Support common metadata in kotlinx-metadata

KotlinCommonMetadata can be used to inspect .kotlin_builtins and
.kotlin_metadata files. It's in an internal package for now, but might
be published once the API is finalized.

core/deserialization/src/org/jetbrains/kotlin/serialization/deserialization/builtins/BuiltInsPackageFragmentImpl.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.builtins.BuiltInsPackageFragment
 import org.jetbrains.kotlin.descriptors.ModuleDescriptor
 import org.jetbrains.kotlin.metadata.ProtoBuf
 import org.jetbrains.kotlin.metadata.builtins.BuiltInsBinaryVersion
+import org.jetbrains.kotlin.metadata.builtins.readBuiltinsPackageFragment
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.serialization.deserialization.DeserializedPackageFragmentImpl
@@ -33,21 +34,15 @@ class BuiltInsPackageFragmentImpl private constructor(
             inputStream: InputStream,
             isFallback: Boolean
         ): BuiltInsPackageFragmentImpl {
-            lateinit var version: BuiltInsBinaryVersion
+            val (proto, version) = inputStream.readBuiltinsPackageFragment()
 
-            val proto = inputStream.use { stream ->
-                version = BuiltInsBinaryVersion.readFrom(stream)
-
-                if (!version.isCompatible()) {
-                    // TODO: report a proper diagnostic
-                    throw UnsupportedOperationException(
-                        "Kotlin built-in definition format version is not supported: " +
-                                "expected ${BuiltInsBinaryVersion.INSTANCE}, actual $version. " +
-                                "Please update Kotlin"
-                    )
-                }
-
-                ProtoBuf.PackageFragment.parseFrom(stream, BuiltInSerializerProtocol.extensionRegistry)
+            if (proto == null) {
+                // TODO: report a proper diagnostic
+                throw UnsupportedOperationException(
+                    "Kotlin built-in definition format version is not supported: " +
+                            "expected ${BuiltInsBinaryVersion.INSTANCE}, actual $version. " +
+                            "Please update Kotlin"
+                )
             }
 
             return BuiltInsPackageFragmentImpl(fqName, storageManager, module, proto, version, isFallback)

core/metadata/src/org/jetbrains/kotlin/metadata/builtins/readPackageFragment.kt

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.metadata.builtins
+
+import org.jetbrains.kotlin.metadata.ProtoBuf
+import org.jetbrains.kotlin.protobuf.ExtensionRegistryLite
+import java.io.InputStream
+
+fun InputStream.readBuiltinsPackageFragment(): Pair<ProtoBuf.PackageFragment?, BuiltInsBinaryVersion> =
+    use { stream ->
+        val version = BuiltInsBinaryVersion.readFrom(stream)
+        val proto =
+            if (version.isCompatible()) ProtoBuf.PackageFragment.parseFrom(
+                stream,
+                ExtensionRegistryLite.newInstance().apply(BuiltInsProtoBuf::registerAllExtensions)
+            )
+            else null
+        proto to version
+    }