Retain data flow info after array accesses

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayExpression.kt

@@ -0,0 +1,5 @@
+fun foo(arr: Array<out Number>): Int {
+    val result = (arr as Array<Int>)[0]
+    arr : Array<Int>
+    return result
+}

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayGetSetConvention.kt

@@ -0,0 +1,26 @@
+trait G {
+    fun get(x: Int, y: Int): Int = x + y
+    fun set(x: Int, y: Int, value: Int) {}
+}
+
+fun foo1(a: Int?, b: G) {
+    b[a!!, a<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>] = a
+    a : Int
+}
+
+fun foo2(a: Int?, b: G) {
+    b[0, a!!] = a
+    a : Int
+}
+
+fun foo3(a: Int?, b: G) {
+    val r = b[a!!, a]
+    a : Int
+    r : Int
+}
+
+fun foo4(a: Int?, b: G) {
+    val r = b[0, a!!]
+    a : Int
+    r : Int
+}

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/ArrayIndices.kt

@@ -0,0 +1,9 @@
+fun foo1(a: Int?, b: Array<Array<Int>>) {
+    b[a!!][a<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>] = a
+    a : Int
+}
+
+fun foo2(a: Int?, b: Array<Array<Int>>) {
+    b[0][a!!] = a
+    a : Int
+}

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/AssignmentToArrayElement.kt

@@ -0,0 +1,10 @@
+fun arrayAccessRHS(a: Int?, b: Array<Int>) {
+    b[0] = a!!
+    a : Int
+}
+
+fun arrayAccessLHS(a: Int?, b: Array<Int>) {
+    b[a!!] = a
+    a : Int
+}
+