diff --git a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/IrSlots.kt b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/IrSlots.kt
index eedfe9aa81d..c75d84d1c16 100644
--- a/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/IrSlots.kt
+++ b/compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/IrSlots.kt
@@ -16,28 +16,34 @@
 
 package org.jetbrains.kotlin.ir
 
+// Slots should be unique within children of particular node type.
+// Non-negative numbers are used for slots in indexed container elements, for example, value arguments in a call.
+// NB a node can potentially contain several "containers"; it's up to a node how to organize numbering in such case.
+// Negative numbers are used for "named" slots, for example, dispatch and extension receivers in a call.
+
 const val DETACHED_SLOT = Int.MIN_VALUE
+
 const val CHILD_EXPRESSION_SLOT = 0
 const val ARGUMENT0_SLOT = 0
 const val ARGUMENT1_SLOT = 1
+const val SETTER_ARGUMENT_INDEX = 0
+
 const val DISPATCH_RECEIVER_SLOT = -1
 const val EXTENSION_RECEIVER_SLOT = -2
-const val BACKING_FIELD_RECEIVER_SLOT = -1
-const val FUNCTION_BODY_SLOT = -1
-const val ANONYMOUS_INITIALIZER_BODY_SLOT = -1
-const val MODULE_SLOT = 0
-const val INITIALIZER_SLOT = 0
-const val IF_CONDITION_SLOT = 0
-const val IF_THEN_SLOT = 1
-const val IF_ELSE_SLOT = -1
-const val LOOP_BODY_SLOT = -1
-const val LOOP_CONDITION_SLOT = -2
-const val SETTER_ARGUMENT_INDEX = 0
-const val TRY_RESULT_SLOT = -1
-const val FINALLY_EXPRESSION_SLOT = -2
-const val NESTED_INITIALIZERS_SLOT = -1
-const val PROPERTY_GETTER_SLOT = -1
-const val PROPERTY_SETTER_SLOT = -2
-const val DELEGATE_SLOT = -3
-const val ENUM_ENTRY_CLASS_SLOT = -1
-const val ENUM_ENTRY_INITIALIZER_SLOT = -2
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+const val BACKING_FIELD_RECEIVER_SLOT = -3
+const val FUNCTION_BODY_SLOT = -4
+const val ANONYMOUS_INITIALIZER_BODY_SLOT = -5
+const val MODULE_SLOT = -6
+const val INITIALIZER_SLOT = -7
+const val IF_CONDITION_SLOT = -8
+const val IF_THEN_SLOT = -9
+const val IF_ELSE_SLOT = -10
+const val LOOP_BODY_SLOT = -11
+const val LOOP_CONDITION_SLOT = -12
+const val TRY_RESULT_SLOT = -13
+const val FINALLY_EXPRESSION_SLOT = -14
+const val PROPERTY_GETTER_SLOT = -15
+const val PROPERTY_SETTER_SLOT = -16
+const val DELEGATE_SLOT = -17
+const val ENUM_ENTRY_CLASS_SLOT = -18
+const val ENUM_ENTRY_INITIALIZER_SLOT = -19
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