diff --git a/json/src/com/jetbrains/jsonSchema/impl/JsonSchemaFileValuesIndex.java b/json/src/com/jetbrains/jsonSchema/impl/JsonSchemaFileValuesIndex.java
index 28c191c213a4..7a81586b454f 100644
--- a/json/src/com/jetbrains/jsonSchema/impl/JsonSchemaFileValuesIndex.java
+++ b/json/src/com/jetbrains/jsonSchema/impl/JsonSchemaFileValuesIndex.java
@@ -24,7 +24,7 @@ import org.jetbrains.annotations.Nullable;
 import java.util.HashMap;
 import java.util.Map;
 
-import static com.intellij.util.indexing.hints.BaseFileTypeInputFilter.FileTypeStrategy.BEFORE_SUBSTITUTION;
+import static com.intellij.util.indexing.hints.FileTypeSubstitutionStrategy.BEFORE_SUBSTITUTION;
 
 public class JsonSchemaFileValuesIndex extends FileBasedIndexExtension<String, String> {
   public static final ID<String, String> INDEX_ID = ID.create("json.file.root.values");
diff --git a/platform/indexing-impl/src/com/intellij/util/indexing/hints/BaseFileTypeInputFilter.kt b/platform/indexing-impl/src/com/intellij/util/indexing/hints/BaseFileTypeInputFilter.kt
index 4f653f7254f9..72681b9a1e78 100644
--- a/platform/indexing-impl/src/com/intellij/util/indexing/hints/BaseFileTypeInputFilter.kt
+++ b/platform/indexing-impl/src/com/intellij/util/indexing/hints/BaseFileTypeInputFilter.kt
@@ -6,7 +6,6 @@ import com.intellij.util.ThreeState
 import com.intellij.util.indexing.FileBasedIndex
 import com.intellij.util.indexing.IndexedFile
 import com.intellij.util.indexing.SubstitutedFileType
-import com.intellij.util.indexing.hints.BaseFileTypeInputFilter.FileTypeStrategy
 import org.jetbrains.annotations.ApiStatus
 
 /**
@@ -16,21 +15,20 @@ import org.jetbrains.annotations.ApiStatus
  *
  * If filetype is a [SubstitutedFileType] there are two options how to invoke [acceptFileType]: with filetype before substitution as
  * an argument ([SubstitutedFileType.getOriginalFileType]), or filetype after substitution ([SubstitutedFileType.getFileType]).
- * Default behavior is to use filetype after substitution. This can be changed via [FileTypeStrategy]
+ * Default behavior is to use filetype after substitution. This can be changed via [FileTypeSubstitutionStrategy]
  *
  * @see com.intellij.psi.LanguageSubstitutor
  */
 @ApiStatus.Experimental
-abstract class BaseFileTypeInputFilter(private val fileTypeStrategy: FileTypeStrategy) : FileBasedIndex.ProjectSpecificInputFilter,
-                                                                                         FileTypeIndexingHint {
-  enum class FileTypeStrategy { BEFORE_SUBSTITUTION, AFTER_SUBSTITUTION }
+abstract class BaseFileTypeInputFilter(private val fileTypeStrategy: FileTypeSubstitutionStrategy) : FileBasedIndex.ProjectSpecificInputFilter,
+                                                                                                     FileTypeIndexingHint {
 
-  constructor() : this(FileTypeStrategy.AFTER_SUBSTITUTION)
+  constructor() : this(FileTypeSubstitutionStrategy.AFTER_SUBSTITUTION)
 
   final override fun hintAcceptFileType(fileType: FileType): ThreeState {
     val fileTypeToUse: FileType =
       if (fileType is SubstitutedFileType) {
-        if (fileTypeStrategy == FileTypeStrategy.BEFORE_SUBSTITUTION) fileType.originalFileType else fileType.fileType
+        if (fileTypeStrategy == FileTypeSubstitutionStrategy.BEFORE_SUBSTITUTION) fileType.originalFileType else fileType.fileType
       }
       else {
         fileType
diff --git a/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeInputFilterPredicate.kt b/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeInputFilterPredicate.kt
index bab8dc73b2a5..cc9c8beb44bc 100644
--- a/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeInputFilterPredicate.kt
+++ b/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeInputFilterPredicate.kt
@@ -18,7 +18,7 @@ class FileTypeInputFilterPredicate : BaseFileTypeInputFilter {
     this.predicate = predicate
   }
 
-  constructor(fileTypeStrategy: FileTypeStrategy, predicate: (filetype: FileType) -> Boolean) : super(fileTypeStrategy) {
+  constructor(fileTypeStrategy: FileTypeSubstitutionStrategy, predicate: (filetype: FileType) -> Boolean) : super(fileTypeStrategy) {
     this.predicate = predicate
   }
 
diff --git a/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeSubstitutionStrategy.kt b/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeSubstitutionStrategy.kt
new file mode 100644
index 000000000000..bee4e2f16064
--- /dev/null
+++ b/platform/indexing-impl/src/com/intellij/util/indexing/hints/FileTypeSubstitutionStrategy.kt
@@ -0,0 +1,17 @@
+// Copyright 2000-2023 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+package com.intellij.util.indexing.hints
+
+import com.intellij.util.indexing.SubstitutedFileType
+
+/**
+ * [SubstitutedFileType] is an error-prone way to use filetype. Effectively it means that some file has two file types:
+ * before substitution ([SubstitutedFileType.getOriginalFileType]) and after substitution ([SubstitutedFileType.getFileType]).
+ *
+ * Client code often does not expect that it needs to deal with some artificial [SubstitutedFileType] that is not equal to
+ * any real filetype (e.g. JavaFileType). To simplify API, some classes (e.g. [BaseFileTypeInputFilter]) resolve
+ * [SubstitutedFileType] to real filetype. [FileTypeSubstitutionStrategy] defines the resolution strategy.
+ */
+enum class FileTypeSubstitutionStrategy {
+  BEFORE_SUBSTITUTION,
+  AFTER_SUBSTITUTION
+}
\ No newline at end of file
diff --git a/plugins/htmltools/src/com/intellij/htmltools/html/HtmlTagIdIndex.java b/plugins/htmltools/src/com/intellij/htmltools/html/HtmlTagIdIndex.java
index 0520dda5e1ec..055c532afb97 100644
--- a/plugins/htmltools/src/com/intellij/htmltools/html/HtmlTagIdIndex.java
+++ b/plugins/htmltools/src/com/intellij/htmltools/html/HtmlTagIdIndex.java
@@ -24,7 +24,7 @@ import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 
-import static com.intellij.util.indexing.hints.BaseFileTypeInputFilter.FileTypeStrategy.BEFORE_SUBSTITUTION;
+import static com.intellij.util.indexing.hints.FileTypeSubstitutionStrategy.BEFORE_SUBSTITUTION;
 
 public class HtmlTagIdIndex extends XmlIndex<Integer> {
   public static final ID<String, Integer> INDEX = ID.create("HtmlTagIdIndex");
diff --git a/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PyModuleNameIndex.java b/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PyModuleNameIndex.java
index 04b92b76a990..5b522e50d35d 100644
--- a/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PyModuleNameIndex.java
+++ b/python/python-psi-impl/src/com/jetbrains/python/psi/stubs/PyModuleNameIndex.java
@@ -23,7 +23,7 @@ import org.jetbrains.annotations.NotNull;
 
 import java.util.*;
 
-import static com.intellij.util.indexing.hints.BaseFileTypeInputFilter.FileTypeStrategy.BEFORE_SUBSTITUTION;
+import static com.intellij.util.indexing.hints.FileTypeSubstitutionStrategy.BEFORE_SUBSTITUTION;
 
 public class PyModuleNameIndex extends ScalarIndexExtension<String> {
   public static final ID<String, Void> NAME = ID.create("Py.module.name");