Merge pull request #41612 from tshortli/back-deploy-diagnose-decls

Update @_backDeploy ABI semantics and diagnose invalid declarations

Author: tshortli

include/swift/AST/Attr.def

@@ -718,7 +718,7 @@ DECL_ATTR(exclusivity, Exclusivity,
   128)
 
 DECL_ATTR(_backDeploy, BackDeploy,
-  OnAbstractFunction |
+  OnAbstractFunction | OnAccessor | OnSubscript | OnVar |
   AllowMultipleAttributes | LongAttribute | UserInaccessible |
   ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIBreakingToRemove,
   129)

include/swift/AST/Decl.h

@@ -825,6 +825,11 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   /// This function won't consider the parent context to get the information.
   Optional<llvm::VersionTuple> getIntroducedOSVersion(PlatformKind Kind) const;
 
+  /// Returns the OS version in which the decl became ABI as specified by the
+  /// @_backDeploy attribute.
+  Optional<llvm::VersionTuple>
+  getBackDeployBeforeOSVersion(PlatformKind Kind) const;
+
   /// Returns the starting location of the entire declaration.
   SourceLoc getStartLoc() const { return getSourceRange().Start; }
 

include/swift/AST/DiagnosticsSema.def

@@ -1599,26 +1599,12 @@ WARNING(option_set_zero_constant,none,
 NOTE(option_set_empty_set_init,none,
      "use [] to silence this warning", ())
 
-// FIXME(backDeploy): Refactor to share with back deployment attr
-ERROR(originally_defined_in_dupe_platform,none,
-      "duplicate version number for platform %0", (StringRef))
-
 ERROR(originally_definedin_topleve_decl,none,
       "@%0 is only applicable to top-level decl", (StringRef))
 
-// FIXME(backDeploy): Refactor to share with back deployment attr
-ERROR(originally_definedin_need_available,none,
-      "need @available attribute for @%0", (StringRef))
-
 ERROR(originally_definedin_must_not_before_available_version,none,
       "symbols are moved to the current module before they were available in the OSs", (StringRef))
 
-// FIXME(backDeploy): Refactor to share with back deployment attr
-WARNING(originally_defined_in_on_non_public,
-       none, "@%0 does not have any effect on "
-       "%select{private|fileprivate|internal|%error|%error}1 declarations",
-       (StringRef, AccessLevel))
-
 // Alignment attribute
 ERROR(alignment_not_power_of_two,none,
       "alignment value must be a power of two", ())
@@ -3139,10 +3125,28 @@ ERROR(attr_not_on_variadic_parameters,none,
       "'%0' must not be used on variadic parameters", (StringRef))
 ERROR(attr_not_on_subscript_parameters,none,
       "'%0' must not be used on subscript parameters", (StringRef))
+ERROR(attr_not_on_stored_properties,none,
+      "'%0' must not be used on stored properties", (DeclAttribute))
+
+WARNING(attr_has_no_effect_on_decl_with_access_level,none,
+       "'%0' does not have any effect on "
+       "%select{private|fileprivate|internal|%error|%error}1 declarations",
+       (DeclAttribute, AccessLevel))
+ERROR(attr_not_on_decl_with_invalid_access_level,none,
+      "'%0' may not be used on "
+      "%select{private|fileprivate|internal|%error|%error}1 declarations",
+      (DeclAttribute, AccessLevel))
+
+ERROR(attr_has_no_effect_decl_not_available_before,none,
+      "'%0' has no effect because %1 is not available before %2 %3",
+      (DeclAttribute, DeclName, StringRef, llvm::VersionTuple))
 
 ERROR(attr_ambiguous_reference_to_decl,none,
       "ambiguous reference to %0 in '@%1' attribute", (DeclNameRef, StringRef))
 
+ERROR(attr_contains_multiple_versions_for_platform,none,
+      "'%0' contains multiple versions for %1", (DeclAttribute, StringRef))
+
 ERROR(override_final,none,
       "%0 overrides a 'final' %1", (DescriptiveDeclKind, DescriptiveDeclKind))
 
@@ -3157,6 +3161,10 @@ ERROR(final_not_allowed_here,none,
       "'final' may only be applied to classes, properties, methods, and "
       "subscripts", ())
 
+ERROR(attr_incompatible_with_non_final,none,
+      "'%0' cannot be applied to a non-final %1",
+      (DeclAttribute, DescriptiveDeclKind))
+
 ERROR(final_not_on_accessors,none,
       "'final' cannot be applied to accessors, it must be put on the "
       "%select{var|let|subscript}0", (unsigned))
@@ -5615,6 +5623,14 @@ ERROR(availability_macro_in_inlinable, none,
       "availability macro cannot be used in inlinable %0",
       (DescriptiveDeclKind))
 
+ERROR(attr_requires_decl_availability_for_platform,none,
+      "'%0' requires that %1 have explicit availability for %2",
+      (DeclAttribute, DeclName, StringRef))
+
+ERROR(attr_requires_availability_for_platform,none,
+      "'%0' requires explicit availability for %1",
+      (DeclAttribute, StringRef))
+
 // This doesn't display as an availability diagnostic, but it's
 // implemented there and fires when these subscripts are marked
 // unavailable, so it seems appropriate to put it here.
@@ -6164,6 +6180,10 @@ ERROR(differentiable_programming_attr_used_without_required_module, none,
       "'@%0' attribute used without importing module %1",
       (StringRef, Identifier))
 
+//------------------------------------------------------------------------------
+// MARK: OSLog
+//------------------------------------------------------------------------------
+
 ERROR(oslog_arg_must_be_bool_literal, none,
       "argument must be a bool literal", ())
 ERROR(oslog_arg_must_be_integer_literal, none,
@@ -6271,5 +6291,13 @@ ERROR(cannot_convert_default_value_type_to_argument_type, none,
       "cannot convert default value of type %0 to expected argument type %1 for parameter #%2",
       (Type, Type, unsigned))
 
+//------------------------------------------------------------------------------
+// MARK: Back deployment
+//------------------------------------------------------------------------------
+
+ERROR(attr_incompatible_with_back_deploy,none,
+      "'%0' cannot be applied to a back deployed %1",
+      (DeclAttribute, DescriptiveDeclKind))
+
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

lib/AST/Decl.cpp

@@ -377,6 +377,18 @@ Decl::getIntroducedOSVersion(PlatformKind Kind) const {
   return None;
 }
 
+Optional<llvm::VersionTuple>
+Decl::getBackDeployBeforeOSVersion(PlatformKind Kind) const {
+  for (auto *attr : getAttrs()) {
+    if (auto *backDeployAttr = dyn_cast<BackDeployAttr>(attr)) {
+      if (backDeployAttr->Platform == Kind && backDeployAttr->Version) {
+        return backDeployAttr->Version;
+      }
+    }
+  }
+  return None;
+}
+
 llvm::raw_ostream &swift::operator<<(llvm::raw_ostream &OS,
                                      StaticSpellingKind SSK) {
   switch (SSK) {

lib/AST/DeclContext.cpp

@@ -424,8 +424,8 @@ swift::FragileFunctionKindRequest::evaluate(Evaluator &evaluator,
                 /*allowUsableFromInline=*/true};
       }
 
-      // If a property or subscript is @inlinable or @_alwaysEmitIntoClient,
-      // the accessors are @inlinable or @_alwaysEmitIntoClient also.
+      // Property and subscript accessors inherit @_alwaysEmitIntoClient,
+      // @_backDeploy, and @inlinable from their storage declarations.
       if (auto accessor = dyn_cast<AccessorDecl>(AFD)) {
         auto *storage = accessor->getStorage();
         if (storage->getAttrs().getAttribute<InlinableAttr>()) {
@@ -436,6 +436,10 @@ swift::FragileFunctionKindRequest::evaluate(Evaluator &evaluator,
           return {FragileFunctionKind::AlwaysEmitIntoClient,
                   /*allowUsableFromInline=*/true};
         }
+        if (storage->getAttrs().hasAttribute<BackDeployAttr>()) {
+          return {FragileFunctionKind::BackDeploy,
+                  /*allowUsableFromInline=*/true};
+        }
       }
     }
   }

lib/SILGen/SILGenApply.cpp

@@ -1030,10 +1030,8 @@ class SILGenApply : public Lowering::ExprVisitor<SILGenApply> {
   }
 
   void processClassMethod(DeclRefExpr *e, AbstractFunctionDecl *afd) {
-    // FIXME(backDeploy): Investigate support for back deployed class method
-    // calls
     assert(!afd->isBackDeployed() &&
-           "back deployed method calls are unsupported");
+           "cannot back deploy dynamically dispatched methods");
 
     ArgumentSource selfArgSource(selfApply->getBase());
     setSelfParam(std::move(selfArgSource));

lib/SILGen/SILGenBackDeploy.cpp

@@ -53,10 +53,10 @@ static void emitBackDeployIfAvailableCondition(SILGenFunction &SGF,
                                                SILBasicBlock *availableBB,
                                                SILBasicBlock *unavailableBB) {
   PlatformKind platform = targetPlatform(SGF.SGM.getASTContext().LangOpts);
-  auto introduced = AFD->getIntroducedOSVersion(platform);
+  auto version = AFD->getBackDeployBeforeOSVersion(platform);
   VersionRange OSVersion = VersionRange::empty();
-  if (introduced.hasValue()) {
-    OSVersion = VersionRange::allGTE(*introduced);
+  if (version.hasValue()) {
+    OSVersion = VersionRange::allGTE(*version);
   }
 
   SILValue booleanTestValue;