Merge pull request #83110 from swiftlang/jepa-release

[6.2] Sema: Make `@concurrent` not imply `async` on closures

lib/Sema/ConstraintSystem.cpp

@@ -1438,17 +1438,11 @@ FunctionType::ExtInfo ClosureEffectsRequest::evaluate(
   if (!body)
     return ASTExtInfoBuilder().withSendable(sendable).build();
 
-  // `@concurrent` attribute is only valid on asynchronous function types.
-  bool asyncFromAttr = false;
-  if (expr->getAttrs().hasAttribute<ConcurrentAttr>()) {
-    asyncFromAttr = true;
-  }
-
   auto throwFinder = FindInnerThrows(expr);
   body->walk(throwFinder);
   return ASTExtInfoBuilder()
       .withThrows(throwFinder.foundThrow(), /*FIXME:*/Type())
-      .withAsync(asyncFromAttr || bool(findAsyncNode(expr)))
+      .withAsync(bool(findAsyncNode(expr)))
       .withSendable(sendable)
       .build();
 }

lib/Sema/MiscDiagnostics.cpp

@@ -305,6 +305,11 @@ static void diagSyntacticUseRestrictions(const Expr *E, const DeclContext *DC,
         }
       }
 
+      // Performs checks on a closure.
+      if (auto *closure = dyn_cast<ClosureExpr>(E)) {
+        checkClosure(closure);
+      }
+
       // Specially diagnose some checked casts that are illegal.
       if (auto cast = dyn_cast<CheckedCastExpr>(E)) {
         checkCheckedCastExpr(cast);
@@ -1459,6 +1464,33 @@ static void diagSyntacticUseRestrictions(const Expr *E, const DeclContext *DC,
         }
       }
     }
+
+    void checkClosure(ClosureExpr *closure) {
+      if (closure->isImplicit()) {
+        return;
+      }
+
+      auto attr = closure->getAttrs().getAttribute<ConcurrentAttr>();
+      if (!attr) {
+        return;
+      }
+
+      if (closure->getAsyncLoc().isValid()) {
+        return;
+      }
+
+      if (closure->getType()->castTo<AnyFunctionType>()->isAsync()) {
+        return;
+      }
+
+      // `@concurrent` is not allowed on synchronous closures, but this is
+      // likely to change, so diagnose this here, post solution application,
+      // instead of introducing an "implies `async`" inference rule that won't
+      // make sense in the nearish future.
+      Ctx.Diags.diagnose(attr->getLocation(),
+                         diag::execution_behavior_only_on_async_closure, attr);
+      attr->setInvalid();
+    }
   };
 
   DiagnoseWalker Walker(DC, isExprStmt);

lib/Sema/TypeCheckAttr.cpp

@@ -8243,16 +8243,6 @@ public:
   }
 
   void checkExecutionBehaviorAttribute(DeclAttribute *attr) {
-    // execution behavior attribute implies `async`.
-    if (closure->hasExplicitResultType() &&
-        closure->getAsyncLoc().isInvalid()) {
-      ctx.Diags
-          .diagnose(attr->getLocation(),
-                    diag::execution_behavior_only_on_async_closure, attr)
-          .fixItRemove(attr->getRangeWithAt());
-      attr->setInvalid();
-    }
-
     if (auto actorType = getExplicitGlobalActor(closure)) {
       ctx.Diags
           .diagnose(