Treat references to enum cases with associated values as @Sendable functions

When `InferSendableFromCaptures`, make sure to treat references to enum
cases that have associated values as `@Sendable` functions.

Author: DougGregor

lib/Sema/ConstraintSystem.cpp

@@ -1710,8 +1710,16 @@ FunctionType *ConstraintSystem::adjustFunctionTypeForConcurrency(
       });
 
   if (Context.LangOpts.hasFeature(Feature::InferSendableFromCaptures)) {
+    DeclContext *DC = nullptr;
     if (auto *FD = dyn_cast<AbstractFunctionDecl>(decl)) {
-      auto *DC = FD->getDeclContext();
+      DC = FD->getDeclContext();
+    } else if (auto EED = dyn_cast<EnumElementDecl>(decl)) {
+      if (EED->hasAssociatedValues()) {
+        DC = EED->getDeclContext();
+      }
+    }
+
+    if (DC) {
       // All global functions should be @Sendable
       if (DC->isModuleScopeContext()) {
         if (!adjustedTy->getExtInfo().isSendable()) {

test/Concurrency/sendable_methods.swift

@@ -42,6 +42,7 @@ struct InferredSendableS: P {
 
 enum InferredSendableE: P {
   case a, b
+  case c(Int)
 
   func f() { }
 }
@@ -60,6 +61,13 @@ struct GenericS<T> : P {
   func g() async { }
 }
 
+enum GenericE<T> {
+  case a
+  case b(T)
+}
+
+extension GenericE: Sendable where T: Sendable { }
+
 class NonSendable {
   func f() {}
 }
@@ -265,3 +273,9 @@ do {
     true ? nil : c // Ok
   }
 }
+
+func acceptSendableFunc<T, U>(_: @Sendable (T) -> U) { }
+
+acceptSendableFunc(InferredSendableE.c)
+acceptSendableFunc(GenericE<Int>.b)
+acceptSendableFunc(GenericE<NonSendable>.b)