[IR] Extend test coverage for smart cast handling.

compiler/testData/codegen/box/ieee754/smartCastToInt.kt

@@ -0,0 +1,8 @@
+fun test(x: Any?, y: Double) =
+    x is Int && x < y
+
+fun box(): String =
+    if (!test(0, -0.0))
+        "OK"
+    else
+        "Failed"

compiler/testData/codegen/box/smartCasts/multipleSmartCast.kt

@@ -0,0 +1,22 @@
+interface IC1 {
+    operator fun component1(): String
+}
+
+interface IC2 {
+    operator fun component2(): String
+}
+
+class A : IC1, IC2 {
+    override fun component1(): String = "O"
+    override fun component2(): String = "K"
+}
+
+fun test(x: Any): String {
+    if (x is IC1 && x is IC2) {
+        val (x1, x2) = x
+        return "$x1$x2"
+    }
+    return "FAIL"
+}
+
+fun box(): String = test(A())

compiler/testData/codegen/boxAgainstJava/sam/smartCastSamConversion.kt

@@ -0,0 +1,22 @@
+// FILE: test.kt
+fun test(a: Any) {
+    a as (String) -> String
+    J.use(a)
+}
+
+fun box(): String {
+    test({s: String? -> s})
+    return "OK"
+}
+
+// FILE: JFoo.java
+public interface JFoo<T> {
+    T foo(T x);
+}
+
+// FILE: J.java
+public class J {
+    public static void use(JFoo<String> jfoo) {
+        jfoo.foo(null);
+    }
+}