Rollup merge of #116879 - aliemjay:revert-opaque-bubble, r=oli-obk

revert #114586

Reverts #114586.

cc #116877 (not closing until this gets a beta backport)
fixes #116684
fixes https://github.com/rust-lang/rust/pull/114586#issuecomment-1751967321

r? `@oli-obk` or `@lcnr`

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -328,26 +328,19 @@ fn check_opaque_type_well_formed<'tcx>(
 
     // Require that the hidden type actually fulfills all the bounds of the opaque type, even without
     // the bounds that the function supplies.
-    let mut obligations = vec![];
+    let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), identity_args);
-    infcx
+    ocx.eq(&ObligationCause::misc(definition_span, def_id), param_env, opaque_ty, definition_ty)
-        .insert_hidden_type(
+        .map_err(|err| {
-            OpaqueTypeKey { def_id, args: identity_args },
+            infcx
-            &ObligationCause::misc(definition_span, def_id),
+                .err_ctxt()
-            param_env,
+                .report_mismatched_types(
-            definition_ty,
+                    &ObligationCause::misc(definition_span, def_id),
-            true,
+                    opaque_ty,
-            &mut obligations,
+                    definition_ty,
-        )
+                    err,
-        .unwrap();
+                )
-    infcx.add_item_bounds_for_hidden_type(
+                .emit()
-        def_id.to_def_id(),
+        })?;
-        identity_args,
-        ObligationCause::misc(definition_span, def_id),
-        param_env,
-        definition_ty,
-        &mut obligations,
-    );
-    ocx.register_obligations(obligations);
 
     // Require the hidden type to be well-formed with only the generics of the opaque type.
     // Defining use functions may have more bounds than the opaque type, which is ok, as long as the

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -145,25 +145,7 @@ impl<'tcx> InferCtxt<'tcx> {
                             return None;
                         }
                     }
-                    DefiningAnchor::Bubble => {
+                    DefiningAnchor::Bubble => {}
-                        if let ty::Alias(ty::Opaque, _) = b.kind() {
-                            // In bubble mode we don't know which of the two opaque types is supposed to have the other
-                            // as a hidden type (both, none or either one of them could be in its defining scope).
-                            let predicate = ty::PredicateKind::AliasRelate(
-                                a.into(),
-                                b.into(),
-                                ty::AliasRelationDirection::Equate,
-                            );
-                            let obligation = traits::Obligation::new(
-                                self.tcx,
-                                cause.clone(),
-                                param_env,
-                                predicate,
-                            );
-                            let obligations = vec![obligation];
-                            return Some(Ok(InferOk { value: (), obligations }));
-                        }
-                    }
                     DefiningAnchor::Error => return None,
                 };
                 if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, .. }) = *b.kind() {

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -6,7 +6,6 @@ use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::traits::ProjectionCacheKey;
 use rustc_infer::traits::{PolyTraitObligation, SelectionError, TraitEngine};
 use rustc_middle::mir::interpret::ErrorHandled;
-use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::GenericArgsRef;
@@ -626,27 +625,9 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
                     }
                 }
                 ty::PredicateKind::Ambiguous => ProcessResult::Unchanged,
-                ty::PredicateKind::AliasRelate(..)
+                ty::PredicateKind::AliasRelate(..) => {
-                    if matches!(self.selcx.infcx.defining_use_anchor, DefiningAnchor::Bubble) =>
+                    bug!("AliasRelate is only used for new solver")
-                {
-                    ProcessResult::Unchanged
                 }
-                ty::PredicateKind::AliasRelate(a, b, relate) => match relate {
-                    ty::AliasRelationDirection::Equate => match self
-                        .selcx
-                        .infcx
-                        .at(&obligation.cause, obligation.param_env)
-                        .eq(DefineOpaqueTypes::Yes, a, b)
-                    {
-                        Ok(inf_ok) => ProcessResult::Changed(mk_pending(inf_ok.into_obligations())),
-                        Err(_) => ProcessResult::Error(FulfillmentErrorCode::CodeSelectionError(
-                            SelectionError::Unimplemented,
-                        )),
-                    },
-                    ty::AliasRelationDirection::Subtype => {
-                        bug!("AliasRelate with subtyping is only used for new solver")
-                    }
-                },
                 ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
                     match self.selcx.infcx.at(&obligation.cause, obligation.param_env).eq(
                         DefineOpaqueTypes::No,

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -38,7 +38,6 @@ use rustc_infer::traits::TraitObligation;
 use rustc_middle::dep_graph::dep_kinds;
 use rustc_middle::dep_graph::DepNodeIndex;
 use rustc_middle::mir::interpret::ErrorHandled;
-use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::_match::MatchAgainstFreshVars;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::fold::BottomUpFolder;
@@ -1005,27 +1004,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                         }
                     }
                 }
-                ty::PredicateKind::AliasRelate(..)
+                ty::PredicateKind::AliasRelate(..) => {
-                    if matches!(self.infcx.defining_use_anchor, DefiningAnchor::Bubble) =>
+                    bug!("AliasRelate is only used for new solver")
-                {
-                    Ok(EvaluatedToAmbig)
                 }
-                ty::PredicateKind::AliasRelate(a, b, relate) => match relate {
-                    ty::AliasRelationDirection::Equate => match self
-                        .infcx
-                        .at(&obligation.cause, obligation.param_env)
-                        .eq(DefineOpaqueTypes::Yes, a, b)
-                    {
-                        Ok(inf_ok) => self.evaluate_predicates_recursively(
-                            previous_stack,
-                            inf_ok.into_obligations(),
-                        ),
-                        Err(_) => Ok(EvaluatedToErr),
-                    },
-                    ty::AliasRelationDirection::Subtype => {
-                        bug!("AliasRelate subtyping is only used for new solver")
-                    }
-                },
                 ty::PredicateKind::Ambiguous => Ok(EvaluatedToAmbig),
                 ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(ct, ty)) => {
                     match self.infcx.at(&obligation.cause, obligation.param_env).eq(

tests/ui/impl-trait/equality-in-canonical-query.clone.stderr

@@ -0,0 +1,29 @@
+error: internal compiler error: no errors encountered even though `delay_span_bug` issued
+
+error: internal compiler error: {OpaqueTypeKey { def_id: DefId(rpit::{opaque#0}), args: [] }: OpaqueTypeDecl { hidden_type: OpaqueHiddenType { span: no-location (#0), ty: Alias(Opaque, AliasTy { args: [], def_id: DefId(foo::{opaque#0}) }) } }}
+   |
+   = 
+           
+
+error: internal compiler error: error performing ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing }, value: ProvePredicate { predicate: Binder { value: ProjectionPredicate(AliasTy { args: [FnDef(DefId(rpit), []), ()], def_id: DefId(ops::function::FnOnce::Output) }, Term::Ty(Alias(Opaque, AliasTy { args: [], def_id: DefId(foo::{opaque#0}) }))), bound_vars: [] } } }
+  --> $DIR/equality-in-canonical-query.rs:19:5
+   |
+LL |     same_output(foo, rpit);
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |
+
+  --> $DIR/equality-in-canonical-query.rs:19:5
+   |
+LL |     same_output(foo, rpit);
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+
+
+
+
+
+
+query stack during panic:
+end of query stack
+error: aborting due to 3 previous errors
+

tests/ui/impl-trait/equality-in-canonical-query.rs

@@ -0,0 +1,23 @@
+// issue: #116877
+// revisions: sized clone
+//[sized] check-pass
+
+//[clone] known-bug: #108498
+//[clone] failure-status: 101
+//[clone] normalize-stderr-test: "DefId\(.*?\]::" -> "DefId("
+//[clone] normalize-stderr-test: "(?m)note: .*$" -> ""
+//[clone] normalize-stderr-test: "(?m)^ *\d+: .*\n" -> ""
+//[clone] normalize-stderr-test: "(?m)^ *at .*\n" -> ""
+
+#[cfg(sized)] fn rpit() -> impl Sized {}
+#[cfg(clone)] fn rpit() -> impl Clone {}
+
+fn same_output<Out>(_: impl Fn() -> Out, _: impl Fn() -> Out) {}
+
+pub fn foo() -> impl Sized {
+    same_output(rpit, foo);
+    same_output(foo, rpit);
+    rpit()
+}
+
+fn main () {}

tests/ui/type-alias-impl-trait/rpit_tait_equality_in_canonical_query.current.stderr

@@ -1,11 +1,17 @@
 error: internal compiler error: no errors encountered even though `delay_span_bug` issued
 
-error: internal compiler error: ambiguity performing ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing }, value: ProvePredicate { predicate: Binder { value: ProjectionPredicate(AliasTy { args: [FnDef(DefId(get_rpit), []), ()], def_id: DefId(ops::function::FnOnce::Output) }, Term::Ty(Alias(Opaque, AliasTy { args: [], def_id: DefId(Opaque::{opaque#0}) }))), bound_vars: [] } } }
+error: internal compiler error: {OpaqueTypeKey { def_id: DefId(get_rpit::{opaque#0}), args: [] }: OpaqueTypeDecl { hidden_type: OpaqueHiddenType { span: no-location (#0), ty: Alias(Opaque, AliasTy { args: [], def_id: DefId(Opaque::{opaque#0}) }) } }}
+   |
+   = 
+           
+
+error: internal compiler error: error performing ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing }, value: ProvePredicate { predicate: Binder { value: ProjectionPredicate(AliasTy { args: [FnDef(DefId(get_rpit), []), ()], def_id: DefId(ops::function::FnOnce::Output) }, Term::Ty(Alias(Opaque, AliasTy { args: [], def_id: DefId(Opaque::{opaque#0}) }))), bound_vars: [] } } }
   --> $DIR/rpit_tait_equality_in_canonical_query.rs:28:5
    |
 LL |     query(get_rpit);
    |     ^^^^^^^^^^^^^^^
    |
+
   --> $DIR/rpit_tait_equality_in_canonical_query.rs:28:5
    |
 LL |     query(get_rpit);
@@ -14,7 +20,10 @@ LL |     query(get_rpit);
 
 
 
+
+
+
 query stack during panic:
 end of query stack
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/type-alias-impl-trait/rpit_tait_equality_in_canonical_query.rs

@@ -12,7 +12,7 @@
 //[current] known-bug: #108498
 //[current] failure-status: 101
 //[current] normalize-stderr-test: "DefId\(.*?\]::" -> "DefId("
-//[current] normalize-stderr-test: "(?m)^note: .*\n" -> ""
+//[current] normalize-stderr-test: "(?m)note: .*$" -> ""
 //[current] normalize-stderr-test: "(?m)^ *\d+: .*\n" -> ""
 //[current] normalize-stderr-test: "(?m)^ *at .*\n" -> ""
 

tests/ui/type-alias-impl-trait/rpit_tait_equality_in_canonical_query_2.rs

@@ -0,0 +1,18 @@
+// The canonical query `Projection(<get_rpit as FnOnce>::Output = Opaque)`
+// is the *only* site that defines `Opaque` in MIR typeck.
+//
+// check-pass
+
+#![feature(type_alias_impl_trait)]
+
+type Opaque = impl Sized;
+
+fn get_rpit() -> impl Sized {}
+
+fn query(_: impl FnOnce() -> Opaque) {}
+
+fn test(_: Opaque) {
+    query(get_rpit);
+}
+
+fn main() {}