[cxx-interop] Add NewCxxMethodSafetyHeuristics feature and guard swift compiler sources changes on it.

Author: zoecarver

SwiftCompilerSources/Sources/Basic/SourceLoc.swift

@@ -27,7 +27,11 @@ public struct SourceLoc {
     guard bridged.isValid() else {
       return nil
     }
+#if hasFeature(NewCxxMethodSafetyHeuristics)
+    self.locationInFile = bridged.getOpaquePointerValue().assumingMemoryBound(to: UInt8.self)
+#else
     self.locationInFile = bridged.__getOpaquePointerValueUnsafe().assumingMemoryBound(to: UInt8.self)
+#endif
   }
 
   public var bridged: swift.SourceLoc {
@@ -57,9 +61,15 @@ public struct CharSourceRange {
   }
 
   public init?(bridged: swift.CharSourceRange) {
+#if hasFeature(NewCxxMethodSafetyHeuristics)
+    guard let start = SourceLoc(bridged: bridged.getStart()) else {
+      return nil
+    }
+#else
     guard let start = SourceLoc(bridged: bridged.__getStartUnsafe()) else {
       return nil
     }
+#endif
     self.init(start: start, byteLength: bridged.getByteLength())
   }
 

SwiftCompilerSources/Sources/Basic/Utils.swift

@@ -64,11 +64,34 @@ public struct StringRef : CustomStringConvertible, NoReflectionChildren {
 
   public var string: String { _bridged.string }
   public var description: String { string }
-  
+
+  public var count: Int {
+#if hasFeature(NewCxxMethodSafetyHeuristics)
+    Int(_bridged.bytes_end() - _bridged.bytes_begin())
+#else
+    Int(_bridged.__bytes_endUnsafe() - _bridged.__bytes_beginUnsafe())
+#endif
+  }
+
+  public subscript(index: Int) -> UInt8 {
+#if hasFeature(NewCxxMethodSafetyHeuristics)
+    let buffer = UnsafeBufferPointer<UInt8>(start: _bridged.bytes_begin(),
+                                            count: count)
+#else
+    let buffer = UnsafeBufferPointer<UInt8>(start: _bridged.bytes_begin(),
+                                            count: count)
+#endif
+    return buffer[index]
+  }
+
   public static func ==(lhs: StringRef, rhs: StaticString) -> Bool {
+#if hasFeature(NewCxxMethodSafetyHeuristics)
     let lhsBuffer = UnsafeBufferPointer<UInt8>(
-      start: lhs._bridged.__bytes_beginUnsafe(),
+      start: lhs._bridged.bytes_begin(),
+      count: lhs.count)
+#else
       count: Int(lhs._bridged.__bytes_endUnsafe() - lhs._bridged.__bytes_beginUnsafe()))
+#endif
     return rhs.withUTF8Buffer { (rhsBuffer: UnsafeBufferPointer<UInt8>) in
       if lhsBuffer.count != rhsBuffer.count { return false }
       return lhsBuffer.elementsEqual(rhsBuffer, by: ==)

include/swift/Basic/Features.def

@@ -197,6 +197,10 @@ EXPERIMENTAL_FEATURE(RuntimeDiscoverableAttrs, false)
 /// signatures.
 EXPERIMENTAL_FEATURE(ImportSymbolicCXXDecls, false)
 
+// Only import C++ methods that return pointers (projections) on owned types as
+// unsafe.
+EXPERIMENTAL_FEATURE(NewCxxMethodSafetyHeuristics, true)
+
 /// Generate bindings for functions that 'throw' in the C++ section of the generated Clang header.
 EXPERIMENTAL_FEATURE(GenerateBindingsForThrowingFunctionsInCXX, false)
 

lib/AST/ASTPrinter.cpp

@@ -3448,6 +3448,10 @@ static bool usesFeatureBuiltinModule(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureNewCxxMethodSafetyHeuristics(Decl *decl) {
+  return decl->hasClangNode();
+}
+
 /// Suppress the printing of a particular feature.
 static void suppressingFeature(PrintOptions &options, Feature feature,
                                llvm::function_ref<void()> action) {