diff --git a/include/swift/AST/CASTBridging.h b/include/swift/AST/CASTBridging.h
index d068c26b928ad..2d6a5a7409113 100644
--- a/include/swift/AST/CASTBridging.h
+++ b/include/swift/AST/CASTBridging.h
@@ -247,6 +247,9 @@ void Diagnostic_finish(BridgedDiagnostic cDiag);
 BridgedIdentifier ASTContext_getIdentifier(BridgedASTContext cContext,
                                            BridgedString cStr);
 
+_Bool ASTContext_langOptsHasFeature(BridgedASTContext cContext,
+                                    BridgedFeature feature);
+
 void *ImportDecl_create(BridgedASTContext cContext,
                         BridgedDeclContext cDeclContext,
                         BridgedSourceLoc cImportLoc, char kind,
diff --git a/include/swift/Basic/CBasicBridging.h b/include/swift/Basic/CBasicBridging.h
index 0425b6b67c33b..1a99b83c703c2 100644
--- a/include/swift/Basic/CBasicBridging.h
+++ b/include/swift/Basic/CBasicBridging.h
@@ -22,7 +22,6 @@
 // layering. i.e. Darwin overlay is created by Swift compiler.
 
 SWIFT_BEGIN_NULLABILITY_ANNOTATIONS
-SWIFT_BEGIN_ASSUME_NONNULL
 
 #ifdef __cplusplus
 extern "C" {
@@ -31,6 +30,14 @@ extern "C" {
 
 #endif
 
+typedef enum ENUM_EXTENSIBILITY_ATTR(open) BridgedFeature {
+#define LANGUAGE_FEATURE(FeatureName, SENumber, Description, Option) \
+FeatureName,
+#include "swift/Basic/Features.def"
+} BridgedFeature;
+
+SWIFT_BEGIN_ASSUME_NONNULL
+
 typedef struct BridgedData {
   const char *_Nullable baseAddress;
   unsigned long size;
diff --git a/lib/AST/CASTBridging.cpp b/lib/AST/CASTBridging.cpp
index 50215828c43bf..e629b4057b0e9 100644
--- a/lib/AST/CASTBridging.cpp
+++ b/lib/AST/CASTBridging.cpp
@@ -176,6 +176,11 @@ BridgedIdentifier ASTContext_getIdentifier(BridgedASTContext cContext,
   return {convertASTContext(cContext).getIdentifier(str).getAsOpaquePointer()};
 }
 
+bool ASTContext_langOptsHasFeature(BridgedASTContext cContext,
+                                   BridgedFeature feature) {
+  return convertASTContext(cContext).LangOpts.hasFeature((Feature)feature);
+}
+
 void *ImportDecl_create(BridgedASTContext cContext,
                         BridgedDeclContext cDeclContext,
                         BridgedSourceLoc cImportLoc, char kind,
diff --git a/lib/ASTGen/Sources/ASTGen/ASTGen.swift b/lib/ASTGen/Sources/ASTGen/ASTGen.swift
index 5cfedde85a4d6..7d726f002b081 100644
--- a/lib/ASTGen/Sources/ASTGen/ASTGen.swift
+++ b/lib/ASTGen/Sources/ASTGen/ASTGen.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension Array {
diff --git a/lib/ASTGen/Sources/ASTGen/Decls.swift b/lib/ASTGen/Sources/ASTGen/Decls.swift
index 18241bac0711b..8f882925dae61 100644
--- a/lib/ASTGen/Sources/ASTGen/Decls.swift
+++ b/lib/ASTGen/Sources/ASTGen/Decls.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension ASTGenVisitor {
diff --git a/lib/ASTGen/Sources/ASTGen/Exprs.swift b/lib/ASTGen/Sources/ASTGen/Exprs.swift
index 636c9ee6d3d78..4b909ac3a32c3 100644
--- a/lib/ASTGen/Sources/ASTGen/Exprs.swift
+++ b/lib/ASTGen/Sources/ASTGen/Exprs.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension ASTGenVisitor {
diff --git a/lib/ASTGen/Sources/ASTGen/Generics.swift b/lib/ASTGen/Sources/ASTGen/Generics.swift
index 6893f184d59c2..cba550688b75e 100644
--- a/lib/ASTGen/Sources/ASTGen/Generics.swift
+++ b/lib/ASTGen/Sources/ASTGen/Generics.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension ASTGenVisitor {
diff --git a/lib/ASTGen/Sources/ASTGen/Macros.swift b/lib/ASTGen/Sources/ASTGen/Macros.swift
index 1c0df4f427261..96205f1d149e9 100644
--- a/lib/ASTGen/Sources/ASTGen/Macros.swift
+++ b/lib/ASTGen/Sources/ASTGen/Macros.swift
@@ -14,12 +14,15 @@ import CASTBridging
 import SwiftDiagnostics
 import SwiftOperators
 import SwiftParser
-import SwiftSyntax
 import SwiftSyntaxBuilder
 import SwiftSyntaxMacros
 import SwiftSyntaxMacroExpansion
 import SwiftCompilerPluginMessageHandling
 
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
+import SwiftSyntax
+
 extension SyntaxProtocol {
   func token(at position: AbsolutePosition) -> TokenSyntax? {
     // If the position isn't within this node at all, return early.
diff --git a/lib/ASTGen/Sources/ASTGen/Misc.swift b/lib/ASTGen/Sources/ASTGen/Misc.swift
index 9ccb04c0703c1..acc15c8b8bca5 100644
--- a/lib/ASTGen/Sources/ASTGen/Misc.swift
+++ b/lib/ASTGen/Sources/ASTGen/Misc.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension ASTGenVisitor {
diff --git a/lib/ASTGen/Sources/ASTGen/SourceFile.swift b/lib/ASTGen/Sources/ASTGen/SourceFile.swift
index 227f00e83e75c..5fc97b01503ca 100644
--- a/lib/ASTGen/Sources/ASTGen/SourceFile.swift
+++ b/lib/ASTGen/Sources/ASTGen/SourceFile.swift
@@ -1,8 +1,13 @@
+import CBasicBridging
+import CASTBridging
+
 import SwiftDiagnostics
-import SwiftParser
 import SwiftSyntax
 import SwiftParserDiagnostics
 
+@_spi(ExperimentalLanguageFeatures)
+import SwiftParser
+
 /// Describes a source file that has been "exported" to the C++ part of the
 /// compiler, with enough information to interface with the C++ layer.
 struct ExportedSourceFile {
@@ -20,15 +25,31 @@ struct ExportedSourceFile {
   let syntax: SourceFileSyntax
 }
 
+extension Parser.ExperimentalFeatures {
+  init(from context: BridgedASTContext?) {
+    self = []
+    guard let context = context else { return }
+
+    func mapFeature(_ bridged: BridgedFeature, to feature: Self) {
+      if ASTContext_langOptsHasFeature(context, bridged) {
+        insert(feature)
+      }
+    }
+  }
+}
+
 /// Parses the given source file and produces a pointer to a new
 /// ExportedSourceFile instance.
 @_cdecl("swift_ASTGen_parseSourceFile")
 public func parseSourceFile(
   buffer: UnsafePointer<UInt8>, bufferLength: Int,
-  moduleName: UnsafePointer<UInt8>, filename: UnsafePointer<UInt8>
+  moduleName: UnsafePointer<UInt8>, filename: UnsafePointer<UInt8>,
+  ctxPtr: UnsafeMutableRawPointer?
 ) -> UnsafeRawPointer {
   let buffer = UnsafeBufferPointer(start: buffer, count: bufferLength)
-  let sourceFile = Parser.parse(source: buffer)
+
+  let ctx = ctxPtr.map { BridgedASTContext(raw: $0) }
+  let sourceFile = Parser.parse(source: buffer, experimentalFeatures: .init(from: ctx))
 
   let exportedPtr = UnsafeMutablePointer<ExportedSourceFile>.allocate(capacity: 1)
   exportedPtr.initialize(
diff --git a/lib/ASTGen/Sources/ASTGen/Stmts.swift b/lib/ASTGen/Sources/ASTGen/Stmts.swift
index 5b32bd6611270..5a78ebcf5978a 100644
--- a/lib/ASTGen/Sources/ASTGen/Stmts.swift
+++ b/lib/ASTGen/Sources/ASTGen/Stmts.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension ASTGenVisitor {
diff --git a/lib/ASTGen/Sources/ASTGen/Types.swift b/lib/ASTGen/Sources/ASTGen/Types.swift
index 6d8dd8aeb304b..df0c9fef326dc 100644
--- a/lib/ASTGen/Sources/ASTGen/Types.swift
+++ b/lib/ASTGen/Sources/ASTGen/Types.swift
@@ -1,5 +1,8 @@
 import CASTBridging
 import SwiftParser
+
+// Needed to use SyntaxTransformVisitor's visit method.
+@_spi(SyntaxTransformVisitor)
 import SwiftSyntax
 
 extension ASTGenVisitor {
diff --git a/lib/Frontend/PrintingDiagnosticConsumer.cpp b/lib/Frontend/PrintingDiagnosticConsumer.cpp
index 36a1f47421326..828fdcce4d7e7 100644
--- a/lib/Frontend/PrintingDiagnosticConsumer.cpp
+++ b/lib/Frontend/PrintingDiagnosticConsumer.cpp
@@ -60,7 +60,8 @@ extern "C" void swift_ASTGen_renderQueuedDiagnostics(
 extern "C" void *swift_ASTGen_parseSourceFile(const char *buffer,
                                               size_t bufferLength,
                                               const char *moduleName,
-                                              const char *filename);
+                                              const char *filename,
+                                              void *_Nullable ctx);
 extern "C" void swift_ASTGen_destroySourceFile(void *sourceFile);
 
 namespace {
@@ -1047,7 +1048,7 @@ void PrintingDiagnosticConsumer::queueBuffer(
   auto bufferContents = sourceMgr.getEntireTextForBuffer(bufferID);
   auto sourceFile = swift_ASTGen_parseSourceFile(
       bufferContents.data(), bufferContents.size(),
-      "module", "file.swift");
+      "module", "file.swift", /*ctx*/ nullptr);
 
   // Find the parent and position in parent, if there is one.
   int parentID = -1;
diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 6a30f5c6a3b73..fcdef55ad6032 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -16,6 +16,7 @@
 
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/Attr.h"
+#include "swift/AST/CASTBridging.h"
 #include "swift/AST/DebuggerClient.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/DiagnosticsParse.h"
@@ -175,7 +176,8 @@ static void appendToVector(void *declPtr, void *vecPtr) {
 extern "C" void *swift_ASTGen_parseSourceFile(const char *buffer,
                                               size_t bufferLength,
                                               const char *moduleName,
-                                              const char *filename);
+                                              const char *filename,
+                                              void *_Nullable ctx);
 
 /// Destroy a source file parsed with swift_ASTGen_parseSourceFile.
 extern "C" void swift_ASTGen_destroySourceFile(void *sourceFile);
@@ -328,7 +330,7 @@ void *ExportedSourceFileRequest::evaluate(Evaluator &evaluator,
   auto exportedSourceFile = swift_ASTGen_parseSourceFile(
       contents.begin(), contents.size(),
       SF->getParentModule()->getName().str().str().c_str(),
-      SF->getFilename().str().c_str());
+      SF->getFilename().str().c_str(), &ctx);
 
   ctx.addCleanup([exportedSourceFile] {
     swift_ASTGen_destroySourceFile(exportedSourceFile);