store the `HirId` of the upvar

src/librustc/ich/impls_mir.rs

@@ -30,7 +30,7 @@
     internal,
     is_user_variable
 });
-impl_stable_hash_for!(struct mir::UpvarDecl { debug_name, by_ref, mutability });
+impl_stable_hash_for!(struct mir::UpvarDecl { debug_name, var_hir_id, by_ref, mutability });
 impl_stable_hash_for!(struct mir::BasicBlockData<'tcx> { statements, terminator, is_cleanup });
 impl_stable_hash_for!(struct mir::UnsafetyViolation { source_info, description, kind });
 impl_stable_hash_for!(struct mir::UnsafetyCheckResult { violations, unsafe_blocks });

src/librustc/mir/mod.rs

@@ -15,7 +15,7 @@
 use graphviz::IntoCow;
 use hir::def::CtorKind;
 use hir::def_id::DefId;
-use hir::{self, InlineAsm};
+use hir::{self, HirId, InlineAsm};
 use middle::region;
 use mir::interpret::{EvalErrorKind, Scalar, Value};
 use mir::visit::MirVisitable;
@@ -785,6 +785,9 @@ pub fn new_return_place(return_ty: Ty, span: Span) -> LocalDecl {
 pub struct UpvarDecl {
     pub debug_name: Name,
 
+    /// `HirId` of the captured variable
+    pub var_hir_id: ClearCrossCrate<HirId>,
+
     /// If true, the capture is behind a reference.
     pub by_ref: bool,
 

src/librustc_mir/build/mod.rs

@@ -534,6 +534,7 @@ fn construct_fn<'a, 'gcx, 'tcx, A>(hir: Cx<'a, 'gcx, 'tcx>,
             };
             let mut decl = UpvarDecl {
                 debug_name: keywords::Invalid.name(),
+                var_hir_id: ClearCrossCrate::Set(var_hir_id),
                 by_ref,
                 mutability: Mutability::Not,
             };