Sema: Mark a PatternBindingDecl as implicit in the builder transform

Author: slavapestov

lib/Sema/BuilderTransform.cpp

@@ -1064,6 +1064,8 @@ class BuilderClosureRewriter
     auto pbd = PatternBindingDecl::create(
         ctx, SourceLoc(), StaticSpellingKind::None, temporaryVar->getLoc(),
         pattern, SourceLoc(), initExpr, dc);
+    if (temporaryVar->isImplicit())
+      pbd->setImplicit();
     elements.push_back(temporaryVar);
     elements.push_back(pbd);
   }