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).

6 files changed, 26 insertions, 0 deletions

diff --git a/compiler/rustc_hir_typeck/src/mem_categorization.rs b/compiler/rustc_hir_typeck/src/mem_categorization.rs
index 9de4f82a06b..e91103f2130 100644
--- a/compiler/rustc_hir_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_hir_typeck/src/mem_categorization.rs
@@ -457,7 +457,16 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
         ty: Ty<'tcx>,
         kind: ProjectionKind,
     ) -> PlaceWithHirId<'tcx> {
+        let place_ty = base_place.place.ty();
         let mut projections = base_place.place.projections;
+
+        let node_ty = self.typeck_results.node_type(node.hir_id());
+        // Opaque types can't have field projections, but we can instead convert
+        // the current place in-place (heh) to the hidden type, and then apply all
+        // follow up projections on that.
+        if node_ty != place_ty && place_ty.has_opaque_types() {
+            projections.push(Projection { kind: ProjectionKind::OpaqueCast, ty: node_ty });
+        }
         projections.push(Projection { kind, ty });
         PlaceWithHirId::new(
             node.hir_id(),
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index 62eff4bab86..facbb4b3cf8 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -673,6 +673,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     match (p1.kind, p2.kind) {
                         // Paths are the same, continue to next loop.
                         (ProjectionKind::Deref, ProjectionKind::Deref) => {}
+                        (ProjectionKind::OpaqueCast, ProjectionKind::OpaqueCast) => {}
                         (ProjectionKind::Field(i1, _), ProjectionKind::Field(i2, _))
                             if i1 == i2 => {}
 
@@ -695,10 +696,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             l @ (ProjectionKind::Index
                             | ProjectionKind::Subslice
                             | ProjectionKind::Deref
+                            | ProjectionKind::OpaqueCast
                             | ProjectionKind::Field(..)),
                             r @ (ProjectionKind::Index
                             | ProjectionKind::Subslice
                             | ProjectionKind::Deref
+                            | ProjectionKind::OpaqueCast
                             | ProjectionKind::Field(..)),
                         ) => bug!(
                             "ProjectionKinds Index or Subslice were unexpected: ({:?}, {:?})",
@@ -1885,6 +1888,7 @@ fn restrict_capture_precision(
                 return (place, curr_mode);
             }
             ProjectionKind::Deref => {}
+            ProjectionKind::OpaqueCast => {}
             ProjectionKind::Field(..) => {} // ignore
         }
     }
@@ -1941,6 +1945,7 @@ fn construct_place_string<'tcx>(tcx: TyCtxt<'_>, place: &Place<'tcx>) -> String
             ProjectionKind::Deref => String::from("Deref"),
             ProjectionKind::Index => String::from("Index"),
             ProjectionKind::Subslice => String::from("Subslice"),
+            ProjectionKind::OpaqueCast => String::from("OpaqueCast"),
         };
         if i != 0 {
             projections_str.push(',');
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;
diff --git a/compiler/rustc_mir_build/src/build/expr/as_place.rs b/compiler/rustc_mir_build/src/build/expr/as_place.rs
index 7756d5d4879..2e7ef265a93 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_place.rs
@@ -236,6 +236,9 @@ fn strip_prefix<'a, 'tcx>(
                 }
                 assert_matches!(iter.next(), Some(ProjectionElem::Field(..)));
             }
+            HirProjectionKind::OpaqueCast => {
+                assert_matches!(iter.next(), Some(ProjectionElem::OpaqueCast(..)));
+            }
             HirProjectionKind::Index | HirProjectionKind::Subslice => {
                 bug!("unexpected projection kind: {:?}", projection);
             }
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index 711a9126c04..2f0f71a8dc6 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -1074,6 +1074,9 @@ impl<'tcx> Cx<'tcx> {
                     variant_index,
                     name: field,
                 },
+                HirProjectionKind::OpaqueCast => {
+                    ExprKind::Use { source: self.thir.exprs.push(captured_place_expr) }
+                }
                 HirProjectionKind::Index | HirProjectionKind::Subslice => {
                     // We don't capture these projections, so we can ignore them here
                     continue;