Print to `stderr` when a graphviz file can't be written

`warn` prints nothing by default

diff --git a/compiler/rustc_mir/src/dataflow/framework/engine.rs b/compiler/rustc_mir/src/dataflow/framework/engine.rs
index d77e741d1a3ca62b6c90b90e4a50fa12b5b1f211..c1e500d01b1d34cb070d550ae820ad31be561c89 100644 (file)
--- a/compiler/rustc_mir/src/dataflow/framework/engine.rs
+++ b/compiler/rustc_mir/src/dataflow/framework/engine.rs
@@ -248,7 +248,7 @@ pub fn iterate_to_fixpoint(self) -> Results<'tcx, A>
 
         let res = write_graphviz_results(tcx, &body, &results, pass_name);
         if let Err(e) = res {
-            warn!("Failed to write graphviz dataflow results: {}", e);
+            error!("Failed to write graphviz dataflow results: {}", e);
         }
 
         results