Added tests for obsolete tasks

compiler/testData/diagnostics/tests/smartCasts/inference/kt1275.kt

@@ -0,0 +1,11 @@
+// !CHECK_TYPE
+
+fun foo(s : String?, b : Boolean) {
+    if (s == null) return
+
+    val s1 = if (b) "" else <!DEBUG_INFO_SMARTCAST!>s<!>
+    s1 checkType { _<String>() }
+
+    val s2 = s
+    <!DEBUG_INFO_SMARTCAST!>s2<!> checkType { _<String>() }
+}

compiler/testData/diagnostics/tests/smartCasts/inference/kt1275.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun foo(/*0*/ s: kotlin.String?, /*1*/ b: kotlin.Boolean): kotlin.Unit