[FIR] Adding a test case to show resolution of KT-29559 in K2

compiler/testData/diagnostics/tests/postfixIncSmartCast.fir.kt

@@ -0,0 +1,11 @@
+open class I {
+    operator fun inc(): ST = ST()
+}
+
+class ST : I()
+
+fun main() {
+    var local = I()
+    val x: ST = <!INITIALIZER_TYPE_MISMATCH!>local++<!>
+    val y: ST = local
+}

compiler/testData/diagnostics/tests/postfixIncSmartCast.kt

@@ -0,0 +1,11 @@
+open class I {
+    operator fun inc(): ST = ST()
+}
+
+class ST : I()
+
+fun main() {
+    var local = I()
+    val x: ST = <!TYPE_MISMATCH!>local++<!>
+    val y: ST = <!TYPE_MISMATCH!>local<!>
+}

compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.fir.kt

@@ -0,0 +1,27 @@
+// WITH_STDLIB
+// SKIP_TEXT
+// ISSUE: KT-29559
+
+fun consume(i: Int) {}
+fun consume(c: Char) {}
+fun consume(a: Any?) {}
+
+fun test1() {
+    var a: Any
+
+    a = 1
+    consume(a)
+
+    a = 1
+    consume(a++)
+
+    a = 1
+    consume(++a)
+
+    a = 't'
+    consume(a++)
+
+    a = 't'
+    consume(++a)
+    consume(a++)
+}

compiler/testData/diagnostics/tests/smartCasts/incrementAfterAssignment.kt

@@ -0,0 +1,27 @@
+// WITH_STDLIB
+// SKIP_TEXT
+// ISSUE: KT-29559
+
+fun consume(i: Int) {}
+fun consume(c: Char) {}
+fun consume(a: Any?) {}
+
+fun test1() {
+    var a: Any
+
+    a = 1
+    consume(<!DEBUG_INFO_SMARTCAST!>a<!>)
+
+    a = 1
+    consume(<!TYPE_MISMATCH!><!DEBUG_INFO_SMARTCAST!>a<!>++<!>)
+
+    a = 1
+    consume(++<!DEBUG_INFO_SMARTCAST!>a<!>)
+
+    a = 't'
+    consume(<!TYPE_MISMATCH!><!DEBUG_INFO_SMARTCAST!>a<!>++<!>)
+
+    a = 't'
+    consume(++<!DEBUG_INFO_SMARTCAST!>a<!>)
+    consume(<!DEBUG_INFO_SMARTCAST!><!DEBUG_INFO_SMARTCAST!>a<!>++<!>)
+}