ff

Author: hamishknight

lib/Sema/PreCheckExpr.cpp

@@ -1345,33 +1345,35 @@ namespace {
 /// Perform prechecking of a ClosureExpr before we dive into it.  This returns
 /// true when we want the body to be considered part of this larger expression.
 bool PreCheckExpression::walkToClosureExprPre(ClosureExpr *closure) {
-  // If we won't be checking the body of the closure, don't walk into it here.
-  if (!closure->hasSingleExpressionBody()) {
-    if (LeaveClosureBodiesUnchecked)
-      return false;
-  }
-
-  // Update the current DeclContext to be the closure we're about to
-  // recurse into.
-  assert((closure->getParent() == DC ||
-          closure->getParent()->isChildContextOf(DC)) &&
-         "Decl context isn't correct");
-  DC = closure;
-
   // If we have a single statement that can become an expression, turn it
-  // into an expression now.
+  // into an expression now. This needs to happen before we check
+  // LeaveClosureBodiesUnchecked, as the closure may become a single expression
+  // closure.
   auto *body = closure->getBody();
   if (body->getNumElements() == 1) {
     if (auto *S = body->getLastElement().dyn_cast<Stmt *>()) {
       if (S->mayProduceSingleValue(Ctx)) {
         auto *SVE = SingleValueStmtExpr::createWithWrappedBranches(
-            Ctx, S, DC, /*mustBeExpr*/ false);
+            Ctx, S, /*DC*/ closure, /*mustBeExpr*/ false);
         auto *RS = new (Ctx) ReturnStmt(SourceLoc(), SVE);
         body->setLastElement(RS);
         closure->setBody(body, /*isSingleExpression*/ true);
       }
     }
   }
+
+  // If we won't be checking the body of the closure, don't walk into it here.
+  if (!closure->hasSingleExpressionBody()) {
+    if (LeaveClosureBodiesUnchecked)
+      return false;
+  }
+
+  // Update the current DeclContext to be the closure we're about to
+  // recurse into.
+  assert((closure->getParent() == DC ||
+          closure->getParent()->isChildContextOf(DC)) &&
+         "Decl context isn't correct");
+  DC = closure;
   return true;
 }