[interop][SwiftToCxx] do not expose move-only Swift types

Swift's consume semantics are not yet supported in C++

Author: hyp

include/swift/AST/DiagnosticsSema.def

@@ -1696,6 +1696,8 @@ ERROR(expose_enum_case_tuple_to_cxx,none,
       "enum %0 can not yet be represented in C++ as one of its cases has multiple associated values", (ValueDecl *))
 ERROR(expose_protocol_to_cxx_unsupported,none,
       "protocol %0 can not yet be represented in C++", (ValueDecl *))
+ERROR(expose_move_only_to_cxx,none,
+      "move-only %0 %1 can not yet be represented in C++", (DescriptiveDeclKind, ValueDecl *))
 ERROR(unexposed_other_decl_in_cxx,none,
       "%0 %1 is not yet exposed to C++", (DescriptiveDeclKind, ValueDecl *))
 ERROR(unsupported_other_decl_in_cxx,none,

include/swift/AST/SwiftNameTranslation.h

@@ -78,6 +78,7 @@ enum RepresentationError {
   UnrepresentableEnumCaseType,
   UnrepresentableEnumCaseTuple,
   UnrepresentableProtocol,
+  UnrepresentableMoveOnly,
 };
 
 /// Constructs a diagnostic that describes the given C++ representation error.

lib/AST/SwiftNameTranslation.cpp

@@ -226,6 +226,9 @@ swift::cxx_translation::getDeclRepresentation(const ValueDecl *VD) {
   if (const auto *typeDecl = dyn_cast<NominalTypeDecl>(VD)) {
     if (isa<ProtocolDecl>(typeDecl))
       return {Unsupported, UnrepresentableProtocol};
+    // Swift's consume semantics are not yet supported in C++.
+    if (typeDecl->isMoveOnly())
+      return {Unsupported, UnrepresentableMoveOnly};
     if (typeDecl->isGeneric()) {
       if (isa<ClassDecl>(VD))
         return {Unsupported, UnrepresentableGeneric};
@@ -323,5 +326,8 @@ swift::cxx_translation::diagnoseRepresenationError(RepresentationError error,
     return Diagnostic(diag::expose_enum_case_tuple_to_cxx, vd);
   case UnrepresentableProtocol:
     return Diagnostic(diag::expose_protocol_to_cxx_unsupported, vd);
+  case UnrepresentableMoveOnly:
+    return Diagnostic(diag::expose_move_only_to_cxx, vd->getDescriptiveKind(),
+                      vd);
   }
 }

test/Interop/SwiftToCxx/unsupported/unsupported-types-in-cxx.swift

@@ -12,13 +12,27 @@ public func takesVoid(_ x: ()) {}
 
 // CHECK:     takeFloat
 
-protocol TestProtocol {}
+@_moveOnly
+public enum MoveOnlyEnum {
+    case a
+}
+
+// CHECK: class MoveOnlyEnum { } SWIFT_UNAVAILABLE_MSG("move-only enum 'MoveOnlyEnum' can not yet be represented in C++");
+
+@_moveOnly
+public struct MoveOnlyStruct {
+    let x: Int
+}
+
+// CHECK: class MoveOnlyStruct { } SWIFT_UNAVAILABLE_MSG("move-only struct 'MoveOnlyStruct' can not yet be represented in C++");
+
+public protocol TestProtocol {}
 
 // CHECK: class TestProtocol { } SWIFT_UNAVAILABLE_MSG("protocol 'TestProtocol' can not yet be represented in C++");
 
 // CHECK: // Unavailable in C++: Swift global function 'takesTuple(_:)'.
 // CHECK: // Unavailable in C++: Swift global function 'takesVoid(_:)'.
 
-typealias unsupportedTypeAlias = () -> (Float, Float)
+public typealias unsupportedTypeAlias = () -> (Float, Float)
 
 // CHECK: // Unavailable in C++: Swift type alias 'unsupportedTypeAlias'