IJ file type optimizations based on extension

#KTIJ-21668

Merge-request: KT-MR-6288
Merged-by: Vladimir Dolzhenko <Vladimir.Dolzhenko@jetbrains.com>

analysis/decompiled/decompiler-to-file-stubs/src/org/jetbrains/kotlin/analysis/decompiler/stub/file/KotlinMetadataStubBuilder.kt

@@ -33,7 +33,7 @@ open class KotlinMetadataStubBuilder(
 
     override fun buildFileStub(content: FileContent): PsiFileStub<*>? {
         val virtualFile = content.file
-        assert(virtualFile.fileType == fileType) { "Unexpected file type ${virtualFile.fileType}" }
+        assert(virtualFile.extension == fileType.defaultExtension || virtualFile.fileType == fileType) { "Unexpected file type ${virtualFile.fileType.name}" }
         val file = readFile(virtualFile, content.content) ?: return null
 
         when (file) {

analysis/decompiled/decompiler-to-psi/src/org/jetbrains/kotlin/analysis/decompiler/psi/KotlinMetadataDecompiler.kt

@@ -40,7 +40,7 @@ abstract class KotlinMetadataDecompiler<out V : BinaryVersion>(
 
     abstract fun readFile(bytes: ByteArray, file: VirtualFile): KotlinMetadataStubBuilder.FileWithMetadata?
 
-    override fun accepts(file: VirtualFile) = file.fileType == fileType
+    override fun accepts(file: VirtualFile) = file.extension == fileType.defaultExtension || file.fileType == fileType
 
     override fun getStubBuilder() = metadataStubBuilder
 

analysis/decompiled/light-classes-for-decompiled/src/org/jetbrains/kotlin/analysis/decompiled/light/classes/ClsJavaStubByVirtualFileCache.kt

@@ -33,7 +33,7 @@ class ClsJavaStubByVirtualFileCache {
     }
 
     private fun createStub(file: VirtualFile): PsiJavaFileStub? {
-        if (file.fileType !== JavaClassFileType.INSTANCE) return null
+        if (file.extension != JavaClassFileType.INSTANCE.defaultExtension && file.fileType !== JavaClassFileType.INSTANCE) return null
 
         try {
             return ClsFileImpl.buildFileStub(file, file.contentsToByteArray(false))