Async await prototype

docs/ABI/Mangling.rst

@@ -316,12 +316,13 @@ Types
   FUNCTION-KIND ::= 'B'                      // objc block function type
   FUNCTION-KIND ::= 'C'                      // C function pointer type
 
-  function-signature ::= params-type params-type throws? // results and parameters
+  function-signature ::= params-type params-type throws? async? // results and parameters
 
   params-type := type                        // tuple in case of multiple parameters
   params-type := empty-list                  // shortcut for no parameters
 
   throws ::= 'K'                             // 'throws' annotation on function types
+  async ::= 'Y'                              // 'async' annotation on function types
 
   type-list ::= list-type '_' list-type*     // list of types
   type-list ::= empty-list

include/swift/ABI/MetadataValues.h

@@ -481,6 +481,7 @@ class TargetFunctionTypeFlags {
     ConventionMask   = 0x0F000000U,
     ConventionShift  = 24U,
     ThrowsMask       = 0x10000000U,
+    AsyncMask        = 0x20000000U,
   };
   int_type Data;
 
@@ -504,6 +505,12 @@ class TargetFunctionTypeFlags {
                                              (throws ? ThrowsMask : 0));
   }
 
+  constexpr TargetFunctionTypeFlags<int_type>
+  withAsync(bool async) const {
+    return TargetFunctionTypeFlags<int_type>((Data & AsyncMask) |
+                                             (async ? AsyncMask : 0));
+  }
+
   unsigned getNumArguments() const {
     return Data & NumArgumentsMask;
   }
@@ -515,6 +522,9 @@ class TargetFunctionTypeFlags {
   bool throws() const {
     return bool(Data & ThrowsMask);
   }
+  bool isAsync() const {
+    return bool(Data & AsyncMask);
+  }
 
   int_type getIntValue() const {
     return Data;

include/swift/AST/Decl.h

@@ -233,7 +233,7 @@ bool conflicting(const OverloadSignature& sig1, const OverloadSignature& sig2);
 class alignas(1 << DeclAlignInBits) Decl {
   class DeclBitfields {
     friend class Decl;
-    unsigned Kind : 6;
+    unsigned Kind : 5;
 
     /// \brief Whether this declaration is invalid.
     unsigned Invalid : 1;
@@ -262,7 +262,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// DeclContext of an active #if config clause.
     unsigned EscapedFromIfConfig : 1;
   };
-  enum { NumDeclBits = 13 };
+  enum { NumDeclBits = 12 };
   static_assert(NumDeclBits <= 32, "fits in an unsigned");
 
   class PatternBindingDeclBitfields {
@@ -334,7 +334,6 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// \brief Whether this is a property used in expressions in the debugger.
     /// It is up to the debugger to instruct SIL how to access this variable.
     unsigned IsDebuggerVar : 1;
-
   };
   enum { NumVarDeclBits = NumAbstractStorageDeclBits + 6 };
   static_assert(NumVarDeclBits <= 32, "fits in an unsigned");
@@ -369,13 +368,16 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// Whether the function body throws.
     unsigned Throws : 1;
 
+    /// Whether the function body is async.
+    unsigned IsAsync : 1;
+
     /// Whether this function requires a new vtable entry.
     unsigned NeedsNewVTableEntry : 1;
 
     /// Whether NeedsNewVTableEntry is valid.
     unsigned HasComputedNeedsNewVTableEntry : 1;
   };
-  enum { NumAbstractFunctionDeclBits = NumValueDeclBits + 13 };
+  enum { NumAbstractFunctionDeclBits = NumValueDeclBits + 14 };
   static_assert(NumAbstractFunctionDeclBits <= 32, "fits in an unsigned");
 
   class FuncDeclBitfields {
@@ -659,6 +661,7 @@ class alignas(1 << DeclAlignInBits) Decl {
   Decl(DeclKind kind, llvm::PointerUnion<DeclContext *, ASTContext *> context)
     : OpaqueBits(0), Context(context) {
     DeclBits.Kind = unsigned(kind);
+    assert(DeclBits.Kind == unsigned(kind) && "Too few bits for kind");
     DeclBits.Invalid = false;
     DeclBits.Implicit = false;
     DeclBits.FromClang = false;
@@ -4838,23 +4841,25 @@ class AbstractFunctionDecl : public ValueDecl, public GenericContext {
 
   CaptureInfo Captures;
 
-  /// Location of the 'throws' token.
-  SourceLoc ThrowsLoc;
+  /// Location of the 'throws' and 'async' tokens (if present).
+  SourceLoc ThrowsLoc, AsyncLoc;
 
   ImportAsMemberStatus IAMStatus;
 
   AbstractFunctionDecl(DeclKind Kind, DeclContext *Parent, DeclName Name,
                        SourceLoc NameLoc, bool Throws, SourceLoc ThrowsLoc,
+                       bool isAsync, SourceLoc AsyncLoc,
                        unsigned NumParameterLists,
                        GenericParamList *GenericParams)
       : ValueDecl(Kind, Parent, Name, NameLoc),
         GenericContext(DeclContextKind::AbstractFunctionDecl, Parent),
-        Body(nullptr), ThrowsLoc(ThrowsLoc) {
+        Body(nullptr), ThrowsLoc(ThrowsLoc), AsyncLoc(AsyncLoc) {
     setBodyKind(BodyKind::None);
     setGenericParams(GenericParams);
     AbstractFunctionDeclBits.NumParameterLists = NumParameterLists;
     AbstractFunctionDeclBits.Overridden = false;
     AbstractFunctionDeclBits.Throws = Throws;
+    AbstractFunctionDeclBits.IsAsync = isAsync;
     AbstractFunctionDeclBits.NeedsNewVTableEntry = false;
     AbstractFunctionDeclBits.HasComputedNeedsNewVTableEntry = false;
 
@@ -4890,10 +4895,15 @@ class AbstractFunctionDecl : public ValueDecl, public GenericContext {
 public:
   /// Retrieve the location of the 'throws' keyword, if present.
   SourceLoc getThrowsLoc() const { return ThrowsLoc; }
+  /// Retrieve the location of the 'async' keyword, if present.
+  SourceLoc getAsyncLoc() const { return AsyncLoc; }
 
   /// Returns true if the function body throws.
   bool hasThrows() const { return AbstractFunctionDeclBits.Throws; }
 
+  /// Returns true if the function body is async.
+  bool isAsync() const { return AbstractFunctionDeclBits.IsAsync; }
+
   // FIXME: Hack that provides names with keyword arguments for accessors.
   DeclName getEffectiveFullName() const;
 
@@ -5144,12 +5154,13 @@ class FuncDecl final : public AbstractFunctionDecl,
            SourceLoc FuncLoc,
            DeclName Name, SourceLoc NameLoc,
            bool Throws, SourceLoc ThrowsLoc,
+           bool IsAsync, SourceLoc AsyncLoc,
            SourceLoc AccessorKeywordLoc,
            unsigned NumParameterLists,
            GenericParamList *GenericParams, DeclContext *Parent)
     : AbstractFunctionDecl(DeclKind::Func, Parent,
                            Name, NameLoc,
-                           Throws, ThrowsLoc,
+                           Throws, ThrowsLoc, IsAsync, AsyncLoc,
                            NumParameterLists, GenericParams),
       StaticLoc(StaticLoc), FuncLoc(FuncLoc),
       AccessorKeywordLoc(AccessorKeywordLoc),
@@ -5170,6 +5181,7 @@ class FuncDecl final : public AbstractFunctionDecl,
                               SourceLoc FuncLoc,
                               DeclName Name, SourceLoc NameLoc,
                               bool Throws, SourceLoc ThrowsLoc,
+                              bool IsAsync, SourceLoc AsyncLoc,
                               SourceLoc AccessorKeywordLoc,
                               GenericParamList *GenericParams,
                               unsigned NumParameterLists,
@@ -5183,6 +5195,7 @@ class FuncDecl final : public AbstractFunctionDecl,
                                       SourceLoc FuncLoc,
                                       DeclName Name, SourceLoc NameLoc,
                                       bool Throws, SourceLoc ThrowsLoc,
+                                      bool IsAsync, SourceLoc AsyncLoc,
                                       SourceLoc AccessorKeywordLoc,
                                       GenericParamList *GenericParams,
                                       unsigned NumParameterLists,
@@ -5193,6 +5206,7 @@ class FuncDecl final : public AbstractFunctionDecl,
                           SourceLoc FuncLoc,
                           DeclName Name, SourceLoc NameLoc,
                           bool Throws, SourceLoc ThrowsLoc,
+                          bool IsAsync, SourceLoc AsyncLoc,
                           SourceLoc AccessorKeywordLoc,
                           GenericParamList *GenericParams,
                           ArrayRef<ParameterList *> ParameterLists,
@@ -5649,6 +5663,7 @@ class ConstructorDecl : public AbstractFunctionDecl {
   ConstructorDecl(DeclName Name, SourceLoc ConstructorLoc, 
                   OptionalTypeKind Failability, SourceLoc FailabilityLoc,
                   bool Throws, SourceLoc ThrowsLoc,
+                  bool IsAsync, SourceLoc AsyncLoc,
                   ParamDecl *SelfParam, ParameterList *BodyParams,
                   GenericParamList *GenericParams, 
                   DeclContext *Parent);

include/swift/AST/DiagnosticsParse.def

@@ -697,8 +697,10 @@ ERROR(generic_non_function,PointsToFirstBadToken,
 ERROR(rethrowing_function_type,none,
       "only function declarations may be marked 'rethrows'; "
       "did you mean 'throws'?", ())
-ERROR(throws_in_wrong_position,none,
-      "'throws' may only occur before '->'", ())
+ERROR(func_type_specifier_redundant,none,
+      "redundant function type specifier", ())
+ERROR(throwsasync_in_wrong_position,none,
+      "'%select{async|throws}0' may only occur before '->'", (bool))
 ERROR(rethrows_in_wrong_position,none,
       "'rethrows' may only occur before '->'", ())
 ERROR(throw_in_function_type,none,
@@ -1181,6 +1183,10 @@ ERROR(expected_colon_after_if_question,none,
       "expected ':' after '? ...' in ternary expression", ())
 ERROR(expected_expr_after_if_colon,none,
       "expected expression after '? ... :' in ternary expression", ())
+ERROR(expected_expr_after_try, none,
+      "expected expression after 'try'", ())
+ERROR(expected_expr_after_await, none,
+      "expected expression after 'await'", ())
 
 // Cast expressions
 ERROR(expected_type_after_is,none,

include/swift/AST/DiagnosticsSema.def

@@ -414,6 +414,12 @@ ERROR(cannot_convert_assign_nil,none,
 ERROR(throws_functiontype_mismatch,none,
       "invalid conversion from throwing function of type %0 to "
       "non-throwing function type %1", (Type, Type))
+ERROR(async_functiontype_removal,none,
+      "invalid removal of 'async' when converting function of type %0 to %1",
+      (Type, Type))
+ERROR(async_functiontype_addition,none,
+      "invalid addition of 'async' when converting function of type %0 to %1",
+      (Type, Type))
 ERROR(noescape_functiontype_mismatch,none,
       "invalid conversion from non-escaping function of type %0 to "
       "potentially escaping function type %1", (Type, Type))
@@ -1580,6 +1586,8 @@ NOTE(protocol_witness_rethrows_conflict,none,
      "candidate is not 'rethrows', but protocol requires it", ())
 NOTE(protocol_witness_throws_conflict,none,
      "candidate throws, but protocol does not allow it", ())
+NOTE(protocol_witness_async_conflict,none,
+     "candidate and protocol requirement are not both 'async'", ())
 NOTE(protocol_witness_not_objc,none,
      "candidate is explicitly '@nonobjc'", ())
 
@@ -1871,6 +1879,9 @@ ERROR(override_class_declaration_in_extension,none,
 WARNING(override_class_declaration_in_extension_warning,none,
       "cannot override a non-dynamic class declaration from an extension",
       ())
+ERROR(override_async,none,
+      "cannot override %1async %select{method|initializer}0 with "
+      "%2async %select{method|initializer}0", (bool, StringRef, StringRef))
 ERROR(override_throws,none,
       "cannot override non-throwing %select{method|initializer}0 with "
       "throwing %select{method|initializer}0", (bool))
@@ -2412,7 +2423,7 @@ ERROR(missing_builtin_precedence_group,none,
       (Identifier))
 
 // If you change this, also change enum TryKindForDiagnostics.
-#define TRY_KIND_SELECT(SUB) "%select{try|try!|try?}" #SUB
+#define TRY_KIND_SELECT(SUB) "%select{try|try!|try?|await}" #SUB
 
 ERROR(try_rhs,none,
       "'" TRY_KIND_SELECT(0) "' cannot appear to the right of a "
@@ -3021,6 +3032,14 @@ NOTE(note_error_to_optional,none,
       "did you mean to handle error as optional value?", ())
 NOTE(note_disable_error_propagation,none,
       "did you mean to disable error propagation?", ())
+ERROR(async_call_without_await,none,
+      "call is 'async' but is not marked with 'await'", ())
+WARNING(no_async_in_await,none,
+        "no calls to 'async' functions occur within 'await' expression", ())
+ERROR(async_call_in_illegal_context,none,
+      "async expression is not allowed in %0",
+      (StringRef))
+
 
 WARNING(no_throw_in_try,none,
         "no calls to throwing functions occur within 'try' expression", ())
@@ -3298,6 +3317,9 @@ NOTE(not_objc_function_type_param,none,
      "parameters and returns can be", ())
 NOTE(not_objc_function_type_throwing,none,
       "throwing function types cannot be represented in Objective-C", ())
+NOTE(not_objc_function_type_async,none,
+     "async function types cannot be represented in Objective-C", ())
+
 NOTE(objc_inferring_on_objc_protocol_member,none,
      "inferring '@objc' because the declaration is a member of "
      "an '@objc' protocol", ())
@@ -3332,6 +3354,9 @@ ERROR(objc_invalid_on_func_single_param_type,none,
 ERROR(objc_invalid_on_func_result_type,none,
       "method cannot be %" OBJC_ATTR_SELECT "0 because its result type "
       "cannot be represented in Objective-C", (unsigned))
+ERROR(objc_invalid_on_async_func,none,
+      "method cannot be %" OBJC_ATTR_SELECT "0 because it is async",
+      (unsigned))
 ERROR(objc_invalid_on_foreign_class,none,
       "method cannot be %" OBJC_ATTR_SELECT "0 because Core Foundation "
       "types are not classes in Objective-C", (unsigned))