Forbid @_borrowed in @abi

It has indirect effects on the accessors, so it shouldn’t matter, but we can defensively redirect the query to the API counterpart anyway.

This was the last `InferredInABIAttr` attribute, so we can now remove all of the infrastructure involved in supporting attribute inference.

Author: beccadax

include/swift/AST/Attr.h

@@ -380,21 +380,14 @@ class DeclAttribute : public AttributeBase {
     /// valid if they match. 
     EquivalentInABIAttr = 1ull << 18,
 
-    /// Attribute can be used in an \c \@abi attribute, but must match
-    /// equivalent on API decl; if omitted, API decl's attribute will be 
-    /// cloned. Use where you would want to use \c EquivalentInABIAttr but 
-    /// repeating the attribute is judged too burdensome.
-    InferredInABIAttr = 1ull << 19,
-
     /// Use for attributes which are \em only valid on declarations that cannot
     /// have an \c @abi attribute, such as \c ImportDecl .
-    UnreachableInABIAttr = 1ull << 20,
+    UnreachableInABIAttr = 1ull << 19,
   };
 
   enum : uint64_t {
     InABIAttrMask = ForbiddenInABIAttr | UnconstrainedInABIAttr
-                  | EquivalentInABIAttr | InferredInABIAttr
-                  | UnreachableInABIAttr
+                  | EquivalentInABIAttr | UnreachableInABIAttr
   };
 
   LLVM_READNONE

include/swift/AST/DeclAttr.def

@@ -456,7 +456,7 @@ DECL_ATTR(_dynamicReplacement, DynamicReplacement,
 
 SIMPLE_DECL_ATTR(_borrowed, Borrowed,
   OnVar | OnSubscript,
-  UserInaccessible | NotSerialized | ABIBreakingToAdd | ABIBreakingToRemove | APIStableToAdd | APIStableToRemove | InferredInABIAttr,
+  UserInaccessible | NotSerialized | ABIBreakingToAdd | ABIBreakingToRemove | APIStableToAdd | APIStableToRemove | ForbiddenInABIAttr,
   81)
 
 DECL_ATTR(_private, PrivateImport,

include/swift/AST/DiagnosticsSema.def

@@ -8467,9 +8467,6 @@ ERROR(attr_abi_extra_attr,none,
 ERROR(attr_abi_forbidden_attr,none,
       "unused '%0' %select{attribute|modifier}1 in '@abi'",
       (StringRef, bool))
-REMARK(abi_attr_inferred_attribute,none,
-       "inferred '%0' in '@abi' to match %select{attribute|modifier}1 on API",
-       (StringRef, bool))
 
 ERROR(attr_abi_mismatched_attr,none,
       "'%0' %select{attribute|modifier}1 in '@abi' should match '%2'",

include/swift/Basic/LangOptions.h

@@ -269,9 +269,6 @@ namespace swift {
     /// Emit a remark on early exit in explicit interface build
     bool EnableSkipExplicitInterfaceModuleBuildRemarks = false;
 
-    /// Emit a remark when \c \@abi infers an attribute or modifier.
-    bool EnableABIInferenceRemarks = false;
-
     ///
     /// Support for alternate usage modes
     ///

include/swift/Option/Options.td

@@ -468,10 +468,6 @@ def remark_module_serialization : Flag<["-"], "Rmodule-serialization">,
   Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
   HelpText<"Emit remarks about module serialization">;
 
-def remark_abi_inference : Flag<["-"], "Rabi-inference">,
-  Flags<[FrontendOption, DoesNotAffectIncrementalBuild]>,
-  HelpText<"Emit a remark when an '@abi' attribute adds an attribute or modifier to the ABI declaration based on its presence in the API">;
-
 def emit_tbd : Flag<["-"], "emit-tbd">,
   HelpText<"Emit a TBD file">,
   Flags<[FrontendOption, NoInteractiveOption, SupplementaryOutput]>;

lib/AST/Attr.cpp

@@ -61,7 +61,7 @@ static_assert(IsTriviallyDestructible<DeclAttributes>::value,
                 DeclAttribute::APIBreakingToRemove | DeclAttribute::APIStableToRemove), \
                 #Name " needs to specify either APIBreakingToRemove or APIStableToRemove"); \
   static_assert(DeclAttribute::hasOneBehaviorFor##Id(DeclAttribute::InABIAttrMask), \
-                #Name " needs to specify exactly one of ForbiddenInABIAttr, UnconstrainedInABIAttr, EquivalentInABIAttr, InferredInABIAttr, or UnreachableInABIAttr");
+                #Name " needs to specify exactly one of ForbiddenInABIAttr, UnconstrainedInABIAttr, EquivalentInABIAttr, or UnreachableInABIAttr");
 #include "swift/AST/DeclAttr.def"
 
 #define TYPE_ATTR(_, Id)                                                       \

lib/Frontend/CompilerInvocation.cpp

@@ -1422,8 +1422,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   Opts.EnableSkipExplicitInterfaceModuleBuildRemarks = Args.hasArg(OPT_remark_skip_explicit_interface_build);
 
-  Opts.EnableABIInferenceRemarks = Args.hasArg(OPT_remark_abi_inference);
-
   if (Args.hasArg(OPT_experimental_skip_non_exportable_decls)) {
     // Only allow -experimental-skip-non-exportable-decls if either library
     // evolution is enabled (in which case the module's ABI is independent of

lib/Sema/TypeCheckAttrABI.cpp

@@ -880,26 +880,6 @@ class ABIDeclChecker : public ASTComparisonVisitor<ABIDeclChecker> {
 
       return false;
 
-    case DeclAttribute::InferredInABIAttr:
-      if (!abi && api->canClone()) {
-        // Infer an identical attribute.
-        abi = api->clone(ctx);
-        abi->setImplicit(true);
-        abiDecl->getAttrs().add(abi);
-
-        if (ctx.LangOpts.EnableABIInferenceRemarks) {
-          SmallString<64> scratch;
-          auto abiAttrAsString = printAttr(abi, abiDecl, scratch);
-
-          abiDecl->diagnose(diag::abi_attr_inferred_attribute,
-                            abiAttrAsString, api->isDeclModifier());
-          noteAttrHere(api, apiDecl, /*isMatch=*/true);
-        }
-      }
-
-      // Other than the cloning behavior, Inferred behaves like Equivalent.
-      LLVM_FALLTHROUGH;
-
     case DeclAttribute::EquivalentInABIAttr:
       // Diagnose if API doesn't have attribute.
       if (!api) {

lib/Sema/TypeCheckStorage.cpp

@@ -849,6 +849,10 @@ IsSetterMutatingRequest::evaluate(Evaluator &evaluator,
 OpaqueReadOwnership
 OpaqueReadOwnershipRequest::evaluate(Evaluator &evaluator,
                                      AbstractStorageDecl *storage) const {
+  auto abiRole = ABIRoleInfo(storage);
+  if (!abiRole.providesAPI() && abiRole.getCounterpart())
+    return abiRole.getCounterpart()->getOpaqueReadOwnership();
+
   enum class DiagKind {
     BorrowedAttr,
     NoncopyableType

test/attr/attr_abi.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature Extern -enable-experimental-feature ABIAttribute -enable-experimental-feature AddressableParameters -enable-experimental-feature NoImplicitCopy -enable-experimental-feature SymbolLinkageMarkers -enable-experimental-feature StrictMemorySafety -enable-experimental-feature LifetimeDependence -enable-experimental-feature CImplementation -import-bridging-header %S/Inputs/attr_abi.h -parse-as-library -Rabi-inference -debugger-support
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature Extern -enable-experimental-feature ABIAttribute -enable-experimental-feature AddressableParameters -enable-experimental-feature NoImplicitCopy -enable-experimental-feature SymbolLinkageMarkers -enable-experimental-feature StrictMemorySafety -enable-experimental-feature LifetimeDependence -enable-experimental-feature CImplementation -import-bridging-header %S/Inputs/attr_abi.h -parse-as-library -debugger-support
 
 // REQUIRES: swift_feature_ABIAttribute
 // REQUIRES: swift_feature_AddressableParameters
@@ -2034,15 +2034,15 @@ extension DynamicReplacement {
 
 // @_weakLinked -- tested in attr/attr_weaklinked.swift
 
-// @_borrowed -- automatically cloned into @abi
+// @_borrowed -- banned in @abi
 protocol BorrowedAttr {
-  @abi(@_borrowed var v1: Int)
+  @abi(@_borrowed var v1: Int) // expected-error {{unused '_borrowed' attribute in '@abi'}} {{8-18=}}
   @_borrowed var v1: Int { get set }
 
-  @abi(var v2: Int) // expected-remark {{inferred '@_borrowed' in '@abi' to match attribute on API}}
-  @_borrowed var v2: Int { get set } // expected-note {{matches attribute here}}
+  @abi(var v2: Int)
+  @_borrowed var v2: Int { get set }
 
-  @abi(@_borrowed var v3: Int) // expected-error {{extra '_borrowed' attribute in '@abi'}} {{8-18=}}
+  @abi(@_borrowed var v3: Int) // expected-error {{unused '_borrowed' attribute in '@abi'}} {{8-18=}}
   var v3: Int { get set }
 }