KT-2643 Support multi-declarations in Data-Flow analysis

#KT-2643 fixed

compiler/testData/diagnostics/tests/declarationChecks/kt2643MultiDeclInControlFlow.kt

@@ -0,0 +1,27 @@
+//KT-2643 Support multi-declarations in Data-Flow analysis
+package n
+
+class C {
+    fun component1() = 1
+    fun component2() = 2
+}
+
+fun test1(c: C) {
+    val (<!UNUSED_VARIABLE!>a<!>, <!UNUSED_VARIABLE!>b<!>) = c
+}
+
+fun test2(c: C) {
+    val (a, <!UNUSED_VARIABLE!>b<!>) = c
+    a + 3
+}
+
+fun test3(c: C) {
+    var (<!ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE!>a<!>, <!UNUSED_VARIABLE!>b<!>) = c
+    a = <!UNUSED_VALUE!>3<!>
+}
+
+fun test4(c: C) {
+    var (<!VARIABLE_WITH_REDUNDANT_INITIALIZER!>a<!>, <!UNUSED_VARIABLE!>b<!>) = c
+    a = 3
+    a + 1
+}