Postfix expression code generation fixed as per KT-7561.

A set of tests for KT-7561 on codegen side, including exotic inc() functions().
 #KT-7561 Fixed.

compiler/testData/codegen/box/increment/assignPlusOnSmartCast.kt

@@ -0,0 +1,8 @@
+public fun box() : String {
+    var i : Int?
+    i = 10
+    // assignPlus on a smart cast should work
+    i += 1
+
+    return if (11 == i) "OK" else "fail i = $i"
+}

compiler/testData/codegen/box/increment/postfixIncrementDoubleSmartCast.kt

@@ -0,0 +1,10 @@
+public fun box() : String {
+    var i : Int?
+    i = 10
+    // We have "double" smart cast here:
+    // first on i and second on i++
+    // Back-end should NOT think that both i and j are Int
+    val j: Int = i++
+
+    return if (j == 10 && 11 == i) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/postfixIncrementOnClass.kt

@@ -0,0 +1,12 @@
+trait Base
+class Derived: Base
+class Another: Base
+fun Base.inc(): Derived { return Derived() }
+
+public fun box() : String {
+    var i : Base
+    i = Another()
+    val j = i++
+
+    return if (j is Another && i is Derived) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/postfixIncrementOnClassSmartCast.kt

@@ -0,0 +1,11 @@
+open class Base
+class Derived: Base()
+fun Derived.inc(): Derived { return Derived() }
+
+public fun box() : String {
+    var i : Base
+    i = Derived()
+    val j = i++
+
+    return if (j is Derived && i is Derived) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/postfixIncrementOnShortSmartCast.kt

@@ -0,0 +1,8 @@
+public fun box() : String {
+    var i : Short?
+    i = 10
+    // Postfix increment on a smart casted short should work
+    val j = i++
+
+    return if (j!!.toInt() == 10 && i!!.toInt() == 11) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/postfixIncrementOnSmartCast.kt

@@ -0,0 +1,9 @@
+public fun box() : String {
+    var i : Int?
+    i = 10
+    // Postfix increment on a smart cast should work
+    // Specific: i.inc() type is Int but i and j types are both Int?
+    val j = i++
+
+    return if (j == 10 && 11 == i) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/postfixNotnullClassIncrement.kt

@@ -0,0 +1,12 @@
+class MyClass
+
+// In principle it is not correct, MyClass? is not a subtype of MyClass
+fun MyClass.inc(): MyClass? = null
+
+public fun box() : String {
+    var i : MyClass? 
+    i = MyClass()
+    val j = i++
+
+    return if (j is MyClass && null == i) "OK" else "fail i = $i j = $j"
+}

compiler/testData/codegen/box/increment/postfixNullableClassIncrement.kt

@@ -0,0 +1,11 @@
+class MyClass
+
+fun MyClass?.inc(): MyClass? = null
+
+public fun box() : String {
+    var i : MyClass? 
+    i = MyClass()
+    val j = i++
+
+    return if (j is MyClass && null == i) "OK" else "fail i = $i j = $j"
+}

compiler/testData/codegen/box/increment/postfixNullableIncrement.kt

@@ -0,0 +1,10 @@
+fun Int?.inc(): Int? = this
+
+fun init(): Int? { return 10 }
+
+public fun box() : String {
+    var i : Int? = init()
+    val j = i++
+
+    return if (j == 10 && 10 == i) "OK" else "fail i = $i j = $j"
+}

compiler/testData/codegen/box/increment/prefixIncrementOnClass.kt

@@ -0,0 +1,12 @@
+trait Base
+class Derived: Base
+class Another: Base
+fun Base.inc(): Derived { return Derived() }
+
+public fun box() : String {
+    var i : Base
+    i = Another()
+    val j = ++i
+
+    return if (j is Derived && i is Derived) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/prefixIncrementOnClassSmartCast.kt

@@ -0,0 +1,11 @@
+open class Base
+class Derived: Base()
+fun Derived.inc(): Derived { return Derived() }
+
+public fun box() : String {
+    var i : Base
+    i = Derived()
+    val j = ++i
+
+    return if (j is Derived && i is Derived) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/prefixIncrementOnSmartCast.kt

@@ -0,0 +1,8 @@
+public fun box() : String {
+    var i : Int?
+    i = 10
+    // Prefix increment on a smart cast should work
+    val j = ++i
+
+    return if (j == 11 && 11 == i) "OK" else "fail j = $j i = $i"
+}

compiler/testData/codegen/box/increment/prefixNotnullClassIncrement.kt

@@ -0,0 +1,12 @@
+class MyClass
+
+// In principle it is not correct, MyClass? is not a subtype of MyClass
+fun MyClass.inc(): MyClass? = null
+
+public fun box() : String {
+    var i : MyClass? 
+    i = MyClass()
+    val j = ++i
+
+    return if (j == null && null == i) "OK" else "fail i = $i j = $j"
+}

compiler/testData/codegen/box/increment/prefixNullableClassIncrement.kt

@@ -0,0 +1,11 @@
+class MyClass
+
+fun MyClass?.inc(): MyClass? = null
+
+public fun box() : String {
+    var i : MyClass? 
+    i = MyClass()
+    val j = ++i
+
+    return if (j == null && null == i) "OK" else "fail i = $i j = $j"
+}

compiler/testData/codegen/box/increment/prefixNullableIncrement.kt

@@ -0,0 +1,10 @@
+fun Int?.inc(): Int? = this
+
+fun init(): Int? { return 10 }
+
+public fun box() : String {
+    var i : Int? = init()
+    val j = ++i
+
+    return if (j == 10 && 10 == i) "OK" else "fail i = $i j = $j"
+}