Provide a better diagnostic on failure to meet send bound on futures in a foreign crate

Adding diagnostic data on generators to the crate metadata and using it to provide
a better diagnostic on failure to meet send bound on futures originated from a foreign crate

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -28,6 +28,7 @@ use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
 use rustc_middle::thir;
 use rustc_middle::ty::codec::TyDecoder;
 use rustc_middle::ty::fast_reject::SimplifiedType;
+use rustc_middle::ty::GeneratorDiagnosticData;
 use rustc_middle::ty::{self, Ty, TyCtxt, Visibility};
 use rustc_serialize::{opaque, Decodable, Decoder};
 use rustc_session::cstore::{
@@ -1732,6 +1733,24 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
                 .collect()
         })
     }
+
+    fn get_generator_diagnostic_data(
+        self,
+        tcx: TyCtxt<'tcx>,
+        id: DefIndex,
+    ) -> Option<GeneratorDiagnosticData<'tcx>> {
+        self.root
+            .tables
+            .generator_diagnostic_data
+            .get(self, id)
+            .map(|param| param.decode((self, tcx)))
+            .map(|generator_data| GeneratorDiagnosticData {
+                generator_interior_types: generator_data.generator_interior_types,
+                hir_owner: generator_data.hir_owner,
+                nodes_types: generator_data.nodes_types,
+                adjustments: generator_data.adjustments,
+            })
+    }
 }
 
 impl CrateMetadata {

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -246,6 +246,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
 
     crate_extern_paths => { cdata.source().paths().cloned().collect() }
     expn_that_defined => { cdata.get_expn_that_defined(def_id.index, tcx.sess) }
+    generator_diagnostic_data => { cdata.get_generator_diagnostic_data(tcx, def_id.index) }
 }
 
 pub(in crate::rmeta) fn provide(providers: &mut Providers) {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1550,16 +1550,17 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
     fn encode_info_for_closure(&mut self, hir_id: hir::HirId) {
         let def_id = self.tcx.hir().local_def_id(hir_id);
         debug!("EncodeContext::encode_info_for_closure({:?})", def_id);
-
         // NOTE(eddyb) `tcx.type_of(def_id)` isn't used because it's fully generic,
         // including on the signature, which is inferred in `typeck.
-        let ty = self.tcx.typeck(def_id).node_type(hir_id);
-
+        let typeck_result: &'tcx ty::TypeckResults<'tcx> = self.tcx.typeck(def_id);
+        let ty = typeck_result.node_type(hir_id);
         match ty.kind() {
             ty::Generator(..) => {
                 let data = self.tcx.generator_kind(def_id).unwrap();
+                let generator_diagnostic_data = typeck_result.get_generator_diagnostic_data();
                 record!(self.tables.kind[def_id.to_def_id()] <- EntryKind::Generator);
                 record!(self.tables.generator_kind[def_id.to_def_id()] <- data);
+                record!(self.tables.generator_diagnostic_data[def_id.to_def_id()]  <- generator_diagnostic_data);
             }
 
             ty::Closure(..) => {

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -19,6 +19,7 @@ use rustc_middle::mir;
 use rustc_middle::thir;
 use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::query::Providers;
+use rustc_middle::ty::GeneratorDiagnosticData;
 use rustc_middle::ty::{self, ReprOptions, Ty};
 use rustc_serialize::opaque::Encoder;
 use rustc_session::config::SymbolManglingVersion;
@@ -358,6 +359,7 @@ define_tables! {
     def_keys: Table<DefIndex, Lazy<DefKey>>,
     def_path_hashes: Table<DefIndex, DefPathHash>,
     proc_macro_quoted_spans: Table<usize, Lazy<Span>>,
+    generator_diagnostic_data: Table<DefIndex, Lazy<GeneratorDiagnosticData<'tcx>>>,
 }
 
 #[derive(Copy, Clone, MetadataEncodable, MetadataDecodable)]