Properly calculate safe call receivers

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

@@ -86,12 +86,9 @@ fun StatementGenerator.generateCallReceiver(
     return when {
         !isSafe ->
             SimpleCallReceiver(dispatchReceiverValue, extensionReceiverValue)
-        extensionReceiverValue != null ->
+        extensionReceiverValue != null  || dispatchReceiverValue != null->
             SafeCallReceiver(this, ktDefaultElement.startOffset, ktDefaultElement.endOffset,
-                             extensionReceiverValue.load(), dispatchReceiverValue, isAssignmentReceiver)
-        dispatchReceiverValue != null ->
-            SafeCallReceiver(this, ktDefaultElement.startOffset, ktDefaultElement.endOffset,
-                             dispatchReceiverValue.load(), null, isAssignmentReceiver)
+                             extensionReceiverValue, dispatchReceiverValue, isAssignmentReceiver)
         else ->
             throw AssertionError("Safe call should have an explicit receiver: ${ktDefaultElement.text}")
     }

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/intermediate/SafeCallReceiver.kt

@@ -31,18 +31,18 @@ class SafeCallReceiver(
         val generator: GeneratorWithScope,
         val startOffset: Int,
         val endOffset: Int,
-        val explicitReceiver: IrExpression,
-        val implicitDispatchReceiverValue: IntermediateValue?,
+        val extensionReceiver: IntermediateValue?,
+        val dispatchReceiver: IntermediateValue?,
         val isAssignmentReceiver: Boolean
 ) : CallReceiver {
     override fun call(withDispatchAndExtensionReceivers: (IntermediateValue?, IntermediateValue?) -> IrExpression): IrExpression {
-        val irTmp = generator.scope.createTemporaryVariable(explicitReceiver, "safe_receiver")
+        val irTmp = generator.scope.createTemporaryVariable(extensionReceiver?.load() ?: dispatchReceiver!!.load(), "safe_receiver")
         val safeReceiverValue = VariableLValue(irTmp)
 
-        val dispatchReceiverValue: IntermediateValue
+        val dispatchReceiverValue: IntermediateValue?
         val extensionReceiverValue: IntermediateValue?
-        if (implicitDispatchReceiverValue != null) {
-            dispatchReceiverValue = implicitDispatchReceiverValue
+        if (extensionReceiver != null) {
+            dispatchReceiverValue = dispatchReceiver
             extensionReceiverValue = safeReceiverValue
         }
         else {