlin.homework
+
+abstract class Color
+
+data object Red : Color()
+data object Blue : Color()
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
new file mode 100644
index 0000000..5057ab8
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
@@ -0,0 +1,11 @@
+package ru.kotlin.homework
+
+import java.lang.IllegalArgumentException
+
+open class ShapeToColor {
+    open fun process(shape: Shape): Color = when(shape) {
+        is Square -> Red
+        is Circle -> Blue
+        else -> throw IllegalArgumentException("Unknown shape")
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/Shapes.kt b/src/main/kotlin/ru/kotlin/homework/Shapes.kt
new file mode 100644
index 0000000..505cdc9
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/Shapes.kt
@@ -0,0 +1,6 @@
+package ru.kotlin.homework
+
+abstract class Shape
+
+data object Square: Shape()
+data object Circle: Shape()
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index 31f369a..10597df 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -1,13 +1,18 @@
-@file:Suppress("RedundantExplicitType", "UNUSED_VARIABLE")
+@file:Suppress("RedundantExplicitType")
 
 package ru.kotlin.homework
 
-fun main() {
-    val str: String = "Some string"
-    val obj: Any = str
+import java.lang.IllegalArgumentException
+
+private val matcher: ShapeToColor = ShapeToColor()
 
-    val strList: List<String> = listOf(str)
-    val objList: List<Any> = strList
+fun main() {
+    println("Square: ${process(Square)}")
+    println("Circle: ${process(Circle)}")
+}
 
-    println("List of objects: $objList")
+fun process(shape: Shape) = when(matcher.process(shape)) {
+    Red -> "Красный"
+    Blue -> "Голубой"
+    else -> throw IllegalArgumentException("Неизвестный цвет")
 }
\ No newline at end of file

From d99aa8c2b9ab63e9ba2003481bdc4bece742a6eb Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 11:17:52 +0200
Subject: [PATCH 05/25] Narrow arguments

---
 src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt | 7 +++++++
 src/main/kotlin/ru/kotlin/homework/generics.kt     | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
index 5057ab8..1960514 100644
--- a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
+++ b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
@@ -8,4 +8,11 @@ open class ShapeToColor {
         is Circle -> Blue
         else -> throw IllegalArgumentException("Unknown shape")
     }
+}
+
+class CircleToColor : ShapeToColor() {
+    override fun process(shape: Shape): Color = when(shape) {
+        is Circle -> Blue
+        else -> throw IllegalArgumentException("Unknown shape")
+    }
 }
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index 10597df..1b5b5da 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -4,7 +4,7 @@ package ru.kotlin.homework
 
 import java.lang.IllegalArgumentException
 
-private val matcher: ShapeToColor = ShapeToColor()
+private val matcher: ShapeToColor = CircleToColor()
 
 fun main() {
     println("Square: ${process(Square)}")

From a5aa6b5703f1deb91d8de7d6b8232b12bd37d29c Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 11:26:11 +0200
Subject: [PATCH 06/25] Expand arguments

---
 src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt | 9 +++++++++
 src/main/kotlin/ru/kotlin/homework/Shapes.kt       | 3 ++-
 src/main/kotlin/ru/kotlin/homework/generics.kt     | 2 +-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
index 1960514..f08f459 100644
--- a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
+++ b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
@@ -1,3 +1,5 @@
+@file:Suppress("unused")
+
 package ru.kotlin.homework
 
 import java.lang.IllegalArgumentException
@@ -15,4 +17,11 @@ class CircleToColor : ShapeToColor() {
         is Circle -> Blue
         else -> throw IllegalArgumentException("Unknown shape")
     }
+}
+
+class NewShapeToColor : ShapeToColor() {
+    override fun process(shape: Shape): Color = when(shape) {
+        is Triangle -> Blue
+        else -> super.process(shape)
+    }
 }
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/Shapes.kt b/src/main/kotlin/ru/kotlin/homework/Shapes.kt
index 505cdc9..a8459bc 100644
--- a/src/main/kotlin/ru/kotlin/homework/Shapes.kt
+++ b/src/main/kotlin/ru/kotlin/homework/Shapes.kt
@@ -3,4 +3,5 @@ package ru.kotlin.homework
 abstract class Shape
 
 data object Square: Shape()
-data object Circle: Shape()
\ No newline at end of file
+data object Circle: Shape()
+data object Triangle: Shape()
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index 1b5b5da..526967b 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -4,7 +4,7 @@ package ru.kotlin.homework
 
 import java.lang.IllegalArgumentException
 
-private val matcher: ShapeToColor = CircleToColor()
+private val matcher: ShapeToColor = NewShapeToColor()
 
 fun main() {
     println("Square: ${process(Square)}")

From d4ec53b2bc8058039d80c8b2aa9d6d395bd05e39 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 11:49:30 +0200
Subject: [PATCH 07/25] Expand return values

---
 src/main/kotlin/ru/kotlin/homework/Colors.kt       | 3 ++-
 src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt | 8 ++++++++
 src/main/kotlin/ru/kotlin/homework/generics.kt     | 2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/Colors.kt b/src/main/kotlin/ru/kotlin/homework/Colors.kt
index 3ec6d39..6556466 100644
--- a/src/main/kotlin/ru/kotlin/homework/Colors.kt
+++ b/src/main/kotlin/ru/kotlin/homework/Colors.kt
@@ -3,4 +3,5 @@ package ru.kotlin.homework
 abstract class Color
 
 data object Red : Color()
-data object Blue : Color()
\ No newline at end of file
+data object Blue : Color()
+data object Green : Color()
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
index f08f459..148848c 100644
--- a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
+++ b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
@@ -24,4 +24,12 @@ class NewShapeToColor : ShapeToColor() {
         is Triangle -> Blue
         else -> super.process(shape)
     }
+}
+
+class NewColors : ShapeToColor() {
+    override fun process(shape: Shape): Color = when(shape) {
+        is Triangle -> Blue
+        is Square -> Green
+        else -> super.process(shape)
+    }
 }
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index 526967b..a3d59a8 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -4,7 +4,7 @@ package ru.kotlin.homework
 
 import java.lang.IllegalArgumentException
 
-private val matcher: ShapeToColor = NewShapeToColor()
+private val matcher: ShapeToColor = NewColors()
 
 fun main() {
     println("Square: ${process(Square)}")

From 208743151923544375e7dbc0127d65a2c241b434 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 12:01:59 +0200
Subject: [PATCH 08/25] Narrow return values

---
 src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt | 4 ++++
 src/main/kotlin/ru/kotlin/homework/generics.kt     | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
index 148848c..516e346 100644
--- a/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
+++ b/src/main/kotlin/ru/kotlin/homework/ShapeToColor.kt
@@ -32,4 +32,8 @@ class NewColors : ShapeToColor() {
         is Square -> Green
         else -> super.process(shape)
     }
+}
+
+class AllInRed : ShapeToColor() {
+    override fun process(shape: Shape): Color = Red
 }
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/generics.kt b/src/main/kotlin/ru/kotlin/homework/generics.kt
index a3d59a8..ed80015 100644
--- a/src/main/kotlin/ru/kotlin/homework/generics.kt
+++ b/src/main/kotlin/ru/kotlin/homework/generics.kt
@@ -4,7 +4,7 @@ package ru.kotlin.homework
 
 import java.lang.IllegalArgumentException
 
-private val matcher: ShapeToColor = NewColors()
+private val matcher: ShapeToColor = AllInRed()
 
 fun main() {
     println("Square: ${process(Square)}")

From 6ab8a1c4fd8701a25d694fead60e99e1188f445b Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 12:52:12 +0200
Subject: [PATCH 09/25] Contrvariance in Kotlin not allowed

---
 .../kotlin/homework/contrvarianceInKotlin.kt   | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt

diff --git a/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt b/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt
new file mode 100644
index 0000000..6925540
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt
@@ -0,0 +1,18 @@
+package ru.kotlin.homework
+
+fun main() {
+    val processor: ToExtendCircle = ToExtendCircle()
+    processor.process(Circle)
+}
+
+open class ToExtendCircle {
+    open fun process(value: Circle) {
+        println(value)
+    }
+}
+
+class ToExtendAny : ToExtendCircle() {
+    override fun process(value: Shape) {
+
+    }
+}
\ No newline at end of file

From 7227a067c6e1d23ebfa486bfdbd53c2a1f1362b7 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 13:24:28 +0200
Subject: [PATCH 10/25] Contrvariance with overloading

---
 .../ru/kotlin/homework/contrvarianceInKotlin.kt      | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt b/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt
index 6925540..1588223 100644
--- a/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt
+++ b/src/main/kotlin/ru/kotlin/homework/contrvarianceInKotlin.kt
@@ -1,8 +1,11 @@
 package ru.kotlin.homework
 
 fun main() {
-    val processor: ToExtendCircle = ToExtendCircle()
+    val processor: ToExtendCircle = ToExtendShape()
     processor.process(Circle)
+
+    val shapeProcessor: ToExtendShape = processor as ToExtendShape
+    shapeProcessor.process(Square)
 }
 
 open class ToExtendCircle {
@@ -11,8 +14,9 @@ open class ToExtendCircle {
     }
 }
 
-class ToExtendAny : ToExtendCircle() {
-    override fun process(value: Shape) {
-
+class ToExtendShape : ToExtendCircle() {
+    fun process(value: Shape) = when(value) {
+        is Circle -> super.process(value)
+        else -> println("Any: $value")
     }
 }
\ No newline at end of file

From 4935d07cc422aac70829656ecf9ccb12cc3ec568 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 13:35:25 +0200
Subject: [PATCH 11/25] Covariance

---
 .../ru/kotlin/homework/coVarianceInKotlin.kt  | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 src/main/kotlin/ru/kotlin/homework/coVarianceInKotlin.kt

diff --git a/src/main/kotlin/ru/kotlin/homework/coVarianceInKotlin.kt b/src/main/kotlin/ru/kotlin/homework/coVarianceInKotlin.kt
new file mode 100644
index 0000000..2e908a6
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/coVarianceInKotlin.kt
@@ -0,0 +1,19 @@
+package ru.kotlin.homework
+
+
+fun main() {
+    val producer: ShapeProducer = CircleProducer()
+    println(producer.produce())
+}
+
+open class ShapeProducer {
+    open fun produce(): Shape {
+        return Square
+    }
+}
+
+class CircleProducer : ShapeProducer() {
+    override fun produce(): Circle {
+        return Circle
+    }
+}
\ No newline at end of file

From 3abe99b5101fe49cdc9ce1744ee253881b1404a3 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 14:36:16 +0200
Subject: [PATCH 12/25] Invariant

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 src/main/kotlin/ru/kotlin/homework/inOut.kt

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
new file mode 100644
index 0000000..0036678
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -0,0 +1,19 @@
+package ru.kotlin.homework
+
+
+fun main() {
+    val circleGroup = Group<Circle>()
+    circleGroup.insert(Circle)
+    val fromGroup = circleGroup.fetch()
+    println("From group: $fromGroup")
+}
+
+open class Group<T> {
+    private val items: MutableList<T> = mutableListOf()
+    fun insert(item: T) {
+        items.add(item)
+    }
+    fun fetch(): T {
+        return items.last()
+    }
+}
\ No newline at end of file

From fc7a5b7d029d18682ed4a821f4a39c65d29cbe30 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 16:52:11 +0200
Subject: [PATCH 13/25] Circle group is not a Shape group

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index 0036678..68acc6f 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -6,6 +6,10 @@ fun main() {
     circleGroup.insert(Circle)
     val fromGroup = circleGroup.fetch()
     println("From group: $fromGroup")
+
+    val shapeGroup: Group<Shape> = circleGroup
+    val fromShapeGroup: Shape = shapeGroup.fetch()
+    println("From shape group: $fromShapeGroup")
 }
 
 open class Group<T> {

From f748ca47807889461dca410b828c3c4e6038aa36 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 16:53:57 +0200
Subject: [PATCH 14/25] Covariant read group

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index 68acc6f..262327b 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -7,17 +7,21 @@ fun main() {
     val fromGroup = circleGroup.fetch()
     println("From group: $fromGroup")
 
-    val shapeGroup: Group<Shape> = circleGroup
-    val fromShapeGroup: Shape = shapeGroup.fetch()
-    println("From shape group: $fromShapeGroup")
+    val readGroup: ReadGroup<Shape> = circleGroup
+    val fromReadGroup: Shape = readGroup.fetch()
+    println("From read group: $fromReadGroup")
 }
 
-open class Group<T> {
+interface ReadGroup<out T> {
+    fun fetch(): T
+}
+
+open class Group<T> : ReadGroup<T> {
     private val items: MutableList<T> = mutableListOf()
     fun insert(item: T) {
         items.add(item)
     }
-    fun fetch(): T {
+    override fun fetch(): T {
         return items.last()
     }
 }
\ No newline at end of file

From ccf543765cb512544125bcb49101071cbe9fa820 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Wed, 25 Oct 2023 17:03:44 +0200
Subject: [PATCH 15/25] Contrvariant write group

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index 262327b..f6f5c91 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -10,15 +10,28 @@ fun main() {
     val readGroup: ReadGroup<Shape> = circleGroup
     val fromReadGroup: Shape = readGroup.fetch()
     println("From read group: $fromReadGroup")
+
+    val shapeGroup = Group<Shape>()
+    val writeCircleGroup: WriteGroup<Circle> = shapeGroup
+    writeCircleGroup.insert(Circle)
+    val writeTriangleGroup: WriteGroup<Triangle> = shapeGroup
+    writeTriangleGroup.insert(Triangle)
+
+    val fromShapeGroup: Shape = shapeGroup.fetch()
+    println("From shape group: $fromShapeGroup")
 }
 
 interface ReadGroup<out T> {
     fun fetch(): T
 }
 
-open class Group<T> : ReadGroup<T> {
+interface WriteGroup<in T> {
+    fun insert(item: T)
+}
+
+open class Group<T> : ReadGroup<T>, WriteGroup<T> {
     private val items: MutableList<T> = mutableListOf()
-    fun insert(item: T) {
+    override fun insert(item: T) {
         items.add(item)
     }
     override fun fetch(): T {

From adf798155766c3f8149488045dec8d4398fda830 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 14:07:07 +0200
Subject: [PATCH 16/25] Declaration site variance

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index f6f5c91..0afeaae 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -7,34 +7,26 @@ fun main() {
     val fromGroup = circleGroup.fetch()
     println("From group: $fromGroup")
 
-    val readGroup: ReadGroup<Shape> = circleGroup
+    val readGroup: Group<out Shape> = circleGroup
     val fromReadGroup: Shape = readGroup.fetch()
     println("From read group: $fromReadGroup")
 
     val shapeGroup = Group<Shape>()
-    val writeCircleGroup: WriteGroup<Circle> = shapeGroup
+    val writeCircleGroup: Group<in Circle> = shapeGroup
     writeCircleGroup.insert(Circle)
-    val writeTriangleGroup: WriteGroup<Triangle> = shapeGroup
+    val writeTriangleGroup: Group<in Triangle> = shapeGroup
     writeTriangleGroup.insert(Triangle)
 
     val fromShapeGroup: Shape = shapeGroup.fetch()
     println("From shape group: $fromShapeGroup")
 }
 
-interface ReadGroup<out T> {
-    fun fetch(): T
-}
-
-interface WriteGroup<in T> {
-    fun insert(item: T)
-}
-
-open class Group<T> : ReadGroup<T>, WriteGroup<T> {
+open class Group<T> {
     private val items: MutableList<T> = mutableListOf()
-    override fun insert(item: T) {
+    fun insert(item: T) {
         items.add(item)
     }
-    override fun fetch(): T {
+    fun fetch(): T {
         return items.last()
     }
 }
\ No newline at end of file

From 55b58d80dc52f9ed198c017ab10698b404dee247 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 15:31:36 +0200
Subject: [PATCH 17/25] Declaration site variance with functions

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index 0afeaae..249bae9 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -10,12 +10,14 @@ fun main() {
     val readGroup: Group<out Shape> = circleGroup
     val fromReadGroup: Shape = readGroup.fetch()
     println("From read group: $fromReadGroup")
+    fetcher(circleGroup)
 
     val shapeGroup = Group<Shape>()
     val writeCircleGroup: Group<in Circle> = shapeGroup
     writeCircleGroup.insert(Circle)
     val writeTriangleGroup: Group<in Triangle> = shapeGroup
     writeTriangleGroup.insert(Triangle)
+    putter(shapeGroup, Circle)
 
     val fromShapeGroup: Shape = shapeGroup.fetch()
     println("From shape group: $fromShapeGroup")
@@ -29,4 +31,12 @@ open class Group<T> {
     fun fetch(): T {
         return items.last()
     }
+}
+
+fun fetcher(group: Group<out Shape>) {
+    val fetched = group.fetch()
+    println(fetched)
+}
+fun putter(group: Group<in Circle>, item: Circle) {
+    group.insert(item)
 }
\ No newline at end of file

From 7ce3fc5ed18c359b6eb85508e74a8ed8bb7b78da Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 15:50:59 +0200
Subject: [PATCH 18/25] Star projection

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index 249bae9..03eec4c 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -21,10 +21,17 @@ fun main() {
 
     val fromShapeGroup: Shape = shapeGroup.fetch()
     println("From shape group: $fromShapeGroup")
+
+    println(measure(circleGroup))
+    println(measure(readGroup))
+    println(measure(shapeGroup))
 }
 
 open class Group<T> {
     private val items: MutableList<T> = mutableListOf()
+
+    fun getSize(): Int = items.size
+
     fun insert(item: T) {
         items.add(item)
     }
@@ -39,4 +46,7 @@ fun fetcher(group: Group<out Shape>) {
 }
 fun putter(group: Group<in Circle>, item: Circle) {
     group.insert(item)
+}
+fun measure(group: Group<*>) {
+    println("Size of group: ${group.getSize()}")
 }
\ No newline at end of file

From 8db13b04d141ca3e92ad1d5fd7859bfc665aad7f Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 15:57:01 +0200
Subject: [PATCH 19/25] Star projection (explicit)

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index 03eec4c..c76fab1 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -22,9 +22,12 @@ fun main() {
     val fromShapeGroup: Shape = shapeGroup.fetch()
     println("From shape group: $fromShapeGroup")
 
-    println(measure(circleGroup))
-    println(measure(readGroup))
-    println(measure(shapeGroup))
+    var anyGroup: Group<*> = circleGroup
+    println(measure(anyGroup))
+    anyGroup = readGroup
+    println(measure(anyGroup))
+    anyGroup = shapeGroup
+    println(measure(anyGroup))
 }
 
 open class Group<T> {

From 68023c570cfed493c9214d3f8ac7dcffb21b70c9 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 19:13:25 +0200
Subject: [PATCH 20/25] Star projection: fetched is Any?

---
 src/main/kotlin/ru/kotlin/homework/Shapes.kt | 6 +++++-
 src/main/kotlin/ru/kotlin/homework/inOut.kt  | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/Shapes.kt b/src/main/kotlin/ru/kotlin/homework/Shapes.kt
index a8459bc..0d95ddb 100644
--- a/src/main/kotlin/ru/kotlin/homework/Shapes.kt
+++ b/src/main/kotlin/ru/kotlin/homework/Shapes.kt
@@ -1,6 +1,10 @@
 package ru.kotlin.homework
 
-abstract class Shape
+import kotlin.random.Random
+
+abstract class Shape {
+    val id: Int = Random.nextInt()
+}
 
 data object Square: Shape()
 data object Circle: Shape()
diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index c76fab1..fe4ffc8 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -28,6 +28,8 @@ fun main() {
     println(measure(anyGroup))
     anyGroup = shapeGroup
     println(measure(anyGroup))
+
+    idOfFetched(anyGroup)
 }
 
 open class Group<T> {
@@ -52,4 +54,8 @@ fun putter(group: Group<in Circle>, item: Circle) {
 }
 fun measure(group: Group<*>) {
     println("Size of group: ${group.getSize()}")
+}
+fun idOfFetched(group: Group<*>) {
+    val fetched: Any? = group.fetch()
+    println("No ID on fetched")
 }
\ No newline at end of file

From 837433445a014799af18cb1edcea57e4ca8ac513 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 19:14:20 +0200
Subject: [PATCH 21/25] Star projection on bound generic: fetched is Shape

---
 src/main/kotlin/ru/kotlin/homework/inOut.kt | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/inOut.kt b/src/main/kotlin/ru/kotlin/homework/inOut.kt
index fe4ffc8..b60b5b2 100644
--- a/src/main/kotlin/ru/kotlin/homework/inOut.kt
+++ b/src/main/kotlin/ru/kotlin/homework/inOut.kt
@@ -32,7 +32,7 @@ fun main() {
     idOfFetched(anyGroup)
 }
 
-open class Group<T> {
+open class Group<T : Shape> {
     private val items: MutableList<T> = mutableListOf()
 
     fun getSize(): Int = items.size
@@ -56,6 +56,6 @@ fun measure(group: Group<*>) {
     println("Size of group: ${group.getSize()}")
 }
 fun idOfFetched(group: Group<*>) {
-    val fetched: Any? = group.fetch()
-    println("No ID on fetched")
+    val fetched: Shape = group.fetch()
+    println("Id of fetched: ${fetched.id}")
 }
\ No newline at end of file

From 35ff416aa43cc253e48ab3296edfc49e29a2290d Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Thu, 26 Oct 2023 20:32:07 +0200
Subject: [PATCH 22/25] Home work

---
 README.md                                     | 24 +++++++
 .../kotlin/homework/network/NetworkLogger.kt  | 64 +++++++++++++++++++
 .../homework/network/NetworkResponse.kt       | 45 +++++++++++++
 3 files changed, 133 insertions(+)
 create mode 100644 src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt
 create mode 100644 src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt

diff --git a/README.md b/README.md
index c7da4e3..4c3dbb1 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,26 @@
 # Kotlin-7 - Generics
 Код к занятию Kotlin-7 - Generics
+
+## Домашнее задание
+В папке [network](src/main/kotlin/ru/kotlin/homework/network) находится прототип класса
+результата работы сетевого сервиса `NetworkResponse`, который может быть:
+
+- `Success` - для удачного результата
+- `Failure` - для ошибки
+
+### Задание 1.
+Исправьте определение классов так, чтобы все присваивания под определениями компилировались
+без ошибок. Подсказки:
+
+- Используйте declaration type variance
+- Мы только ВОЗВРАЩАЕМ результат или ошибку (ковариантность по обоим параметрам)
+- Вспоминаем, что тип Nothing - это подтип любого другого типа
+
+### Задание 2.
+Почините (правильно расставьте variance параметров) класс [NetworkLogger](src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt)
+таким образом, чтобы **один** универсальный экземпляр логгера можно было использовать для логирования любых ошибок:
+
+- `processThrowables` принимает `ErrorLogger<Throwable>`
+- `processApiErrors` принимает `ErrorLogger<ApiException>`
+
+Приступайте ко второму заданию только после окончания работы над первым!
\ No newline at end of file
diff --git a/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt b/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt
new file mode 100644
index 0000000..a5f33c5
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt
@@ -0,0 +1,64 @@
+@file:Suppress("unused")
+
+package ru.kotlin.homework.network
+
+import ru.kotlin.homework.Circle
+import java.lang.IllegalArgumentException
+import java.time.LocalDateTime
+
+/**
+ * Известный вам список ошибок
+ */
+sealed class ApiException(message: String) : Throwable(message) {
+    data object NotAuthorized : ApiException("Not authorized")
+    data object NetworkException : ApiException("Not connected")
+    data object UnknownException: ApiException("Unknown exception")
+}
+
+class ErrorLogger<E : Throwable> {
+
+    val errors = mutableListOf<Pair<LocalDateTime, E>>()
+
+    fun log(response: NetworkResponse<*, E>) {
+        if (response is Failure) {
+            errors.add(response.responseDateTime to response.error)
+        }
+    }
+
+    fun dumpLog() {
+        errors.forEach { (date, error) ->
+            println("Error at $date: ${error.message}")
+        }
+    }
+}
+
+fun processThrowables(logger: ErrorLogger<Throwable>) {
+    logger.log(Success("Success"))
+    Thread.sleep(100)
+    logger.log(Success(Circle))
+    Thread.sleep(100)
+    logger.log(Failure(IllegalArgumentException("Something unexpected")))
+
+    logger.dumpLog()
+}
+
+fun processApiErrors(apiExceptionLogger: ErrorLogger<ApiException>) {
+    apiExceptionLogger.log(Success("Success"))
+    Thread.sleep(100)
+    apiExceptionLogger.log(Success(Circle))
+    Thread.sleep(100)
+    apiExceptionLogger.log(Failure(ApiException.NetworkException))
+
+    apiExceptionLogger.dumpLog()
+}
+
+fun main() {
+    val logger = ErrorLogger<Throwable>()
+
+    println("Processing Throwable:")
+    processThrowables(logger)
+
+    println("Processing Api:")
+    processApiErrors(logger)
+}
+
diff --git a/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt b/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt
new file mode 100644
index 0000000..3018c40
--- /dev/null
+++ b/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt
@@ -0,0 +1,45 @@
+@file:Suppress("unused")
+
+package ru.kotlin.homework.network
+
+import java.lang.Exception
+import java.lang.IllegalArgumentException
+import java.time.LocalDateTime
+
+/**
+ * Network result
+ */
+sealed class NetworkResponse<T, R> {
+    val responseDateTime: LocalDateTime = LocalDateTime.now()
+}
+
+/**
+ * Network success
+ */
+data class Success<T, R>(val resp: T): NetworkResponse<T, R>()
+
+/**
+ * Network error
+ */
+data class Failure<T, R>(val error: R): NetworkResponse<T, R>()
+
+val s1 = Success("Message")
+val r11: NetworkResponse<String, Error> = s1
+val r12: NetworkResponse<Any, Error> = s1
+
+val s2 = Success("Message")
+val r21: NetworkResponse<String, Exception> = s2
+val r22: NetworkResponse<Any, Exception> = s2
+
+val s3 = Success(String())
+val r31: Success<CharSequence> = s3
+val r32: Success<Any> = s3
+
+val e = Failure(Error())
+val er1: NetworkResponse<String, Error> = e
+val er2: NetworkResponse<Any, Error> = e
+val er4: NetworkResponse<Any, Throwable> = e
+
+val er5: NetworkResponse<Int, Throwable> = Failure(IllegalArgumentException("message"))
+
+val message = e.error.message
\ No newline at end of file

From 99e8d1dfddbd8c34678a5b6446ebcd1626670d81 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Fri, 27 Oct 2023 12:07:49 +0200
Subject: [PATCH 23/25] Check action

---
 .github/workflows/check.yml | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 .github/workflows/check.yml

diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
new file mode 100644
index 0000000..9cffaf9
--- /dev/null
+++ b/.github/workflows/check.yml
@@ -0,0 +1,32 @@
+name: Check
+
+on:
+  pull_request:
+    types: [assigned, opened, synchronize, reopened]
+
+jobs:
+  checks:
+    name: Checks
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+    - name: set up JDK 17
+      uses: actions/setup-java@v1
+      with:
+        java-version: 17
+    - name: Cache
+      uses: actions/cache@v2
+      with:
+        path: |
+          ~/.gradle/caches
+          ~/.gradle/wrapper
+          ~/.m2
+          ~/.android/build-cache
+        key: ${GITHUB_REF##*/}
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Check with gradle
+      run: ./gradlew build

From a78143c5418f2e82bdcd52bf1163e0956e876b96 Mon Sep 17 00:00:00 2001
From: Nikolay Kochetkov <nkochetkov@jetsmarter.com>
Date: Fri, 27 Oct 2023 14:51:25 +0200
Subject: [PATCH 24/25] Additional homework

---
 README.md | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 4c3dbb1..d7a41ad 100644
--- a/README.md
+++ b/README.md
@@ -23,4 +23,11 @@
 - `processThrowables` принимает `ErrorLogger<Throwable>`
 - `processApiErrors` принимает `ErrorLogger<ApiException>`
 
-Приступайте ко второму заданию только после окончания работы над первым!
\ No newline at end of file
+Приступайте ко второму заданию только после окончания работы над первым!
+
+### Задание 3 (со звездочкой)
+Сделайте так, чтобы [NetworkLogger](src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt) имел возможность выдать список
+накопленных ошибок. Настройте типы таким образом, чтобы при сохранении условий заданий 1 и 2, в классе появилась функция:
+```kotlin
+fun dump(): List<Pair<LocalDateTime, E>>
+```
\ No newline at end of file

From 7872da92fa88f7fdacd7a28dcb1e718c0dc5b942 Mon Sep 17 00:00:00 2001
From: PavelSkobeev <pavel_skobeev@mail.ru>
Date: Tue, 4 Jun 2024 14:08:17 +0300
Subject: [PATCH 25/25] =?UTF-8?q?=D1=87=D1=82=D0=BE-=D1=82=D0=BE=20=D1=81?=
 =?UTF-8?q?=D0=B4=D0=B5=D0=BB=D0=B0=D0=BB?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt | 4 ++--
 .../kotlin/ru/kotlin/homework/network/NetworkResponse.kt    | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt b/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt
index a5f33c5..a997a09 100644
--- a/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt
+++ b/src/main/kotlin/ru/kotlin/homework/network/NetworkLogger.kt
@@ -32,7 +32,7 @@ class ErrorLogger<E : Throwable> {
     }
 }
 
-fun processThrowables(logger: ErrorLogger<Throwable>) {
+fun processThrowables(logger: ErrorLogger<in Throwable>) {
     logger.log(Success("Success"))
     Thread.sleep(100)
     logger.log(Success(Circle))
@@ -42,7 +42,7 @@ fun processThrowables(logger: ErrorLogger<Throwable>) {
     logger.dumpLog()
 }
 
-fun processApiErrors(apiExceptionLogger: ErrorLogger<ApiException>) {
+fun processApiErrors(apiExceptionLogger: ErrorLogger<in ApiException>) {
     apiExceptionLogger.log(Success("Success"))
     Thread.sleep(100)
     apiExceptionLogger.log(Success(Circle))
diff --git a/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt b/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt
index 3018c40..f35dbc2 100644
--- a/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt
+++ b/src/main/kotlin/ru/kotlin/homework/network/NetworkResponse.kt
@@ -9,19 +9,19 @@ import java.time.LocalDateTime
 /**
  * Network result
  */
-sealed class NetworkResponse<T, R> {
+sealed class NetworkResponse<out T, out R> {
     val responseDateTime: LocalDateTime = LocalDateTime.now()
 }
 
 /**
  * Network success
  */
-data class Success<T, R>(val resp: T): NetworkResponse<T, R>()
+data class Success<out T>(val resp: T): NetworkResponse<T, Nothing>()
 
 /**
  * Network error
  */
-data class Failure<T, R>(val error: R): NetworkResponse<T, R>()
+data class Failure<R>(val error: R): NetworkResponse<Nothing, R>()
 
 val s1 = Success("Message")
 val r11: NetworkResponse<String, Error> = s1