Adopt experimental-feature infrastructure for move-only feature

Author: DougGregor

include/swift/Basic/Features.def

@@ -87,6 +87,7 @@ EXPERIMENTAL_FEATURE(StaticAssert)
 EXPERIMENTAL_FEATURE(VariadicGenerics)
 EXPERIMENTAL_FEATURE(NamedOpaqueTypes)
 EXPERIMENTAL_FEATURE(FlowSensitiveConcurrencyCaptures)
+EXPERIMENTAL_FEATURE(MoveOnly)
 
 #undef EXPERIMENTAL_FEATURE
 #undef SUPPRESSIBLE_LANGUAGE_FEATURE

include/swift/Basic/LangOptions.h

@@ -330,9 +330,6 @@ namespace swift {
     /// Enable inference of Sendable conformances for public types.
     bool EnableInferPublicSendable = false;
 
-    /// Enable experimental 'move only' features.
-    bool EnableExperimentalMoveOnly = false;
-
     /// Enable experimental associated type inference using type witness
     /// systems.
     bool EnableExperimentalAssociatedTypeInference = false;

lib/AST/ASTPrinter.cpp

@@ -3011,6 +3011,10 @@ static bool usesFeatureFlowSensitiveConcurrencyCaptures(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureMoveOnly(Decl *decl) {
+  return false;
+}
+
 static void
 suppressingFeatureNoAsyncAvailability(PrintOptions &options,
                                       llvm::function_ref<void()> action) {

lib/Frontend/CompilerInvocation.cpp

@@ -458,9 +458,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.EnableExperimentalAssociatedTypeInference |=
       Args.hasArg(OPT_enable_experimental_associated_type_inference);
 
-  Opts.EnableExperimentalMoveOnly |=
-    Args.hasArg(OPT_enable_experimental_move_only);
-
   Opts.EnableInferPublicSendable |=
     Args.hasFlag(OPT_enable_infer_public_concurrent_value,
                  OPT_disable_infer_public_concurrent_value,
@@ -662,6 +659,8 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     Opts.Features.insert(Feature::NamedOpaqueTypes);
   if (Args.hasArg(OPT_enable_experimental_flow_sensitive_concurrent_captures))
     Opts.Features.insert(Feature::FlowSensitiveConcurrencyCaptures);
+  if (Args.hasArg(OPT_enable_experimental_move_only))
+    Opts.Features.insert(Feature::MoveOnly);
 
   Opts.EnableAppExtensionRestrictions |= Args.hasArg(OPT_enable_app_extension);
 

lib/SILGen/SILGenDecl.cpp

@@ -474,7 +474,7 @@ class LetValueInitialization : public Initialization {
 
     // Make sure that we have a non-address only type when binding a
     // @_noImplicitCopy let.
-    if (SGF.getASTContext().LangOpts.EnableExperimentalMoveOnly &&
+    if (SGF.getASTContext().LangOpts.hasFeature(Feature::MoveOnly) &&
         lowering.isAddressOnly() &&
         vd->getAttrs().hasAttribute<NoImplicitCopyAttr>()) {
       auto d = diag::noimplicitcopy_used_on_generic_or_existential;
@@ -556,7 +556,7 @@ class LetValueInitialization : public Initialization {
 
     if (SGF.getASTContext().SILOpts.supportsLexicalLifetimes(SGF.getModule()) &&
         value->getOwnershipKind() != OwnershipKind::None) {
-      if (!SGF.getASTContext().LangOpts.EnableExperimentalMoveOnly) {
+      if (!SGF.getASTContext().LangOpts.hasFeature(Feature::MoveOnly)) {
         value = SILValue(
             SGF.B.createBeginBorrow(PrologueLoc, value, /*isLexical*/ true));
       } else {
@@ -1801,7 +1801,7 @@ void SILGenFunction::destroyLocalVariable(SILLocation silLoc, VarDecl *vd) {
     return;
   }
 
-  if (getASTContext().LangOpts.EnableExperimentalMoveOnly) {
+  if (getASTContext().LangOpts.hasFeature(Feature::MoveOnly)) {
     if (auto *mvi = dyn_cast<MarkMustCheckInst>(Val.getDefiningInstruction())) {
       if (mvi->isNoImplicitCopy()) {
         if (auto *cvi = dyn_cast<CopyValueInst>(mvi->getOperand())) {

lib/Sema/TypeCheckAttr.cpp

@@ -328,7 +328,7 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
 void AttributeChecker::visitNoImplicitCopyAttr(NoImplicitCopyAttr *attr) {
   // Only allow for this attribute to be used when experimental move only is
   // enabled.
-  if (!D->getASTContext().LangOpts.EnableExperimentalMoveOnly) {
+  if (!D->getASTContext().LangOpts.hasFeature(Feature::MoveOnly)) {
     auto error =
         diag::experimental_moveonly_feature_can_only_be_used_when_enabled;
     diagnoseAndRemoveAttr(attr, error);

tools/sil-opt/SILOpt.cpp

@@ -561,9 +561,8 @@ int main(int argc, char **argv) {
     EnableExperimentalConcurrency;
   Optional<bool> enableExperimentalMoveOnly =
       toOptionalBool(EnableExperimentalMoveOnly);
-  if (enableExperimentalMoveOnly)
-    Invocation.getLangOptions().EnableExperimentalMoveOnly =
-        *enableExperimentalMoveOnly;
+  if (enableExperimentalMoveOnly && *enableExperimentalMoveOnly)
+    Invocation.getLangOptions().Features.insert(Feature::MoveOnly);
 
   Invocation.getLangOptions().EnableObjCInterop =
     EnableObjCInterop ? true :