Front-end and back-end test for KT-7801

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

@@ -0,0 +1,7 @@
+// See also KT-7801
+class A
+
+fun <T> test(v: T): T {
+    val a: T = if (v !is A) v else v
+    return a
+}

compiler/testData/diagnostics/tests/smartCasts/genericIntersection.txt

@@ -0,0 +1,10 @@
+package
+
+public fun </*0*/ T> test(/*0*/ v: T): T
+
+public final class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}