Clean up leftovers from eager hidden type merging

6 files changed, 34 insertions, 109 deletions

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 3667d6bd640..6559ded5816 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -18,7 +18,9 @@ use rustc_index::vec::{Idx, IndexVec};
 use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::infer::{InferCtxt, LateBoundRegionConversionTime, NllRegionVariableOrigin};
+use rustc_infer::infer::{
+    InferCtxt, InferOk, LateBoundRegionConversionTime, NllRegionVariableOrigin,
+};
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::AssertKind;
@@ -194,31 +196,24 @@ pub(crate) fn type_check<'mir, 'tcx>(
             let opaque_type_values = opaque_type_values
                 .into_iter()
                 .filter_map(|(opaque_type_key, decl)| {
-                    let def_id = body.source.def_id().expect_local();
-                    let body_id = cx.tcx().hir().local_def_id_to_hir_id(def_id);
-                    let cause = ObligationCause::misc(body.span, body_id);
-                    let hidden = cx
-                        .fully_perform_op(
-                            Locations::All(body.span),
-                            ConstraintCategory::OpaqueType,
-                            CustomTypeOp::new(
-                                |infcx| {
-                                    let res = decl
-                                        .hidden_type(infcx, &cause, param_env)
-                                        .map_err(|e| e.0)?;
-                                    infcx.register_member_constraints(
-                                        param_env,
-                                        opaque_type_key,
-                                        res.value.ty,
-                                        res.value.span,
-                                    );
-                                    Ok(res)
-                                },
-                                || "opaque_type_map".to_string(),
-                            ),
-                        )
-                        .unwrap();
-                    let mut hidden_type = infcx.resolve_vars_if_possible(hidden.ty);
+                    cx.fully_perform_op(
+                        Locations::All(body.span),
+                        ConstraintCategory::OpaqueType,
+                        CustomTypeOp::new(
+                            |infcx| {
+                                infcx.register_member_constraints(
+                                    param_env,
+                                    opaque_type_key,
+                                    decl.hidden_type.ty,
+                                    decl.hidden_type.span,
+                                );
+                                Ok(InferOk { value: (), obligations: vec![] })
+                            },
+                            || "opaque_type_map".to_string(),
+                        ),
+                    )
+                    .unwrap();
+                    let mut hidden_type = infcx.resolve_vars_if_possible(decl.hidden_type.ty);
                     trace!(
                         "finalized opaque type {:?} to {:#?}",
                         opaque_type_key,
@@ -226,7 +221,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
                     );
                     if hidden_type.has_infer_types_or_consts() {
                         infcx.tcx.sess.delay_span_bug(
-                            hidden.span,
+                            decl.hidden_type.span,
                             &format!("could not resolve {:#?}", hidden_type.kind()),
                         );
                         hidden_type = infcx.tcx.ty_error();
@@ -263,7 +258,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
                         );
                         None
                     } else {
-                        Some((opaque_type_key, (hidden_type, hidden.span, decl.origin)))
+                        Some((opaque_type_key, (hidden_type, decl.hidden_type.span, decl.origin)))
                     }
                 })
                 .collect();
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index a86471affaa..18a1120051e 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -146,13 +146,13 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
         })
     }
 
-    fn take_opaque_types_for_query_response(&self) -> Vec<(OpaqueTypeKey<'tcx>, Vec<Ty<'tcx>>)> {
+    fn take_opaque_types_for_query_response(&self) -> Vec<(OpaqueTypeKey<'tcx>, Ty<'tcx>)> {
         self.inner
             .borrow_mut()
             .opaque_type_storage
             .take_opaque_types()
             .into_iter()
-            .map(|(k, v)| (k, v.hidden_types.into_iter().map(|ht| ht.ty).collect()))
+            .map(|(k, v)| (k, v.hidden_type.ty))
             .collect()
     }
 
@@ -497,14 +497,11 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
         let mut obligations = vec![];
 
         // Carry all newly resolved opaque types to the caller's scope
-        for (key, tys) in &query_response.value.opaque_types {
+        for &(key, ty) in &query_response.value.opaque_types {
             let substs = substitute_value(self.tcx, &result_subst, key.substs);
             let opaque = self.tcx.mk_opaque(key.def_id, substs);
-            for &ty in tys {
-                let ty = substitute_value(self.tcx, &result_subst, ty);
-                obligations
-                    .extend(self.handle_opaque_type(opaque, ty, cause, param_env)?.obligations);
-            }
+            let ty = substitute_value(self.tcx, &result_subst, ty);
+            obligations.extend(self.handle_opaque_type(opaque, ty, cause, param_env)?.obligations);
         }
 
         Ok(InferOk { value: result_subst, obligations })
diff --git a/compiler/rustc_infer/src/infer/opaque_types.rs b/compiler/rustc_infer/src/infer/opaque_types.rs
index cf57270df29..748fe1379cd 100644
--- a/compiler/rustc_infer/src/infer/opaque_types.rs
+++ b/compiler/rustc_infer/src/infer/opaque_types.rs
@@ -6,7 +6,6 @@ use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::vec_map::VecMap;
 use rustc_hir as hir;
 use rustc_middle::traits::ObligationCause;
-use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::subst::{GenericArgKind, Subst};
 use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable, TypeVisitor};
@@ -33,61 +32,12 @@ pub struct OpaqueTypeDecl<'tcx> {
     /// The hidden types that have been inferred for this opaque type.
     /// There can be multiple, but they are all `lub`ed together at the end
     /// to obtain the canonical hidden type.
-    pub hidden_types: Vec<OpaqueHiddenType<'tcx>>,
+    pub hidden_type: OpaqueHiddenType<'tcx>,
 
     /// The origin of the opaque type.
     pub origin: hir::OpaqueTyOrigin,
 }
 
-impl<'tcx> OpaqueTypeDecl<'tcx> {
-    pub fn hidden_type(
-        &self,
-        infcx: &InferCtxt<'_, 'tcx>,
-        cause: &ObligationCause<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-    ) -> Result<
-        InferOk<'tcx, OpaqueHiddenType<'tcx>>,
-        (TypeError<'tcx>, OpaqueHiddenType<'tcx>, OpaqueHiddenType<'tcx>),
-    > {
-        let mut value = self.hidden_types[0];
-        let mut obligations = vec![];
-        let mut error: Option<(_, _, OpaqueHiddenType<'tcx>)> = None;
-        for &next in self.hidden_types[1..].iter() {
-            // FIXME: make use of the spans to get nicer diagnostics!
-            let res = match infcx.at(cause, param_env).eq(value.ty, next.ty) {
-                Ok(res) => res,
-                Err(e) => {
-                    // Try to improve the span. Sometimes we have dummy spans, sometimes we are pointing
-                    // at an if/match instead of at the arm that gave us the type, but later spans point
-                    // to the right thing.
-                    if let Some((_, _, old)) = &mut error {
-                        old.span = old.span.substitute_dummy(next.span);
-                        // Shrink the span if possible
-                        if old.span.contains(next.span) {
-                            old.span = next.span;
-                        }
-                    } else {
-                        let mut next = next;
-                        next.span = next.span.substitute_dummy(cause.span(infcx.tcx));
-                        error = Some((e, value, next));
-                    }
-                    continue;
-                }
-            };
-            obligations.extend(res.obligations);
-            value.span = value.span.substitute_dummy(next.span);
-            // Shrink the span if possible
-            if value.span.contains(next.span) {
-                value.span = next.span;
-            }
-        }
-        match error {
-            None => Ok(InferOk { value, obligations }),
-            Some(e) => Err(e),
-        }
-    }
-}
-
 #[derive(Copy, Clone, Debug, TypeFoldable)]
 pub struct OpaqueHiddenType<'tcx> {
     /// The span of this particular definition of the opaque type. So
diff --git a/compiler/rustc_infer/src/infer/opaque_types/table.rs b/compiler/rustc_infer/src/infer/opaque_types/table.rs
index 1895c1a85c7..7f16a2f5332 100644
--- a/compiler/rustc_infer/src/infer/opaque_types/table.rs
+++ b/compiler/rustc_infer/src/infer/opaque_types/table.rs
@@ -20,7 +20,7 @@ impl<'tcx> OpaqueTypeStorage<'tcx> {
     #[instrument(level = "debug")]
     pub(crate) fn remove(&mut self, key: OpaqueTypeKey<'tcx>, idx: Option<OpaqueHiddenType<'tcx>>) {
         if let Some(idx) = idx {
-            self.opaque_types.get_mut(&key).unwrap().hidden_types[0] = idx;
+            self.opaque_types.get_mut(&key).unwrap().hidden_type = idx;
         } else {
             match self.opaque_types.remove(&key) {
                 None => bug!("reverted opaque type inference that was never registered: {:?}", key),
@@ -73,17 +73,15 @@ impl<'a, 'tcx> OpaqueTypeTable<'a, 'tcx> {
         &mut self,
         key: OpaqueTypeKey<'tcx>,
         opaque_type: Ty<'tcx>,
-        ty: OpaqueHiddenType<'tcx>,
+        hidden_type: OpaqueHiddenType<'tcx>,
         origin: OpaqueTyOrigin,
     ) -> Option<Ty<'tcx>> {
         if let Some(decl) = self.storage.opaque_types.get_mut(&key) {
-            assert_eq!(decl.hidden_types.len(), 1);
-            let prev = decl.hidden_types[0];
-            decl.hidden_types = vec![ty];
+            let prev = std::mem::replace(&mut decl.hidden_type, hidden_type);
             self.undo_log.push(UndoLog::OpaqueTypes(key, Some(prev)));
             return Some(prev.ty);
         }
-        let decl = OpaqueTypeDecl { opaque_type, hidden_types: vec![ty], origin };
+        let decl = OpaqueTypeDecl { opaque_type, hidden_type, origin };
         self.storage.opaque_types.insert(key, decl);
         self.undo_log.push(UndoLog::OpaqueTypes(key, None));
         None
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index cc83010580f..654ec022b60 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -180,7 +180,7 @@ pub struct QueryResponse<'tcx, R> {
     pub certainty: Certainty,
     /// List of opaque types for which we figured out a hidden type
     /// during the evaluation of the query.
-    pub opaque_types: Vec<(OpaqueTypeKey<'tcx>, Vec<Ty<'tcx>>)>,
+    pub opaque_types: Vec<(OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
     pub value: R,
 }
 
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index 5094806e75f..d4be3889a7a 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -99,8 +99,6 @@ pub use diverges::Diverges;
 pub use expectation::Expectation;
 pub use fn_ctxt::*;
 pub use inherited::{Inherited, InheritedBuilder};
-use rustc_infer::traits::ObligationCause;
-use traits::ObligationCauseCode::MiscObligation;
 
 use crate::astconv::AstConv;
 use crate::check::gather_locals::GatherLocalsVisitor;
@@ -474,19 +472,6 @@ fn typeck_with_fallback<'tcx>(
             fcx.require_type_is_sized(ty, span, code);
         }
 
-        let opaque_types = fcx.infcx.inner.borrow_mut().opaque_type_storage.opaque_types();
-        for (_, decl) in opaque_types {
-            let cause = ObligationCause::new(body.value.span, id, MiscObligation);
-            if let Err((err, expected, actual)) =
-                decl.hidden_type(&fcx.infcx, &cause, fcx.param_env)
-            {
-                let cause = ObligationCause::new(actual.span, id, MiscObligation);
-                fcx.report_mismatched_types(&cause, expected.ty, actual.ty, err)
-                    .span_label(expected.span, "type expected due to this")
-                    .emit();
-            }
-        }
-
         fcx.select_all_obligations_or_error();
 
         if fn_sig.is_some() {