Intrinsics for 'reversed': generate in-const-bound ranges as countable

#KT-21323 In Progress

compiler/testData/codegen/box/ranges/forInReversed/forInReversedEmptyRangeLiteralWithNonConstBounds.kt

@@ -0,0 +1,25 @@
+// WITH_RUNTIME
+import kotlin.test.*
+
+fun intLow() = 4
+fun intHigh() = 1
+fun longLow() = 4L
+fun longHigh() = 1L
+fun charLow() = '4'
+fun charHigh() = '1'
+
+fun box(): String {
+    for (i in (intLow() .. intHigh()).reversed()) {
+        throw AssertionError("Loop should not be executed")
+    }
+
+    for (i in (longLow() .. longHigh()).reversed()) {
+        throw AssertionError("Loop should not be executed")
+    }
+
+    for (i in (charLow() .. charHigh()).reversed()) {
+        throw AssertionError("Loop should not be executed")
+    }
+
+    return "OK"
+}

compiler/testData/codegen/box/ranges/forInReversed/forInReversedRangeLiteralWithNonConstBounds.kt

@@ -0,0 +1,31 @@
+// WITH_RUNTIME
+import kotlin.test.*
+
+fun intLow() = 1
+fun intHigh() = 4
+fun longLow() = 1L
+fun longHigh() = 4L
+fun charLow() = '1'
+fun charHigh() = '4'
+
+fun box(): String {
+    var sum = 0
+    for (i in (intLow() .. intHigh()).reversed()) {
+        sum = sum * 10 + i
+    }
+    assertEquals(4321, sum)
+
+    var sumL = 0L
+    for (i in (longLow() .. longHigh()).reversed()) {
+        sumL = sumL * 10 + i
+    }
+    assertEquals(4321L, sumL)
+
+    var sumC = 0
+    for (i in (charLow() .. charHigh()).reversed()) {
+        sumC = sumC * 10 + i.toInt() - '0'.toInt()
+    }
+    assertEquals(4321, sumC)
+
+    return "OK"
+}