Rollup merge of rust-lang#104926 - spastorino:calculate_diverging_fallback-cleanups, r=lcnr

Move relationships from FulfillmentContext to Inherited

r? `@lcnr`

Author: Dylan-DPC

compiler/rustc_hir_typeck/src/fallback.rs

@@ -196,8 +196,6 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
     ) -> FxHashMap<Ty<'tcx>, Ty<'tcx>> {
         debug!("calculate_diverging_fallback({:?})", unsolved_variables);
 
-        let relationships = self.fulfillment_cx.borrow_mut().relationships().clone();
-
         // Construct a coercion graph where an edge `A -> B` indicates
         // a type variable is that is coerced
         let coercion_graph = self.create_coercion_graph();
@@ -281,9 +279,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
             roots_reachable_from_non_diverging,
         );
 
-        debug!("inherited: {:#?}", self.inh.fulfillment_cx.borrow_mut().pending_obligations());
         debug!("obligations: {:#?}", self.fulfillment_cx.borrow_mut().pending_obligations());
-        debug!("relationships: {:#?}", relationships);
 
         // For each diverging variable, figure out whether it can
         // reach a member of N. If so, it falls back to `()`. Else
@@ -297,16 +293,16 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
                 .depth_first_search(root_vid)
                 .any(|n| roots_reachable_from_non_diverging.visited(n));
 
-            let mut relationship = ty::FoundRelationships { self_in_trait: false, output: false };
+            let mut found_infer_var_info = ty::InferVarInfo { self_in_trait: false, output: false };
 
-            for (vid, rel) in relationships.iter() {
-                if self.root_var(*vid) == root_vid {
-                    relationship.self_in_trait |= rel.self_in_trait;
-                    relationship.output |= rel.output;
+            for (vid, info) in self.inh.infer_var_info.borrow().iter() {
+                if self.infcx.root_var(*vid) == root_vid {
+                    found_infer_var_info.self_in_trait |= info.self_in_trait;
+                    found_infer_var_info.output |= info.output;
                 }
             }
 
-            if relationship.self_in_trait && relationship.output {
+            if found_infer_var_info.self_in_trait && found_infer_var_info.output {
                 // This case falls back to () to ensure that the code pattern in
                 // tests/ui/never_type/fallback-closure-ret.rs continues to
                 // compile when never_type_fallback is enabled.

compiler/rustc_hir_typeck/src/inherited.rs

@@ -1,6 +1,6 @@
 use super::callee::DeferredCallResolution;
 
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::HirIdMap;
@@ -10,7 +10,8 @@ use rustc_middle::ty::visit::TypeVisitable;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::def_id::LocalDefIdMap;
 use rustc_span::{self, Span};
-use rustc_trait_selection::traits::{self, TraitEngine, TraitEngineExt as _};
+use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
+use rustc_trait_selection::traits::{self, PredicateObligation, TraitEngine, TraitEngineExt as _};
 
 use std::cell::RefCell;
 use std::ops::Deref;
@@ -63,6 +64,8 @@ pub struct Inherited<'tcx> {
     /// we record that type variable here. This is later used to inform
     /// fallback. See the `fallback` module for details.
     pub(super) diverging_type_vars: RefCell<FxHashSet<Ty<'tcx>>>,
+
+    pub(super) infer_var_info: RefCell<FxHashMap<ty::TyVid, ty::InferVarInfo>>,
 }
 
 impl<'tcx> Deref for Inherited<'tcx> {
@@ -128,6 +131,7 @@ impl<'tcx> Inherited<'tcx> {
             deferred_generator_interiors: RefCell::new(Vec::new()),
             diverging_type_vars: RefCell::new(Default::default()),
             body_id,
+            infer_var_info: RefCell::new(Default::default()),
         }
     }
 
@@ -136,6 +140,9 @@ impl<'tcx> Inherited<'tcx> {
         if obligation.has_escaping_bound_vars() {
             span_bug!(obligation.cause.span, "escaping bound vars in predicate {:?}", obligation);
         }
+
+        self.update_infer_var_info(&obligation);
+
         self.fulfillment_cx.borrow_mut().register_predicate_obligation(self, obligation);
     }
 
@@ -152,4 +159,43 @@ impl<'tcx> Inherited<'tcx> {
         self.register_predicates(infer_ok.obligations);
         infer_ok.value
     }
+
+    pub fn update_infer_var_info(&self, obligation: &PredicateObligation<'tcx>) {
+        let infer_var_info = &mut self.infer_var_info.borrow_mut();
+
+        // (*) binder skipped
+        if let ty::PredicateKind::Clause(ty::Clause::Trait(tpred)) = obligation.predicate.kind().skip_binder()
+            && let Some(ty) = self.shallow_resolve(tpred.self_ty()).ty_vid().map(|t| self.root_var(t))
+            && self.tcx.lang_items().sized_trait().map_or(false, |st| st != tpred.trait_ref.def_id)
+        {
+            let new_self_ty = self.tcx.types.unit;
+
+            // Then construct a new obligation with Self = () added
+            // to the ParamEnv, and see if it holds.
+            let o = obligation.with(self.tcx,
+                obligation
+                    .predicate
+                    .kind()
+                    .rebind(
+                        // (*) binder moved here
+                        ty::PredicateKind::Clause(ty::Clause::Trait(tpred.with_self_ty(self.tcx, new_self_ty)))
+                    ),
+            );
+            // Don't report overflow errors. Otherwise equivalent to may_hold.
+            if let Ok(result) = self.probe(|_| self.evaluate_obligation(&o)) && result.may_apply() {
+                infer_var_info.entry(ty).or_default().self_in_trait = true;
+            }
+        }
+
+        if let ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) =
+            obligation.predicate.kind().skip_binder()
+        {
+            // If the projection predicate (Foo::Bar == X) has X as a non-TyVid,
+            // we need to make it into one.
+            if let Some(vid) = predicate.term.ty().and_then(|ty| ty.ty_vid()) {
+                debug!("infer_var_info: {:?}.output = true", vid);
+                infer_var_info.entry(vid).or_default().output = true;
+            }
+        }
+    }
 }

compiler/rustc_infer/src/traits/engine.rs

@@ -1,6 +1,5 @@
 use crate::infer::InferCtxt;
 use crate::traits::Obligation;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::{self, ToPredicate, Ty};
 
@@ -42,8 +41,6 @@ pub trait TraitEngine<'tcx>: 'tcx {
     fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>>;
 
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>>;
-
-    fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships>;
 }
 
 pub trait TraitEngineExt<'tcx> {

compiler/rustc_middle/src/ty/mod.rs

@@ -2619,7 +2619,7 @@ impl<'tcx> fmt::Debug for SymbolName<'tcx> {
 }
 
 #[derive(Debug, Default, Copy, Clone)]
-pub struct FoundRelationships {
+pub struct InferVarInfo {
     /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
     /// obligation, where:
     ///

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -1,14 +1,12 @@
 use std::mem;
 
-use rustc_data_structures::fx::FxHashMap;
 use rustc_infer::{
     infer::InferCtxt,
     traits::{
         query::NoSolution, FulfillmentError, FulfillmentErrorCode, PredicateObligation,
         SelectionError, TraitEngine,
     },
 };
-use rustc_middle::ty;
 
 use super::{search_graph, Certainty, EvalCtxt};
 
@@ -102,8 +100,4 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
         self.obligations.clone()
     }
-
-    fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships> {
-        unimplemented!("Should be moved out of `TraitEngine`")
-    }
 }

compiler/rustc_trait_selection/src/traits/chalk_fulfill.rs

@@ -7,24 +7,18 @@ use crate::traits::{
     ChalkEnvironmentAndGoal, FulfillmentError, FulfillmentErrorCode, PredicateObligation,
     SelectionError, TraitEngine,
 };
-use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
-use rustc_middle::ty::{self, TypeVisitable};
+use rustc_data_structures::fx::FxIndexSet;
+use rustc_middle::ty::TypeVisitable;
 
 pub struct FulfillmentContext<'tcx> {
     obligations: FxIndexSet<PredicateObligation<'tcx>>,
 
-    relationships: FxHashMap<ty::TyVid, ty::FoundRelationships>,
-
     usable_in_snapshot: bool,
 }
 
 impl FulfillmentContext<'_> {
     pub(super) fn new() -> Self {
-        FulfillmentContext {
-            obligations: FxIndexSet::default(),
-            relationships: FxHashMap::default(),
-            usable_in_snapshot: false,
-        }
+        FulfillmentContext { obligations: FxIndexSet::default(), usable_in_snapshot: false }
     }
 
     pub(crate) fn new_in_snapshot() -> Self {
@@ -43,8 +37,6 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
         }
         let obligation = infcx.resolve_vars_if_possible(obligation);
 
-        super::relationships::update(self, infcx, &obligation);
-
         self.obligations.insert(obligation);
     }
 
@@ -154,8 +146,4 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
         self.obligations.iter().cloned().collect()
     }
-
-    fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships> {
-        &mut self.relationships
-    }
 }

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -1,5 +1,4 @@
 use crate::infer::{InferCtxt, TyOrConstInferVar};
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::obligation_forest::ProcessResult;
 use rustc_data_structures::obligation_forest::{Error, ForestObligation, Outcome};
 use rustc_data_structures::obligation_forest::{ObligationForest, ObligationProcessor};
@@ -54,8 +53,6 @@ pub struct FulfillmentContext<'tcx> {
     // fulfillment context.
     predicates: ObligationForest<PendingPredicateObligation<'tcx>>,
 
-    relationships: FxHashMap<ty::TyVid, ty::FoundRelationships>,
-
     // Is it OK to register obligations into this infcx inside
     // an infcx snapshot?
     //
@@ -85,19 +82,11 @@ static_assert_size!(PendingPredicateObligation<'_>, 72);
 impl<'a, 'tcx> FulfillmentContext<'tcx> {
     /// Creates a new fulfillment context.
     pub(super) fn new() -> FulfillmentContext<'tcx> {
-        FulfillmentContext {
-            predicates: ObligationForest::new(),
-            relationships: FxHashMap::default(),
-            usable_in_snapshot: false,
-        }
+        FulfillmentContext { predicates: ObligationForest::new(), usable_in_snapshot: false }
     }
 
     pub(super) fn new_in_snapshot() -> FulfillmentContext<'tcx> {
-        FulfillmentContext {
-            predicates: ObligationForest::new(),
-            relationships: FxHashMap::default(),
-            usable_in_snapshot: true,
-        }
+        FulfillmentContext { predicates: ObligationForest::new(), usable_in_snapshot: true }
     }
 
     /// Attempts to select obligations using `selcx`.
@@ -139,8 +128,6 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
 
         assert!(!infcx.is_in_snapshot() || self.usable_in_snapshot);
 
-        super::relationships::update(self, infcx, &obligation);
-
         self.predicates
             .register_obligation(PendingPredicateObligation { obligation, stalled_on: vec![] });
     }
@@ -164,10 +151,6 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
     fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
         self.predicates.map_pending_obligations(|o| o.obligation.clone())
     }
-
-    fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships> {
-        &mut self.relationships
-    }
 }
 
 struct FulfillProcessor<'a, 'tcx> {

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -14,7 +14,6 @@ mod object_safety;
 pub mod outlives_bounds;
 mod project;
 pub mod query;
-pub(crate) mod relationships;
 mod select;
 mod specialize;
 mod structural_match;

compiler/rustc_trait_selection/src/traits/relationships.rs

@@ -1,12 +1,5 @@
 // compile-flags: -Ztrait-solver=next
-// known-bug: unknown
-// failure-status: 101
-// dont-check-compiler-stderr
-
-// This test will fail until we fix `FulfillmentCtxt::relationships`. That's
-// because we create a type variable for closure upvar types, which is not
-// constrained until after we try to do fallback on diverging type variables.
-// Thus, we will call that function, which is unimplemented.
+// check-pass
 
 fn require_fn(_: impl Fn() -> i32) {}