Perform OpaqueCast field projection on HIR, too.

This is necessary for closure captures in 2021 edition, as they capture individual fields, not the full mentioned variables. So it may try to capture a field of an opaque (because the hidden type is known to be something with a field).

2 files changed, 6 insertions, 0 deletions

diff --git a/compiler/rustc_middle/src/hir/place.rs b/compiler/rustc_middle/src/hir/place.rs
index 8a22de931c3..32f3a177508 100644
--- a/compiler/rustc_middle/src/hir/place.rs
+++ b/compiler/rustc_middle/src/hir/place.rs
@@ -36,6 +36,10 @@ pub enum ProjectionKind {
 
     /// A subslice covering a range of values like `B[x..y]`.
     Subslice,
+
+    /// A conversion from an opaque type to its hidden type so we can
+    /// do further projections on it.
+    OpaqueCast,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable)]
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index 91eefa2c125..6cf4fef1d04 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -174,6 +174,8 @@ impl<'tcx> CapturedPlace<'tcx> {
                 // Ignore derefs for now, as they are likely caused by
                 // autoderefs that don't appear in the original code.
                 HirProjectionKind::Deref => {}
+                // Just change the type to the hidden type, so we can actually project.
+                HirProjectionKind::OpaqueCast => {}
                 proj => bug!("Unexpected projection {:?} in captured place", proj),
             }
             ty = proj.ty;