Merge pull request swiftlang#81863 from xedin/using-for-default-isolation-in-file-context

[AST/Sema] SE-0478:  Implement `using` declaration under an experimental flag

Author: xedin

SwiftCompilerSources/Sources/AST/Declarations.swift

@@ -124,6 +124,8 @@ final public class TopLevelCodeDecl: Decl {}
 
 final public class ImportDecl: Decl {}
 
+final public class UsingDecl: Decl {}
+
 final public class PrecedenceGroupDecl: Decl {}
 
 final public class MissingDecl: Decl {}

SwiftCompilerSources/Sources/AST/Registration.swift

@@ -36,6 +36,7 @@ public func registerAST() {
   registerDecl(ExtensionDecl.self)
   registerDecl(TopLevelCodeDecl.self)
   registerDecl(ImportDecl.self)
+  registerDecl(UsingDecl.self)
   registerDecl(PrecedenceGroupDecl.self)
   registerDecl(MissingDecl.self)
   registerDecl(MissingMemberDecl.self)

include/swift/AST/ASTBridging.h

@@ -1744,6 +1744,19 @@ BridgedImportDecl BridgedImportDecl_createParsed(
     BridgedSourceLoc cImportKeywordLoc, BridgedImportKind cImportKind,
     BridgedSourceLoc cImportKindLoc, BridgedArrayRef cImportPathElements);
 
+enum ENUM_EXTENSIBILITY_ATTR(open) BridgedUsingSpecifier {
+  BridgedUsingSpecifierMainActor,
+  BridgedUsingSpecifierNonisolated,
+};
+
+SWIFT_NAME("BridgedUsingDecl.createParsed(_:declContext:usingKeywordLoc:"
+           "specifierLoc:specifier:)")
+BridgedUsingDecl BridgedUsingDecl_createParsed(BridgedASTContext cContext,
+                                               BridgedDeclContext cDeclContext,
+                                               BridgedSourceLoc usingKeywordLoc,
+                                               BridgedSourceLoc specifierLoc,
+                                               BridgedUsingSpecifier specifier);
+
 SWIFT_NAME("BridgedSubscriptDecl.createParsed(_:declContext:staticLoc:"
            "staticSpelling:subscriptKeywordLoc:genericParamList:parameterList:"
            "arrowLoc:returnType:genericWhereClause:)")

include/swift/AST/Decl.h

@@ -213,7 +213,8 @@ enum class DescriptiveDeclKind : uint8_t {
   OpaqueResultType,
   OpaqueVarType,
   Macro,
-  MacroExpansion
+  MacroExpansion,
+  Using
 };
 
 /// Describes which spelling was used in the source for the 'static' or 'class'
@@ -267,6 +268,16 @@ static_assert(uint8_t(SelfAccessKind::LastSelfAccessKind) <
               "Self Access Kind is too small to fit in SelfAccess kind bits. "
               "Please expand ");
 
+enum class UsingSpecifier : uint8_t {
+  MainActor,
+  Nonisolated,
+  LastSpecifier = Nonisolated,
+};
+enum : unsigned {
+  NumUsingSpecifierBits =
+      countBitsUsed(static_cast<unsigned>(UsingSpecifier::LastSpecifier))
+};
+
 /// Diagnostic printing of \c SelfAccessKind.
 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, SelfAccessKind SAK);
 
@@ -827,6 +838,10 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl>, public Swi
     NumPathElements : 8
   );
 
+  SWIFT_INLINE_BITFIELD(UsingDecl, Decl, NumUsingSpecifierBits,
+    Specifier : NumUsingSpecifierBits
+  );
+
   SWIFT_INLINE_BITFIELD(ExtensionDecl, Decl, 4+1,
     /// An encoding of the default and maximum access level for this extension.
     /// The value 4 corresponds to AccessLevel::Public
@@ -9737,6 +9752,34 @@ class MacroExpansionDecl : public Decl, public FreestandingMacroExpansion {
   }
 };
 
+/// UsingDecl - This represents a single `using` declaration, e.g.:
+///   using @MainActor
+class UsingDecl : public Decl {
+  friend class Decl;
+
+private:
+  SourceLoc UsingLoc, SpecifierLoc;
+
+  UsingDecl(SourceLoc usingLoc, SourceLoc specifierLoc,
+            UsingSpecifier specifier, DeclContext *parent);
+
+public:
+  UsingSpecifier getSpecifier() const {
+    return static_cast<UsingSpecifier>(Bits.UsingDecl.Specifier);
+  }
+
+  std::string getSpecifierName() const;
+
+  SourceLoc getLocFromSource() const { return UsingLoc; }
+  SourceRange getSourceRange() const { return {UsingLoc, SpecifierLoc}; }
+
+  static UsingDecl *create(ASTContext &ctx, SourceLoc usingLoc,
+                           SourceLoc specifierLoc, UsingSpecifier specifier,
+                           DeclContext *parent);
+
+  static bool classof(const Decl *D) { return D->getKind() == DeclKind::Using; }
+};
+
 inline void
 AbstractStorageDecl::overwriteSetterAccess(AccessLevel accessLevel) {
   Accessors.setInt(accessLevel);

include/swift/AST/DeclExportabilityVisitor.h

@@ -158,6 +158,7 @@ class DeclExportabilityVisitor
   UNREACHABLE(MissingMember);
   UNREACHABLE(GenericTypeParam);
   UNREACHABLE(Param);
+  UNREACHABLE(Using);
 
 #undef UNREACHABLE
 

include/swift/AST/DeclNodes.def

@@ -190,6 +190,7 @@ DECL(Missing, Decl)
 DECL(MissingMember, Decl)
 DECL(PatternBinding, Decl)
 DECL(EnumCase, Decl)
+DECL(Using, Decl)
 
 ABSTRACT_DECL(Operator, Decl)
   OPERATOR_DECL(InfixOperator, OperatorDecl)

include/swift/AST/DiagnosticsParse.def

@@ -2187,5 +2187,14 @@ ERROR(nonisolated_nonsending_expected_rparen,PointsToFirstBadToken,
 ERROR(nonisolated_nonsending_repeated,none,
       "parameter may have at most one 'nonisolated(nonsending)' specifier", ())
 
+//------------------------------------------------------------------------------
+// MARK: using @<attribute> or using <identifier>
+//------------------------------------------------------------------------------
+ERROR(using_decl_invalid_specifier,PointsToFirstBadToken,
+      "default isolation can only be set to '@MainActor' or 'nonisolated'",
+      ())
+ERROR(experimental_using_decl_disabled,PointsToFirstBadToken,
+      "'using' is an experimental feature that is currently disabled", ())
+
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

include/swift/AST/DiagnosticsSema.def

@@ -8782,5 +8782,13 @@ ERROR(extensible_attr_on_internal_type,none,
 ERROR(pre_enum_extensibility_without_extensible,none,
       "%0 can only be used together with '@extensible' attribute", (DeclAttribute))
 
+//===----------------------------------------------------------------------===//
+// MARK: `using` declaration
+//===----------------------------------------------------------------------===//
+ERROR(invalid_redecl_of_file_isolation,none,
+      "invalid redeclaration of file-level default actor isolation", ())
+NOTE(invalid_redecl_of_file_isolation_prev,none,
+     "default isolation was previously declared here", ())
+
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

include/swift/AST/SourceFile.h

@@ -32,6 +32,7 @@ class GeneratedSourceInfo;
 class PersistentParserState;
 struct SourceFileExtras;
 class Token;
+enum class DefaultIsolation : uint8_t;
 
 /// Kind of import affecting how a decl can be reexported.
 ///
@@ -690,6 +691,11 @@ class SourceFile final : public FileUnit {
     DelayedParserState = std::move(state);
   }
 
+  /// Retrieve default action isolation to be used for this source file.
+  /// It's determine based on on top-level `using <<isolation>>` declaration
+  /// found in the file.
+  std::optional<DefaultIsolation> getDefaultIsolation() const;
+
   SWIFT_DEBUG_DUMP;
   void
   dump(raw_ostream &os,

include/swift/AST/TypeCheckRequests.h

@@ -5332,6 +5332,23 @@ class SemanticAvailabilitySpecRequest
   void cacheResult(std::optional<SemanticAvailabilitySpec> value) const;
 };
 
+class DefaultIsolationInSourceFileRequest
+    : public SimpleRequest<DefaultIsolationInSourceFileRequest,
+                           std::optional<DefaultIsolation>(const SourceFile *),
+                           RequestFlags::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  std::optional<DefaultIsolation> evaluate(Evaluator &evaluator,
+                                           const SourceFile *file) const;
+
+public:
+  bool isCached() const { return true; }
+};
+
 #define SWIFT_TYPEID_ZONE TypeChecker
 #define SWIFT_TYPEID_HEADER "swift/AST/TypeCheckerTypeIDZone.def"
 #include "swift/Basic/DefineTypeIDZone.h"