Complex augmented assignment test.

Fix string literal creation for empty string template.

compiler/testData/ir/irText/arrayAugmentedAssignment1.txt

@@ -1,4 +1,4 @@
-IrFile /augmentedAssignmentArray.kt
+IrFile /arrayAugmentedAssignment1.kt
   IrFunction public fun foo(): kotlin.IntArray
     IrExpressionBody
       BLOCK type=<no-type> hasResult=false isDesugared=true

compiler/testData/ir/irText/arrayAugmentedAssignment2.kt

@@ -0,0 +1,11 @@
+interface IA {
+    operator fun get(index: String): Int
+}
+
+interface IB {
+    operator fun IA.set(index: String, value: Int)
+}
+
+fun IB.test(a: IA) {
+    a[""] += 42
+}

compiler/testData/ir/irText/arrayAugmentedAssignment2.txt

@@ -0,0 +1,19 @@
+IrFile /arrayAugmentedAssignment2.kt
+  DUMMY IA
+  DUMMY IB
+  IrFunction public fun IB.test(/*0*/ a: IA): kotlin.Unit
+    IrExpressionBody
+      BLOCK type=<no-type> hasResult=false isDesugared=false
+        VAR val tmp0_array: IA
+          GET_VAR a type=IA
+        VAR val tmp1_index0: kotlin.String
+          LITERAL String type=kotlin.String value=''
+        CALL .set type=kotlin.Unit operator=PLUSEQ
+          $this: $RECEIVER of: test type=IB
+          $receiver: GET_VAR tmp0_array type=IA
+          index: GET_VAR tmp1_index0 type=kotlin.String
+          value: CALL .plus type=kotlin.Int operator=PLUSEQ
+            $this: CALL .get type=kotlin.Int operator=PLUSEQ
+              $this: GET_VAR tmp0_array type=IA
+              index: GET_VAR tmp1_index0 type=kotlin.String
+            other: LITERAL Int type=kotlin.Int value='42'

compiler/testData/ir/irText/smartCastsWithDestructuring.txt

@@ -10,7 +10,7 @@ IrFile /smartCastsWithDestructuring.kt
     IrExpressionBody
       BLOCK type=<no-type> hasResult=false isDesugared=true
         RETURN type=<no-type>
-          ? IrStringConcatenationExpressionImpl type=kotlin.String
+          LITERAL String type=kotlin.String value=''
   IrFunction public fun test(/*0*/ x: I1): kotlin.Unit
     IrExpressionBody
       BLOCK type=<no-type> hasResult=false isDesugared=false