Call FileEncoder::finish in rmeta encoding

compiler/rustc_incremental/src/persist/save.rs

@@ -49,7 +49,7 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
         join(
             move || {
                 sess.time("incr_comp_persist_dep_graph", || {
-                    if let Err(err) = tcx.dep_graph.encode(&tcx.sess.prof) {
+                    if let Err(err) = tcx.dep_graph.finish_encoding(&tcx.sess.prof) {
                         sess.emit_err(errors::WriteDepGraph { path: &staging_dep_graph_path, err });
                     }
                     if let Err(err) = fs::rename(&staging_dep_graph_path, &dep_graph_path) {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2251,7 +2251,12 @@ fn encode_metadata_impl(tcx: TyCtxt<'_>, path: &Path) {
     // culminating in the `CrateRoot` which points to all of it.
     let root = ecx.encode_crate_root();
 
-    ecx.opaque.flush();
+    // Make sure we report any errors from writing to the file.
+    // If we forget this, compilation can succeed with an incomplete rmeta file,
+    // causing an ICE when the rmeta file is read by another compilation.
+    if let Err(err) = ecx.opaque.finish() {
+        tcx.sess.emit_err(FailWriteFile { err });
+    }
 
     let mut file = ecx.opaque.file();
     // We will return to this position after writing the root position.

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -867,7 +867,7 @@ impl<'a, 'tcx> CacheEncoder<'a, 'tcx> {
     }
 
     #[inline]
-    fn finish(self) -> Result<usize, io::Error> {
+    fn finish(mut self) -> Result<usize, io::Error> {
         self.encoder.finish()
     }
 }

compiler/rustc_query_system/src/dep_graph/graph.rs

@@ -989,7 +989,7 @@ impl<D: Deps> DepGraph<D> {
         }
     }
 
-    pub fn encode(&self, profiler: &SelfProfilerRef) -> FileEncodeResult {
+    pub fn finish_encoding(&self, profiler: &SelfProfilerRef) -> FileEncodeResult {
         if let Some(data) = &self.data {
             data.current.encoder.steal().finish(profiler)
         } else {

compiler/rustc_serialize/src/opaque.rs

@@ -152,7 +152,7 @@ impl FileEncoder {
         })
     }
 
-    pub fn finish(mut self) -> Result<usize, io::Error> {
+    pub fn finish(&mut self) -> Result<usize, io::Error> {
         self.flush();
         match std::mem::replace(&mut self.res, Ok(())) {
             Ok(()) => Ok(self.position()),