Add "Suspicious collection reassignment" inspection #KT-20626 Fixed

idea/testData/quickfix/suspiciousCollectionReassignment/joinWithInitializer/noInitializer.kt

@@ -0,0 +1,12 @@
+// "Join with initializer" "false"
+// TOOL: org.jetbrains.kotlin.idea.inspections.SuspiciousCollectionReassignmentInspection
+// ACTION: Replace overloaded operator with function call
+// ACTION: Replace with ordinary assignment
+// WITH_RUNTIME
+fun test(otherList: List<Int>) {
+    var list: List<Int>
+    list = createList()
+    list <caret>+= otherList
+}
+
+fun createList(): List<Int> = listOf(1, 2, 3)

idea/testData/quickfix/suspiciousCollectionReassignment/joinWithInitializer/notLocal.kt

@@ -0,0 +1,15 @@
+// "Join with initializer" "false"
+// TOOL: org.jetbrains.kotlin.idea.inspections.SuspiciousCollectionReassignmentInspection
+// ACTION: Replace overloaded operator with function call
+// ACTION: Replace with ordinary assignment
+// WITH_RUNTIME
+class Test {
+    var list = createList()
+
+    fun test(otherList: List<Int>) {
+        // comment
+        list <caret>+= otherList
+    }
+
+    fun createList(): List<Int> = listOf(1, 2, 3)
+}

idea/testData/quickfix/suspiciousCollectionReassignment/joinWithInitializer/simple.kt

@@ -0,0 +1,10 @@
+// "Join with initializer" "true"
+// TOOL: org.jetbrains.kotlin.idea.inspections.SuspiciousCollectionReassignmentInspection
+// WITH_RUNTIME
+fun test(otherList: List<Int>) {
+    var list = createList()
+    // comment
+    list <caret>+= otherList
+}
+
+fun createList(): List<Int> = listOf(1, 2, 3)

idea/testData/quickfix/suspiciousCollectionReassignment/joinWithInitializer/simple.kt.after

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+// "Join with initializer" "true"
+// TOOL: org.jetbrains.kotlin.idea.inspections.SuspiciousCollectionReassignmentInspection
+// WITH_RUNTIME
+fun test(otherList: List<Int>) {
+    var list = createList() + otherList<caret>
+    // comment
+}
+
+fun createList(): List<Int> = listOf(1, 2, 3)

idea/testData/quickfix/suspiciousCollectionReassignment/joinWithInitializer/used.kt

@@ -0,0 +1,15 @@
+// "Join with initializer" "false"
+// TOOL: org.jetbrains.kotlin.idea.inspections.SuspiciousCollectionReassignmentInspection
+// ACTION: Change type to mutable
+// ACTION: Replace overloaded operator with function call
+// ACTION: Replace with ordinary assignment
+// WITH_RUNTIME
+fun test(otherList: List<Int>) {
+    var list = createList()
+    foo(list)
+    list <caret>+= otherList
+}
+
+fun createList(): List<Int> = listOf(1, 2, 3)
+
+fun foo(list: List<Int>) {}