Sema: Requestify most checks on @_cdecl

Author: xymus

include/swift/AST/TypeCheckRequests.h

@@ -4853,6 +4853,25 @@ class TypeCheckObjCImplementationRequest
   bool isCached() const { return true; }
 };
 
+/// Check @cdecl-style attributes for compatibility with the foreign language.
+class TypeCheckCDeclAttributeRequest
+    : public SimpleRequest<TypeCheckCDeclAttributeRequest,
+                           evaluator::SideEffect(FuncDecl *FD,
+                                                 CDeclAttr *attr),
+                           RequestFlags::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  evaluator::SideEffect
+  evaluate(Evaluator &evaluator, FuncDecl *FD, CDeclAttr *attr) const;
+
+public:
+  bool isCached() const { return true; }
+};
+
 void simple_display(llvm::raw_ostream &out, ASTNode node);
 void simple_display(llvm::raw_ostream &out, Type value);
 void simple_display(llvm::raw_ostream &out, const TypeRepr *TyR);

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -550,6 +550,9 @@ SWIFT_REQUEST(TypeChecker, IsNonUserModuleRequest,
 SWIFT_REQUEST(TypeChecker, TypeCheckObjCImplementationRequest,
               unsigned(ExtensionDecl *),
               Cached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, TypeCheckCDeclAttributeRequest,
+              evaluator::SideEffect(FuncDecl *, CDeclAttr *),
+              Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, HasInitAccessorRequest,
               bool(AbstractStorageDecl *), Cached,
               NoLocationInfo)

lib/Sema/TypeCheckDeclObjC.cpp

@@ -4143,3 +4143,28 @@ evaluate(Evaluator &evaluator, Decl *D) const {
 
   return evaluator::SideEffect();
 }
+
+evaluator::SideEffect
+TypeCheckCDeclAttributeRequest::evaluate(Evaluator &evaluator,
+                                         FuncDecl *FD,
+                                         CDeclAttr *attr) const {
+  auto &ctx = FD->getASTContext();
+
+  std::optional<ForeignAsyncConvention> asyncConvention;
+  std::optional<ForeignErrorConvention> errorConvention;
+  ObjCReason reason(ObjCReason::ExplicitlyCDecl, attr);
+  if (isRepresentableInObjC(FD, reason, asyncConvention, errorConvention)) {
+    if (FD->hasAsync()) {
+      FD->setForeignAsyncConvention(*asyncConvention);
+      ctx.Diags.diagnose(attr->getLocation(), diag::attr_decl_async,
+                         attr, FD);
+    } else if (FD->hasThrows()) {
+      FD->setForeignErrorConvention(*errorConvention);
+      ctx.Diags.diagnose(attr->getLocation(), diag::cdecl_throws);
+    }
+  } else {
+    reason.setAttrInvalid();
+  }
+
+  return {};
+}

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -3781,24 +3781,10 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     }
 
     // If the function is exported to C, it must be representable in (Obj-)C.
-    // FIXME: This needs to be moved to its own request if we want to
-    // productize @_cdecl.
     if (auto CDeclAttr = FD->getAttrs().getAttribute<swift::CDeclAttr>()) {
-      std::optional<ForeignAsyncConvention> asyncConvention;
-      std::optional<ForeignErrorConvention> errorConvention;
-      ObjCReason reason(ObjCReason::ExplicitlyCDecl, CDeclAttr);
-      if (isRepresentableInObjC(FD, reason, asyncConvention, errorConvention)) {
-        if (FD->hasAsync()) {
-          FD->setForeignAsyncConvention(*asyncConvention);
-          Ctx.Diags.diagnose(CDeclAttr->getLocation(), diag::attr_decl_async,
-                             CDeclAttr, FD);
-        } else if (FD->hasThrows()) {
-          FD->setForeignErrorConvention(*errorConvention);
-          Ctx.Diags.diagnose(CDeclAttr->getLocation(), diag::cdecl_throws);
-        }
-      } else {
-        reason.setAttrInvalid();
-      }
+      evaluateOrDefault(Ctx.evaluator,
+                        TypeCheckCDeclAttributeRequest{FD, CDeclAttr},
+                        {});
     }
 
     TypeChecker::checkObjCImplementation(FD);