Sema: Update more diagnostics for @cdecl and representability in the C language

include/swift/AST/DiagnosticsCommon.h

@@ -55,6 +55,7 @@ namespace swift {
   } // end namespace detail
 
   enum class StaticSpellingKind : uint8_t;
+  enum class ForeignLanguage : uint8_t;
 
   namespace diag {
 

include/swift/AST/DiagnosticsSema.def

@@ -5512,11 +5512,15 @@ FIXIT(insert_globalactor_attr, "@%0 ", (Type))
 ERROR(main_function_must_be_mainActor,none,
       "main() must be '@MainActor'", ())
 
+// Keep aligned with enum ForeignLanguage
+#define FOREIGN_LANG_SELECT "select{C|Objective-C}"
+
 ERROR(not_objc_function_async,none,
       "'async' %kindonly0 cannot be represented in Objective-C",
       (const AbstractFunctionDecl *))
 NOTE(not_objc_function_type_async,none,
-      "'async' function types cannot be represented in Objective-C", ())
+     "'async' function types cannot be represented "
+     "in %" FOREIGN_LANG_SELECT "0", (ForeignLanguage))
 ERROR(actor_isolated_objc,none,
       "actor-isolated %kind0 cannot be '@objc'",
        (const ValueDecl *))
@@ -6529,9 +6533,6 @@ ERROR(objc_cannot_infer_name_raw_identifier,none,
 // If you change this, also change enum ObjCReason
 #define OBJC_ATTR_SELECT "select{marked '@cdecl'|marked '@_cdecl'|marked dynamic|marked '@objc'|marked '@objcMembers'|marked '@IBOutlet'|marked '@IBAction'|marked '@IBSegueAction'|marked '@NSManaged'|a member of an '@objc' protocol|implicitly '@objc'|an '@objc' override|an implementation of an '@objc' requirement|marked '@IBInspectable'|marked '@GKInspectable'|in an '@objc' extension of a class (without '@nonobjc')|in an '@objc @implementation' extension of a class (without final or '@nonobjc')|marked '@objc' by an access note}"
 
-// Keep aligned with enum ForeignLanguage
-#define FOREIGN_LANG_SELECT "select{C|Objective-C}"
-
 ERROR(objc_invalid_on_var,none,
       "property cannot be %" OBJC_ATTR_SELECT "0 "
       "because its type cannot be represented in Objective-C", (unsigned))
@@ -6566,25 +6567,32 @@ NOTE(not_objc_error_protocol_composition,none,
      "protocol-constrained type containing 'Error' cannot be represented "
      "in Objective-C", ())
 NOTE(not_objc_empty_tuple,none,
-      "empty tuple type cannot be represented in Objective-C", ())
+     "empty tuple type cannot be represented in %" FOREIGN_LANG_SELECT "0",
+     (ForeignLanguage))
 NOTE(not_objc_non_trivial_cxx_class,none,
-     "non-trivial C++ classes cannot be represented in Objective-C", ())
+     "non-trivial C++ classes cannot be represented in "
+     "%" FOREIGN_LANG_SELECT "0",
+     (ForeignLanguage))
 NOTE(not_objc_tuple,none,
-      "tuples cannot be represented in Objective-C", ())
+     "tuples cannot be represented in %" FOREIGN_LANG_SELECT "0",
+     (ForeignLanguage))
 NOTE(not_objc_swift_class,none,
      "classes not annotated with '@objc' cannot be represented "
      "in Objective-C", ())
 NOTE(not_objc_swift_struct,none,
-      "Swift structs cannot be represented in Objective-C", ())
+      "Swift structs cannot be represented in %" FOREIGN_LANG_SELECT "0",
+     (ForeignLanguage))
 NOTE(not_objc_swift_enum,none,
       "non-'@objc' enums cannot be represented in Objective-C", ())
 NOTE(not_objc_generic_type_param,none,
-     "generic type parameters cannot be represented in Objective-C", ())
+     "generic type parameters cannot be represented in "
+     "%" FOREIGN_LANG_SELECT "0", (ForeignLanguage))
 NOTE(not_objc_function_type_param,none,
-     "function types cannot be represented in Objective-C unless their "
-     "parameters and returns can be", ())
+     "function types cannot be represented in %" FOREIGN_LANG_SELECT "0 "
+     "unless their parameters and returns can be", (ForeignLanguage))
 NOTE(not_objc_function_type_throwing,none,
-      "throwing function types cannot be represented in Objective-C", ())
+     "throwing function types cannot be represented in "
+     "%" FOREIGN_LANG_SELECT "0", (ForeignLanguage))
 NOTE(objc_inferring_on_objc_protocol_member,none,
      "inferring '@objc' because the declaration is a member of "
      "an '@objc' protocol", ())
@@ -6594,6 +6602,11 @@ NOTE(objc_witness_objc_requirement,none,
      "satisfying requirement for %kind0 in protocol %1",
      (const ValueDecl *, const ProtocolDecl *))
 
+NOTE(cdecl_incompatible_with_protocols,none,
+     "protocols cannot be represented in C", ())
+NOTE(cdecl_incompatible_with_classes,none,
+     "classes cannot be represented in C", ())
+
 ERROR(no_opaque_return_type_of,none,
       "unable to resolve type for _opaqueReturnTypeOf attribute", ())
 
@@ -6607,24 +6620,24 @@ ERROR(objc_addressor, none,
 ERROR(objc_coroutine_accessor, none,
       "'read' and 'modify' accessors are not allowed to be marked '@objc'", ())
 ERROR(objc_invalid_on_func_variadic,none,
-      "method cannot be %" OBJC_ATTR_SELECT "0 because it has a variadic "
-      "parameter", (unsigned))
+      "%kindonly0 cannot be %" OBJC_ATTR_SELECT "1 because it has a variadic "
+      "parameter", (const AbstractFunctionDecl*, unsigned))
 ERROR(objc_invalid_on_func_inout,none,
       "%kindonly0 cannot be %" OBJC_ATTR_SELECT "1 because inout "
       "parameters cannot be represented in %" FOREIGN_LANG_SELECT "2",
-      (const AbstractFunctionDecl*, unsigned, unsigned))
+      (const AbstractFunctionDecl*, unsigned, ForeignLanguage))
 ERROR(objc_invalid_on_func_param_type,none,
       "%kindonly0 cannot be %" OBJC_ATTR_SELECT "2 because the type of the "
       "parameter %1 cannot be represented in %" FOREIGN_LANG_SELECT "3",
-      (const AbstractFunctionDecl*, unsigned, unsigned, unsigned))
+      (const AbstractFunctionDecl*, unsigned, unsigned, ForeignLanguage))
 ERROR(objc_invalid_on_func_single_param_type,none,
       "%kindonly0 cannot be %" OBJC_ATTR_SELECT "1 because the type of the "
       "parameter cannot be represented in %" FOREIGN_LANG_SELECT "2",
-      (const AbstractFunctionDecl*, unsigned, unsigned))
+      (const AbstractFunctionDecl*, unsigned, ForeignLanguage))
 ERROR(objc_invalid_on_func_result_type,none,
       "%kindonly0 cannot be %" OBJC_ATTR_SELECT "1 because its result type "
       "cannot be represented in %" FOREIGN_LANG_SELECT "2",
-      (const AbstractFunctionDecl*, unsigned, unsigned))
+      (const AbstractFunctionDecl*, unsigned, ForeignLanguage))
 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))

include/swift/AST/Type.h

@@ -161,7 +161,7 @@ inline SubstOptions operator|(SubstFlags lhs, SubstFlags rhs) {
 
 /// Enumeration describing foreign languages to which Swift may be
 /// bridged.
-enum class ForeignLanguage {
+enum class ForeignLanguage : uint8_t {
   C,
   ObjectiveC,
 };

lib/Sema/TypeCheckDeclObjC.cpp

@@ -170,24 +170,32 @@ void ObjCReason::setAttrInvalid() const {
 static void diagnoseTypeNotRepresentableInObjC(const DeclContext *DC,
                                                Type T,
                                                SourceRange TypeRange,
-                                               DiagnosticBehavior behavior) {
+                                               DiagnosticBehavior behavior,
+                                               ObjCReason reason) {
   auto &diags = DC->getASTContext().Diags;
+  auto language = reason.getForeignLanguage();
 
   // Special diagnostic for tuples.
   if (T->is<TupleType>()) {
     if (T->isVoid())
-      diags.diagnose(TypeRange.Start, diag::not_objc_empty_tuple)
+      diags.diagnose(TypeRange.Start, diag::not_objc_empty_tuple, language)
           .highlight(TypeRange)
           .limitBehavior(behavior);
     else
-      diags.diagnose(TypeRange.Start, diag::not_objc_tuple)
+      diags.diagnose(TypeRange.Start, diag::not_objc_tuple, language)
           .highlight(TypeRange)
           .limitBehavior(behavior);
     return;
   }
 
   // Special diagnostic for classes.
   if (auto *CD = T->getClassOrBoundGenericClass()) {
+    if (language == ForeignLanguage::C) {
+      diags.diagnose(TypeRange.Start, diag::cdecl_incompatible_with_classes)
+          .limitBehavior(behavior);
+      return;
+    }
+
     if (!CD->isObjC())
       diags.diagnose(TypeRange.Start, diag::not_objc_swift_class)
           .highlight(TypeRange)
@@ -199,12 +207,14 @@ static void diagnoseTypeNotRepresentableInObjC(const DeclContext *DC,
   if (auto *SD = T->getStructOrBoundGenericStruct()) {
     if (isa_and_nonnull<clang::CXXRecordDecl>(SD->getClangDecl())) {
       // This can be a non-trivial C++ record.
-      diags.diagnose(TypeRange.Start, diag::not_objc_non_trivial_cxx_class)
+      diags.diagnose(TypeRange.Start, diag::not_objc_non_trivial_cxx_class,
+                     language)
           .highlight(TypeRange)
           .limitBehavior(behavior);
       return;
     }
-    diags.diagnose(TypeRange.Start, diag::not_objc_swift_struct)
+    diags.diagnose(TypeRange.Start, diag::not_objc_swift_struct,
+                   language)
         .highlight(TypeRange)
         .limitBehavior(behavior);
     return;
@@ -220,6 +230,13 @@ static void diagnoseTypeNotRepresentableInObjC(const DeclContext *DC,
 
   // Special diagnostic for protocols and protocol compositions.
   if (T->isExistentialType()) {
+    // No protocol is representable in C.
+    if (language == ForeignLanguage::C) {
+      diags.diagnose(TypeRange.Start, diag::cdecl_incompatible_with_protocols)
+          .limitBehavior(behavior);
+      return;
+    }
+
     if (T->isAny()) {
       // Any is not @objc.
       diags.diagnose(TypeRange.Start,
@@ -267,28 +284,32 @@ static void diagnoseTypeNotRepresentableInObjC(const DeclContext *DC,
   }
 
   if (T->is<ArchetypeType>() || T->isTypeParameter()) {
-    diags.diagnose(TypeRange.Start, diag::not_objc_generic_type_param)
+    diags.diagnose(TypeRange.Start, diag::not_objc_generic_type_param,
+                   language)
         .highlight(TypeRange)
         .limitBehavior(behavior);
     return;
   }
 
   if (auto fnTy = T->getAs<FunctionType>()) {
     if (fnTy->getExtInfo().isAsync()) {
-      diags.diagnose(TypeRange.Start, diag::not_objc_function_type_async)
+      diags.diagnose(TypeRange.Start, diag::not_objc_function_type_async,
+                     language)
         .highlight(TypeRange)
         .limitBehavior(behavior);
       return;
     }
 
     if (fnTy->getExtInfo().isThrowing()) {
-      diags.diagnose(TypeRange.Start, diag::not_objc_function_type_throwing)
+      diags.diagnose(TypeRange.Start, diag::not_objc_function_type_throwing,
+                     language)
         .highlight(TypeRange)
         .limitBehavior(behavior);
       return;
     }
 
-    diags.diagnose(TypeRange.Start, diag::not_objc_function_type_param)
+    diags.diagnose(TypeRange.Start, diag::not_objc_function_type_param,
+                   language)
       .highlight(TypeRange)
       .limitBehavior(behavior);
     return;
@@ -305,25 +326,26 @@ static void diagnoseFunctionParamNotRepresentable(
     softenIfAccessNote(AFD, Reason.getAttr(),
       AFD->diagnose(diag::objc_invalid_on_func_single_param_type,
                     AFD, getObjCDiagnosticAttrKind(Reason),
-                    (unsigned)language)
+                    language)
           .limitBehavior(behavior));
   } else {
     softenIfAccessNote(AFD, Reason.getAttr(),
       AFD->diagnose(diag::objc_invalid_on_func_param_type,
                     AFD, ParamIndex + 1, getObjCDiagnosticAttrKind(Reason),
-                    (unsigned)language)
+                    language)
           .limitBehavior(behavior));
   }
   SourceRange SR;
 
   if (P->hasAttachedPropertyWrapper()) {
     auto wrapperTy = P->getPropertyWrapperBackingPropertyType();
     SR = P->getOutermostAttachedPropertyWrapper()->getRange();
-    diagnoseTypeNotRepresentableInObjC(AFD, wrapperTy, SR, behavior);
+    diagnoseTypeNotRepresentableInObjC(AFD, wrapperTy, SR, behavior, Reason);
   } else {
     if (auto typeRepr = P->getTypeRepr())
       SR = typeRepr->getSourceRange();
-    diagnoseTypeNotRepresentableInObjC(AFD, P->getTypeInContext(), SR, behavior);
+    diagnoseTypeNotRepresentableInObjC(AFD, P->getTypeInContext(), SR,
+                                       behavior, Reason);
   }
   Reason.describe(AFD);
 }
@@ -345,7 +367,7 @@ static bool isParamListRepresentableInLanguage(const AbstractFunctionDecl *AFD,
     if (param->isVariadic()) {
       softenIfAccessNote(AFD, Reason.getAttr(),
         diags.diagnose(param->getStartLoc(), diag::objc_invalid_on_func_variadic,
-                       getObjCDiagnosticAttrKind(Reason))
+                       AFD, getObjCDiagnosticAttrKind(Reason))
           .highlight(param->getSourceRange())
           .limitBehavior(behavior));
       Reason.describe(AFD);
@@ -358,7 +380,7 @@ static bool isParamListRepresentableInLanguage(const AbstractFunctionDecl *AFD,
       softenIfAccessNote(AFD, Reason.getAttr(),
         diags.diagnose(param->getStartLoc(), diag::objc_invalid_on_func_inout,
                        AFD, getObjCDiagnosticAttrKind(Reason),
-                       (unsigned)language)
+                       language)
           .highlight(param->getSourceRange())
           .limitBehavior(behavior));
       Reason.describe(AFD);
@@ -800,11 +822,11 @@ bool swift::isRepresentableInLanguage(
       softenIfAccessNote(AFD, Reason.getAttr(),
        AFD->diagnose(diag::objc_invalid_on_func_result_type,
                      FD, getObjCDiagnosticAttrKind(Reason),
-                     (unsigned)language)
+                     language)
             .limitBehavior(behavior));
       diagnoseTypeNotRepresentableInObjC(FD, ResultType,
                                          FD->getResultTypeSourceRange(),
-                                         behavior);
+                                         behavior, Reason);
       Reason.describe(FD);
       return false;
     }
@@ -857,11 +879,11 @@ bool swift::isRepresentableInLanguage(
         softenIfAccessNote(AFD, Reason.getAttr(),
           AFD->diagnose(diag::objc_invalid_on_func_result_type,
                         FD, getObjCDiagnosticAttrKind(Reason),
-                        (unsigned)language)
+                        language)
               .limitBehavior(behavior));
         diagnoseTypeNotRepresentableInObjC(FD, type,
                                            FD->getResultTypeSourceRange(),
-                                           behavior);
+                                           behavior, Reason);
         Reason.describe(FD);
 
         return true;
@@ -1168,7 +1190,7 @@ bool swift::isRepresentableInObjC(const VarDecl *VD, ObjCReason Reason) {
           .limitBehavior(behavior));
     diagnoseTypeNotRepresentableInObjC(VD->getDeclContext(),
                                        VD->getInterfaceType(),
-                                       TypeRange, behavior);
+                                       TypeRange, behavior, Reason);
     Reason.describe(VD);
   }
 
@@ -1256,7 +1278,7 @@ bool swift::isRepresentableInObjC(const SubscriptDecl *SD, ObjCReason Reason) {
     diagnoseTypeNotRepresentableInObjC(SD->getDeclContext(),
                                        !IndexResult ? IndexType
                                                     : ElementType,
-                                       TypeRange, behavior);
+                                       TypeRange, behavior, Reason);
     Reason.describe(SD);
   }