[IRGenDebugInfo] Enable an assertion.

Author: Davide Italiano

lib/IRGen/IRGenDebugInfo.cpp

@@ -2141,10 +2141,7 @@ void IRGenDebugInfoImpl::emitVariableDeclaration(
     IRBuilder &Builder, ArrayRef<llvm::Value *> Storage, DebugTypeInfo DbgTy,
     const SILDebugScope *DS, ValueDecl *VarDecl, StringRef Name, unsigned ArgNo,
     IndirectionKind Indirection, ArtificialKind Artificial) {
-  // FIXME: Make this an assertion.
-  // assert(DS && "variable has no scope");
-  if (!DS)
-    return;
+  assert(DS && "variable has no scope");
 
   if (Opts.DebugInfoLevel <= IRGenDebugInfoLevel::LineTables)
     return;