Handle arbitrary variable as assignment LHS

(e.g., conventional compound assignment for a parameter value).

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/AssignmentGenerator.kt

@@ -16,9 +16,7 @@
 
 package org.jetbrains.kotlin.psi2ir.generators
 
-import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.*
-import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
-import org.jetbrains.kotlin.descriptors.PropertyDescriptor
 import org.jetbrains.kotlin.descriptors.impl.LocalVariableDescriptor
 import org.jetbrains.kotlin.descriptors.impl.SyntheticFieldDescriptor
 import org.jetbrains.kotlin.ir.expressions.IrExpression
@@ -119,6 +117,8 @@ class AssignmentGenerator(statementGenerator: StatementGenerator) : StatementGen
                     VariableLValue(ktLeft.startOffset, ktLeft.endOffset, descriptor, operator)
             is PropertyDescriptor ->
                 generateAssignmentReceiverForProperty(descriptor, operator, ktLeft, resolvedCall)
+            is VariableDescriptor ->
+                VariableLValue(ktLeft.startOffset, ktLeft.endOffset, descriptor, operator)
             else ->
                 TODO("Other cases of LHS")
         }

compiler/testData/ir/irText/expressions/complexAugmentedAssignment.kt

@@ -18,3 +18,16 @@ fun test2() {
     X1.X2.x2++
     X1.X2.X3.x3++
 }
+
+class B(var s: Int = 0)
+
+object Host {
+    operator fun B.plusAssign(b: B) {
+        this.s += b.s
+    }
+}
+
+fun Host.test3(v: B) {
+    v += B(1000)
+}
+

compiler/testData/ir/irText/expressions/complexAugmentedAssignment.txt

@@ -86,3 +86,39 @@ FILE /complexAugmentedAssignment.kt
             <set-?>: CALL .inc type=kotlin.Int operator=POSTFIX_INCR
               $this: GET_VAR tmp5 type=kotlin.Int operator=null
           GET_VAR tmp5 type=kotlin.Int operator=null
+  CLASS CLASS B
+    CONSTRUCTOR public constructor B(/*0*/ s: kotlin.Int = ...)
+      s: EXPRESSION_BODY
+        CONST Int type=kotlin.Int value='0'
+      BLOCK_BODY
+        DELEGATING_CONSTRUCTOR_CALL Any
+        SET_BACKING_FIELD s type=kotlin.Unit operator=null
+          GET_VAR s type=kotlin.Int operator=INITIALIZE_PROPERTY_FROM_PARAMETER
+        INSTANCE_INITIALIZER_CALL classDescriptor=B
+    PROPERTY public final var s: kotlin.Int
+      EXPRESSION_BODY
+        GET_VAR s type=kotlin.Int operator=INITIALIZE_PROPERTY_FROM_PARAMETER
+  CLASS OBJECT Host
+    CONSTRUCTOR private constructor Host()
+      BLOCK_BODY
+        DELEGATING_CONSTRUCTOR_CALL Any
+        INSTANCE_INITIALIZER_CALL classDescriptor=Host
+    FUN public final operator fun B.plusAssign(/*0*/ b: B): kotlin.Unit
+      BLOCK_BODY
+        BLOCK type=kotlin.Unit operator=PLUSEQ
+          VAR val tmp0_this: B
+            $RECEIVER of: plusAssign type=B
+          CALL .<set-s> type=kotlin.Unit operator=PLUSEQ
+            $this: GET_VAR tmp0_this type=B operator=null
+            <set-?>: CALL .plus type=kotlin.Int operator=PLUSEQ
+              $this: CALL .<get-s> type=kotlin.Int operator=PLUSEQ
+                $this: GET_VAR tmp0_this type=B operator=null
+              other: CALL .<get-s> type=kotlin.Int operator=GET_PROPERTY
+                $this: GET_VAR b type=B operator=null
+  FUN public fun Host.test3(/*0*/ v: B): kotlin.Unit
+    BLOCK_BODY
+      CALL .plusAssign type=kotlin.Unit operator=PLUSEQ
+        $this: $RECEIVER of: test3 type=Host
+        $receiver: GET_VAR v type=B operator=PLUSEQ
+        b: CALL .<init> type=B operator=null
+          s: CONST Int type=kotlin.Int value='1000'