Basic class members generation.

Split testData into 'classes' and 'expressions'.

compiler/testData/ir/irText/expressions/smartCasts.kt

@@ -0,0 +1,23 @@
+fun expectsString(s: String) {}
+fun expectsInt(i: Int) {}
+
+fun overloaded(s: String) = s
+fun overloaded(x: Any) = x
+
+fun test1(x: Any) {
+    if (x !is String) return
+    println(x.length)
+    expectsString(x)
+    expectsInt(x.length)
+    expectsString(overloaded(x))
+}
+
+fun test2(x: Any): String {
+    if (x !is String) return ""
+    return overloaded(x)
+}
+
+fun test3(x: Any): String {
+    if (x !is String) return ""
+    return x
+}