Use `eq_opaque_type_and_type` when type-checking closure signatures

[rust.git] / src / librustc_mir / borrow_check / nll / type_check / input_output.rs

diff --git a/src/librustc_mir/borrow_check/nll/type_check/input_output.rs b/src/librustc_mir/borrow_check/nll/type_check/input_output.rs
index 3954d62ad5c77e4f241e1ec9d5cb0f84f8203cbd..35fb677c053cb99ae7d5955be1144fb8d2b5e739 100644 (file)
--- a/src/librustc_mir/borrow_check/nll/type_check/input_output.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/input_output.rs
@@ -1,7 +1,7 @@
 //! This module contains code to equate the input/output types appearing
 //! in the MIR with the expected input/output types from the function
 //! signature. This requires a bit of processing, as the expected types
-//! are supplied to us before normalization and may contain existential
+//! are supplied to us before normalization and may contain opaque
 //! `impl Trait` instances. In contrast, the input/output types found in
 //! the MIR (specifically, in the special local variables for the
 //! `RETURN_PLACE` the MIR arguments) are always fully normalized (and
@@ -12,7 +12,7 @@
 use rustc::mir::*;
 use rustc::ty::Ty;
 
-use rustc_data_structures::indexed_vec::Idx;
+use rustc_index::vec::Idx;
 use syntax_pos::Span;
 
 use super::{Locations, TypeChecker};
@@ -113,8 +113,7 @@ pub(super) fn equate_inputs_and_outputs(
             self.equate_normalized_input_or_output(ur_yield_ty, mir_yield_ty, yield_span);
         }
 
-        // Return types are a bit more complex. They may contain existential `impl Trait`
-        // types.
+        // Return types are a bit more complex. They may contain opaque `impl Trait` types.
         let mir_output_ty = body.local_decls[RETURN_PLACE].ty;
         let output_span = body.local_decls[RETURN_PLACE].source_info.span;
         if let Err(terr) = self.eq_opaque_type_and_type(
@@ -135,15 +134,27 @@ pub(super) fn equate_inputs_and_outputs(
         };
 
         // If the user explicitly annotated the output types, enforce those.
+        // Note that this only happens for closures.
         if let Some(user_provided_sig) = user_provided_sig {
             let user_provided_output_ty = user_provided_sig.output();
             let user_provided_output_ty =
                 self.normalize(user_provided_output_ty, Locations::All(output_span));
-            self.equate_normalized_input_or_output(
-                user_provided_output_ty,
+            if let Err(err) = self.eq_opaque_type_and_type(
                 mir_output_ty,
-                output_span,
-            );
+                user_provided_output_ty,
+                self.mir_def_id,
+                Locations::All(output_span),
+                ConstraintCategory::BoringNoLocation
+            ) {
+                span_mirbug!(
+                    self,
+                    Location::START,
+                    "equate_inputs_and_outputs: `{:?}=={:?}` failed with `{:?}`",
+                    mir_output_ty,
+                    user_provided_output_ty,
+                    err
+                );
+            }
         }
     }