Describe ObjC reason for effectful properites

Author: beccadax

lib/Sema/TypeCheckDeclObjC.cpp

@@ -1049,7 +1049,9 @@ bool swift::isRepresentableInObjC(const VarDecl *VD, ObjCReason Reason) {
   // to mark them as @objc
   if (VD->getEffectfulGetAccessor()) {
     VD->diagnose(diag::effectful_not_representable_objc,
-                 VD->getDescriptiveKind());
+                 VD->getDescriptiveKind())
+        .limitBehavior(behavior);
+    Reason.describe(VD);
     return false;
   }
 
@@ -1088,7 +1090,9 @@ bool swift::isRepresentableInObjC(const SubscriptDecl *SD, ObjCReason Reason) {
   // to mark them as @objc
   if (SD->getEffectfulGetAccessor()) {
     SD->diagnose(diag::effectful_not_representable_objc,
-                 SD->getDescriptiveKind());
+                 SD->getDescriptiveKind())
+        .limitBehavior(behavior);
+    Reason.describe(SD);
     return false;
   }
 

test/decl/protocol/effectful_properties_objc.swift

@@ -5,10 +5,10 @@
 /////////
 // check for disallowed attributes in protocols
 @objc protocol Tea {
- var temperature : Double { get throws } // expected-error{{property with 'throws' or 'async' is not representable in Objective-C}}
- subscript(_ d : Double) -> Bool { get async throws } // expected-error{{subscript with 'throws' or 'async' is not representable in Objective-C}}
+ var temperature : Double { get throws } // expected-error{{property with 'throws' or 'async' is not representable in Objective-C}} expected-note{{inferring '@objc' because the declaration is a member of an '@objc' protocol}}
+ subscript(_ d : Double) -> Bool { get async throws } // expected-error{{subscript with 'throws' or 'async' is not representable in Objective-C}} expected-note{{inferring '@objc' because the declaration is a member of an '@objc' protocol}}
 
  // NOTE: this seems counter-intuitive, but TSPL says @nonobjc applies to
  // members that are representable in ObjC, and this is not representable.
- @nonobjc var sugar : Bool { get async } // expected-error{{property with 'throws' or 'async' is not representable in Objective-C}}
-}
+ @nonobjc var sugar : Bool { get async } // expected-error{{property with 'throws' or 'async' is not representable in Objective-C}} expected-note{{inferring '@objc' because the declaration is a member of an '@objc' protocol}}
+}