Rollup merge of #155236 - adwinwhite:refactor-predicates-for-generics, r=lcnr

Normalize individual predicate of `InstantiatedPredicates` inside `predicates_for_generics`

This is a cleanup to better land rust-lang/rust#155083. It allows us to wrap individual clause in `Unnormalized` wrapper. See [this comment](https://github.com/rust-lang/rust/pull/155083#discussion_r3072219035)

Besides that, this PR also adds missing normalization in some cases.

r? @lcnr

compiler/rustc_hir_typeck/src/expr.rs

@@ -3557,6 +3557,8 @@ fn find_and_report_unsatisfied_index_impl(
             // Register the impl's predicates. One of these predicates
             // must be unsatisfied, or else we wouldn't have gotten here
             // in the first place.
+            let unnormalized_predicates =
+                self.tcx.predicates_of(impl_def_id).instantiate(self.tcx, impl_args);
             ocx.register_obligations(traits::predicates_for_generics(
                 |idx, span| {
                     cause.clone().derived_cause(
@@ -3574,8 +3576,9 @@ fn find_and_report_unsatisfied_index_impl(
                         },
                     )
                 },
+                |pred| ocx.normalize(&cause, self.param_env, pred),
                 self.param_env,
-                self.tcx.predicates_of(impl_def_id).instantiate(self.tcx, impl_args),
+                unnormalized_predicates,
             ));
 
             // Normalize the output type, which we can use later on as the

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -423,20 +423,6 @@ pub(crate) fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment
         }
     }
 
-    /// Instantiates and normalizes the bounds for a given item
-    pub(crate) fn instantiate_bounds(
-        &self,
-        span: Span,
-        def_id: DefId,
-        args: GenericArgsRef<'tcx>,
-    ) -> ty::InstantiatedPredicates<'tcx> {
-        let bounds = self.tcx.predicates_of(def_id);
-        let result = bounds.instantiate(self.tcx, args);
-        let result = self.normalize(span, result);
-        debug!("instantiate_bounds(bounds={:?}, args={:?}) = {:?}", bounds, args, result);
-        result
-    }
-
     pub(crate) fn normalize<T>(&self, span: Span, value: T) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
@@ -1426,10 +1412,11 @@ pub(crate) fn add_required_obligations_with_code(
     ) {
         let param_env = self.param_env;
 
-        let bounds = self.instantiate_bounds(span, def_id, args);
+        let bounds = self.tcx.predicates_of(def_id).instantiate(self.tcx, args);
 
         for obligation in traits::predicates_for_generics(
             |idx, predicate_span| self.cause(span, code(idx, predicate_span)),
+            |pred| self.normalize(span, pred),
             param_env,
             bounds,
         ) {

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -339,9 +339,9 @@ fn select_inherent_assoc_candidates(
 
             // Check whether the impl imposes obligations we have to worry about.
             let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args);
-            let impl_bounds = ocx.normalize(&ObligationCause::dummy(), self.param_env, impl_bounds);
             let impl_obligations = traits::predicates_for_generics(
                 |_, _| ObligationCause::dummy(),
+                |pred| ocx.normalize(&ObligationCause::dummy(), self.param_env, pred),
                 self.param_env,
                 impl_bounds,
             );

compiler/rustc_hir_typeck/src/method/confirm.rs

@@ -144,8 +144,7 @@ fn confirm(
         );
         self.unify_receivers(self_ty, method_sig_rcvr, pick);
 
-        let (method_sig, method_predicates) =
-            self.normalize(self.span, (method_sig, method_predicates));
+        let method_sig = self.normalize(self.span, method_sig);
 
         // Make sure nobody calls `drop()` explicitly.
         self.check_for_illegal_method_calls(pick);
@@ -626,6 +625,7 @@ fn add_obligations(
                 );
                 self.cause(self.span, code)
             },
+            |pred| self.normalize(self.call_expr.span, pred),
             self.param_env,
             method_predicates,
         ) {

compiler/rustc_hir_typeck/src/method/mod.rs

@@ -442,17 +442,21 @@ pub(super) fn lookup_method_for_operator(
         // any late-bound regions appearing in its bounds.
         let bounds = self.tcx.predicates_of(def_id).instantiate(self.tcx, args);
 
-        let InferOk { value: bounds, obligations: o } =
-            self.at(&obligation.cause, self.param_env).normalize(bounds);
-        obligations.extend(o);
-        assert!(!bounds.has_escaping_bound_vars());
-
         let predicates_cause = obligation.cause.clone();
+        let mut normalization_obligations = PredicateObligations::new();
         obligations.extend(traits::predicates_for_generics(
             move |_, _| predicates_cause.clone(),
+            |pred| {
+                let InferOk { value: pred, obligations: o } =
+                    self.at(&obligation.cause, self.param_env).normalize(pred);
+                normalization_obligations.extend(o);
+                assert!(!pred.has_escaping_bound_vars());
+                pred
+            },
             self.param_env,
             bounds,
         ));
+        obligations.extend(normalization_obligations);
 
         // Also add an obligation for the method type being well-formed.
         debug!(

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1989,7 +1989,6 @@ fn consider_probe(
                     let impl_def_id = probe.item.container_id(self.tcx);
                     let impl_bounds =
                         self.tcx.predicates_of(impl_def_id).instantiate(self.tcx, impl_args);
-                    let impl_bounds = ocx.normalize(cause, self.param_env, impl_bounds);
                     // Convert the bounds into obligations.
                     ocx.register_obligations(traits::predicates_for_generics(
                         |idx, span| {
@@ -2001,6 +2000,7 @@ fn consider_probe(
                             );
                             self.cause(self.span, code)
                         },
+                        |pred| ocx.normalize(cause, self.param_env, pred),
                         self.param_env,
                         impl_bounds,
                     ));

compiler/rustc_middle/src/ty/mod.rs

@@ -689,7 +689,7 @@ fn pack(self) -> Term<'tcx> {
 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
 /// [usize:Bar<isize>]]`.
-#[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
+#[derive(Clone, Debug)]
 pub struct InstantiatedPredicates<'tcx> {
     pub predicates: Vec<Clause<'tcx>>,
     pub spans: Vec<Span>,

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -34,8 +34,8 @@
 use rustc_middle::span_bug;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::{
-    self, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
-    TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypingMode, Upcast,
+    self, Clause, GenericArgs, GenericArgsRef, Ty, TyCtxt, TypeFoldable, TypeFolder,
+    TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypingMode, Upcast,
 };
 use rustc_span::Span;
 use rustc_span::def_id::DefId;
@@ -177,9 +177,10 @@ pub enum TraitQueryMode {
 }
 
 /// Creates predicate obligations from the generic bounds.
-#[instrument(level = "debug", skip(cause, param_env))]
+#[instrument(level = "debug", skip(cause, param_env, normalize_predicate))]
 pub fn predicates_for_generics<'tcx>(
     cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
+    mut normalize_predicate: impl FnMut(Clause<'tcx>) -> Clause<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     generic_bounds: ty::InstantiatedPredicates<'tcx>,
 ) -> impl Iterator<Item = PredicateObligation<'tcx>> {
@@ -187,7 +188,7 @@ pub fn predicates_for_generics<'tcx>(
         cause: cause(idx, span),
         recursion_depth: 0,
         param_env,
-        predicate: clause.as_predicate(),
+        predicate: normalize_predicate(clause).as_predicate(),
     })
 }
 

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

@@ -185,12 +185,13 @@ fn fulfill_implication<'tcx>(
     // Now check that the source trait ref satisfies all the where clauses of the target impl.
     // This is not just for correctness; we also need this to constrain any params that may
     // only be referenced via projection predicates.
-    let predicates = ocx.normalize(
-        cause,
+    let predicates = infcx.tcx.predicates_of(target_impl).instantiate(infcx.tcx, target_args);
+    let obligations = predicates_for_generics(
+        |_, _| cause.clone(),
+        |pred| ocx.normalize(cause, param_env, pred),
         param_env,
-        infcx.tcx.predicates_of(target_impl).instantiate(infcx.tcx, target_args),
+        predicates,
     );
-    let obligations = predicates_for_generics(|_, _| cause.clone(), param_env, predicates);
     ocx.register_obligations(obligations);
 
     let errors = ocx.evaluate_obligations_error_on_ambiguity();
@@ -315,12 +316,14 @@ pub(super) fn specializes(
     // Now check that the source trait ref satisfies all the where clauses of the target impl.
     // This is not just for correctness; we also need this to constrain any params that may
     // only be referenced via projection predicates.
-    let predicates = ocx.normalize(
-        cause,
+    let predicates =
+        infcx.tcx.predicates_of(parent_impl_def_id).instantiate(infcx.tcx, parent_args);
+    let obligations = predicates_for_generics(
+        |_, _| cause.clone(),
+        |pred| ocx.normalize(cause, param_env, pred),
         param_env,
-        infcx.tcx.predicates_of(parent_impl_def_id).instantiate(infcx.tcx, parent_args),
+        predicates,
     );
-    let obligations = predicates_for_generics(|_, _| cause.clone(), param_env, predicates);
     ocx.register_obligations(obligations);
 
     let errors = ocx.evaluate_obligations_error_on_ambiguity();

tests/ui/associated-types/hr-associated-type-bound-param-6.stderr

@@ -9,18 +9,6 @@ help: consider restricting type parameter `T` with trait `X`
 LL | impl<S, T: for<'b> X<'b, T>> X<'_, T> for (S,) {
    |          ++++++++++++++++++
 
-error[E0277]: the trait bound `for<'b> i32: X<'b, i32>` is not satisfied
-  --> $DIR/hr-associated-type-bound-param-6.rs:18:5
-   |
-LL |     <(i32,) as X<i32>>::f("abc");
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'b> X<'b, i32>` is not implemented for `i32`
-   |
-help: the trait `X<'_, T>` is implemented for `(S,)`
-  --> $DIR/hr-associated-type-bound-param-6.rs:12:1
-   |
-LL | impl<S, T> X<'_, T> for (S,) {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error[E0277]: the trait bound `for<'b> i32: X<'b, i32>` is not satisfied
   --> $DIR/hr-associated-type-bound-param-6.rs:18:18
    |
@@ -41,6 +29,18 @@ LL |     for<'b> T: X<'b, T>,
 LL |     fn f(x: &<T as X<'_, T>>::U) {
    |        - required by a bound in this associated function
 
+error[E0277]: the trait bound `for<'b> i32: X<'b, i32>` is not satisfied
+  --> $DIR/hr-associated-type-bound-param-6.rs:18:5
+   |
+LL |     <(i32,) as X<i32>>::f("abc");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'b> X<'b, i32>` is not implemented for `i32`
+   |
+help: the trait `X<'_, T>` is implemented for `(S,)`
+  --> $DIR/hr-associated-type-bound-param-6.rs:12:1
+   |
+LL | impl<S, T> X<'_, T> for (S,) {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0277]: the trait bound `i32: X<'_, i32>` is not satisfied
   --> $DIR/hr-associated-type-bound-param-6.rs:18:27
    |