Concurrent functions don't need to ConcurrentValue parameters/results

Author: DougGregor

lib/Sema/TypeCheckAttr.cpp

@@ -129,6 +129,7 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
   IGNORED_ATTR(OriginallyDefinedIn)
   IGNORED_ATTR(NoDerivative)
   IGNORED_ATTR(SpecializeExtension)
+  IGNORED_ATTR(Concurrent)
 #undef IGNORED_ATTR
 
   void visitAlignmentAttr(AlignmentAttr *attr) {
@@ -420,22 +421,6 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
       }
     }
   }
-
-  void visitConcurrentAttr(ConcurrentAttr *attr) {
-    auto VD = dyn_cast<ValueDecl>(D);
-    if (!VD)
-      return;
-
-    auto innermostDC = VD->getInnermostDeclContext();
-    SubstitutionMap subs;
-    if (auto genericEnv = innermostDC->getGenericEnvironmentOfContext()) {
-      subs = genericEnv->getForwardingSubstitutionMap();
-    }
-
-    (void)diagnoseNonConcurrentTypesInReference(
-        ConcreteDeclRef(VD, subs), innermostDC, VD->getLoc(),
-        ConcurrentReferenceKind::ConcurrentFunction);
-  }
 };
 } // end anonymous namespace
 

test/Concurrency/concurrent_value_checking.swift

@@ -147,8 +147,7 @@ class SomeClass: MainActorProto {
 // ConcurrentValue restriction on concurrent functions.
 // ----------------------------------------------------------------------
 
-// FIXME: poor diagnostic
-@concurrent func concurrentFunc() -> NotConcurrent? { nil } // expected-warning{{cannot call function returning non-concurrent-value type 'NotConcurrent?' across actors}}
+@concurrent func concurrentFunc() -> NotConcurrent? { nil }
 
 // ----------------------------------------------------------------------
 // No ConcurrentValue restriction on @concurrent function types.