FIR checker: report SMARTCAST_IMPOSSIBLE for local variables

compiler/testData/diagnostics/tests/smartCasts/variables/capturedByAtLeastOnce.kt

@@ -0,0 +1,56 @@
+import kotlin.contracts.*
+
+@Suppress("EXPERIMENTAL_API_USAGE_ERROR")
+inline fun atLeastOnce(block: () -> Unit) {
+    contract {
+        callsInPlace(block, InvocationKind.AT_LEAST_ONCE)
+    }
+    block()
+}
+
+@Suppress("EXPERIMENTAL_API_USAGE_ERROR")
+inline fun atMostOnce(block: () -> Unit) {
+    contract {
+        callsInPlace(block, InvocationKind.AT_MOST_ONCE)
+    }
+    block()
+}
+
+@Suppress("EXPERIMENTAL_API_USAGE_ERROR")
+inline fun exactlyOnce(block: () -> Unit) {
+    contract {
+        callsInPlace(block, InvocationKind.EXACTLY_ONCE)
+    }
+    block()
+}
+
+fun test() {
+    var s: String? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>null<!>
+    s = ""
+    atLeastOnce {
+        <!SMARTCAST_IMPOSSIBLE!>s<!>.length // unstable since lambda can be called twice
+        s = null
+        var s2: String? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>null<!>
+        s2 = ""
+        <!DEBUG_INFO_SMARTCAST!>s2<!>.length // local variable declared inside lambda is stable
+        s2 = null
+    }
+    s = ""
+    exactlyOnce {
+        <!SMARTCAST_IMPOSSIBLE!>s<!>.length // stable since lambda can be called only once
+        s = null
+        var s2: String? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>null<!>
+        s2 = ""
+        <!SMARTCAST_IMPOSSIBLE!>s2<!>.length // local variable declared inside lambda is stable
+        s2 = null
+    }
+    s = ""
+    atMostOnce {
+        <!SMARTCAST_IMPOSSIBLE!>s<!>.length // stable since lambda can be called at most once
+        s = null
+        var s2: String? = <!VARIABLE_WITH_REDUNDANT_INITIALIZER!>null<!>
+        s2 = ""
+        <!SMARTCAST_IMPOSSIBLE!>s2<!>.length // local variable declared inside lambda is stable
+        s2 = null
+    }
+}