Auto merge of #99015 - lcnr:fn-ctxt-no-more, r=compiler-errors

stop using `FnCtxt` outside of hir typeck

the requirements between **hir typeck**™, and **not hir typeck**™ are different enough to warrant a full split. with this PR `FnCtxt` is now only used for hir typeck (and for one clippy lint which seems to be emulating hir typeck).

Once this PR has landed I intend to move `FnCtxt` into a new crate. This should also allow some further general improvements here.

r? rust-lang/types

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -181,11 +181,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                         let generic_ty = type_test.generic_kind.to_ty(self.infcx.tcx);
                         let origin = RelateParamBound(type_test_span, generic_ty, None);
                         self.buffer_error(self.infcx.construct_generic_bound_failure(
+                            self.body.source.def_id().expect_local(),
                             type_test_span,
                             Some(origin),
                             type_test.generic_kind,
                             lower_bound_region,
-                            self.body.source.def_id().as_local(),
                         ));
                     } else {
                         // FIXME. We should handle this case better. It

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -63,7 +63,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString, Mul
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::lang_items::LangItem;
-use rustc_hir::{Item, ItemKind, Node};
+use rustc_hir::Node;
 use rustc_middle::dep_graph::DepContext;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{
@@ -348,7 +348,11 @@ pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
 }
 
 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
-    pub fn report_region_errors(&self, errors: &[RegionResolutionError<'tcx>]) {
+    pub fn report_region_errors(
+        &self,
+        generic_param_scope: LocalDefId,
+        errors: &[RegionResolutionError<'tcx>],
+    ) {
         debug!("report_region_errors(): {} errors to start", errors.len());
 
         // try to pre-process the errors, which will group some of them
@@ -379,6 +383,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
                     RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
                         self.report_generic_bound_failure(
+                            generic_param_scope,
                             origin.span(),
                             Some(origin),
                             param_ty,
@@ -2269,56 +2274,30 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
     pub fn report_generic_bound_failure(
         &self,
+        generic_param_scope: LocalDefId,
         span: Span,
         origin: Option<SubregionOrigin<'tcx>>,
         bound_kind: GenericKind<'tcx>,
         sub: Region<'tcx>,
     ) {
-        let owner =
-            self.in_progress_typeck_results.map(|typeck_results| typeck_results.borrow().hir_owner);
-        self.construct_generic_bound_failure(span, origin, bound_kind, sub, owner).emit();
+        self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
+            .emit();
     }
 
     pub fn construct_generic_bound_failure(
         &self,
+        generic_param_scope: LocalDefId,
         span: Span,
         origin: Option<SubregionOrigin<'tcx>>,
         bound_kind: GenericKind<'tcx>,
         sub: Region<'tcx>,
-        owner: Option<LocalDefId>,
     ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
-        let hir = self.tcx.hir();
         // Attempt to obtain the span of the parameter so we can
         // suggest adding an explicit lifetime bound to it.
-        let generics = owner.map(|owner| {
-            let hir_id = hir.local_def_id_to_hir_id(owner);
-            let parent_id = hir.get_parent_item(hir_id);
-            (
-                // Parent item could be a `mod`, so we check the HIR before calling:
-                if let Some(Node::Item(Item {
-                    kind: ItemKind::Trait(..) | ItemKind::Impl { .. },
-                    ..
-                })) = hir.find_by_def_id(parent_id)
-                {
-                    Some(self.tcx.generics_of(parent_id))
-                } else {
-                    None
-                },
-                self.tcx.generics_of(owner.to_def_id()),
-                hir.span(hir_id),
-            )
-        });
-
-        let span = match generics {
-            // This is to get around the trait identity obligation, that has a `DUMMY_SP` as signal
-            // for other diagnostics, so we need to recover it here.
-            Some((_, _, node)) if span.is_dummy() => node,
-            _ => span,
-        };
-
+        let generics = self.tcx.generics_of(generic_param_scope);
         // type_param_span is (span, has_bounds)
-        let type_param_span = match (generics, bound_kind) {
-            (Some((_, ref generics, _)), GenericKind::Param(ref param)) => {
+        let type_param_span = match bound_kind {
+            GenericKind::Param(ref param) => {
                 // Account for the case where `param` corresponds to `Self`,
                 // which doesn't have the expected type argument.
                 if !(generics.has_self && param.index == 0) {
@@ -2346,30 +2325,23 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             }
             _ => None,
         };
-        let new_lt = generics
-            .as_ref()
-            .and_then(|(parent_g, g, _)| {
-                let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
-                let mut lts_names = g
-                    .params
-                    .iter()
+
+        let new_lt = {
+            let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
+            let lts_names =
+                iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
+                    .flat_map(|g| &g.params)
                     .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
                     .map(|p| p.name.as_str())
                     .collect::<Vec<_>>();
-                if let Some(g) = parent_g {
-                    lts_names.extend(
-                        g.params
-                            .iter()
-                            .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
-                            .map(|p| p.name.as_str()),
-                    );
-                }
-                possible.find(|candidate| !lts_names.contains(&&candidate[..]))
-            })
-            .unwrap_or("'lt".to_string());
+            possible
+                .find(|candidate| !lts_names.contains(&&candidate[..]))
+                .unwrap_or("'lt".to_string())
+        };
+
         let add_lt_sugg = generics
-            .as_ref()
-            .and_then(|(_, g, _)| g.params.first())
+            .params
+            .first()
             .and_then(|param| param.def_id.as_local())
             .map(|def_id| (self.tcx.def_span(def_id).shrink_to_lo(), format!("{}, ", new_lt)));
 
@@ -2571,7 +2543,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 );
                 if let Some(infer::RelateParamBound(_, t, _)) = origin {
                     let return_impl_trait =
-                        owner.and_then(|owner| self.tcx.return_type_impl_trait(owner)).is_some();
+                        self.tcx.return_type_impl_trait(generic_param_scope).is_some();
                     let t = self.resolve_vars_if_possible(t);
                     match t.kind() {
                         // We've got:

compiler/rustc_infer/src/infer/mod.rs

@@ -1301,7 +1301,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     /// result. After this, no more unification operations should be
     /// done -- or the compiler will panic -- but it is legal to use
     /// `resolve_vars_if_possible` as well as `fully_resolve`.
-    pub fn resolve_regions_and_report_errors(&self, outlives_env: &OutlivesEnvironment<'tcx>) {
+    pub fn resolve_regions_and_report_errors(
+        &self,
+        generic_param_scope: LocalDefId,
+        outlives_env: &OutlivesEnvironment<'tcx>,
+    ) {
         let errors = self.resolve_regions(outlives_env);
 
         if !self.is_tainted_by_errors() {
@@ -1310,7 +1314,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             // this infcx was in use.  This is totally hokey but
             // otherwise we have a hard time separating legit region
             // errors from silly ones.
-            self.report_region_errors(&errors);
+            self.report_region_errors(generic_param_scope, &errors);
         }
     }
 

compiler/rustc_infer/src/infer/outlives/obligations.rs

@@ -68,6 +68,7 @@ use crate::infer::{
 };
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::undo_log::UndoLogs;
+use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, Region, Ty, TyCtxt, TypeVisitable};
 use smallvec::smallvec;
@@ -163,14 +164,15 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
 
     pub fn check_region_obligations_and_report_errors(
         &self,
+        generic_param_scope: LocalDefId,
         outlives_env: &OutlivesEnvironment<'tcx>,
     ) {
         self.process_registered_region_obligations(
             outlives_env.region_bound_pairs(),
             outlives_env.param_env,
         );
 
-        self.resolve_regions_and_report_errors(outlives_env)
+        self.resolve_regions_and_report_errors(generic_param_scope, outlives_env)
     }
 }
 

compiler/rustc_trait_selection/src/traits/engine.rs

@@ -1,10 +1,22 @@
-use rustc_middle::ty::TyCtxt;
+use std::cell::RefCell;
 
 use super::TraitEngine;
 use super::{ChalkFulfillmentContext, FulfillmentContext};
+use crate::infer::InferCtxtExt;
+use rustc_hir::def_id::DefId;
+use rustc_infer::infer::{InferCtxt, InferOk};
+use rustc_infer::traits::{
+    FulfillmentError, Obligation, ObligationCause, PredicateObligation, TraitEngineExt as _,
+};
+use rustc_middle::ty::error::TypeError;
+use rustc_middle::ty::ToPredicate;
+use rustc_middle::ty::TypeFoldable;
+use rustc_middle::ty::{self, Ty, TyCtxt};
 
 pub trait TraitEngineExt<'tcx> {
     fn new(tcx: TyCtxt<'tcx>) -> Box<Self>;
+
+    fn new_ignoring_regions(tcx: TyCtxt<'tcx>) -> Box<Self>;
 }
 
 impl<'tcx> TraitEngineExt<'tcx> for dyn TraitEngine<'tcx> {
@@ -15,4 +27,96 @@ impl<'tcx> TraitEngineExt<'tcx> for dyn TraitEngine<'tcx> {
             Box::new(FulfillmentContext::new())
         }
     }
+
+    fn new_ignoring_regions(tcx: TyCtxt<'tcx>) -> Box<Self> {
+        if tcx.sess.opts.unstable_opts.chalk {
+            Box::new(ChalkFulfillmentContext::new())
+        } else {
+            Box::new(FulfillmentContext::new_ignoring_regions())
+        }
+    }
+}
+
+/// Used if you want to have pleasant experience when dealing
+/// with obligations outside of hir or mir typeck.
+pub struct ObligationCtxt<'a, 'tcx> {
+    pub infcx: &'a InferCtxt<'a, 'tcx>,
+    engine: RefCell<Box<dyn TraitEngine<'tcx>>>,
+}
+
+impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
+    pub fn new(infcx: &'a InferCtxt<'a, 'tcx>) -> Self {
+        Self { infcx, engine: RefCell::new(<dyn TraitEngine<'_>>::new(infcx.tcx)) }
+    }
+
+    pub fn register_obligation(&self, obligation: PredicateObligation<'tcx>) {
+        self.engine.borrow_mut().register_predicate_obligation(self.infcx, obligation);
+    }
+
+    pub fn register_obligations(
+        &self,
+        obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>,
+    ) {
+        // Can't use `register_predicate_obligations` because the iterator
+        // may also use this `ObligationCtxt`.
+        for obligation in obligations {
+            self.engine.borrow_mut().register_predicate_obligation(self.infcx, obligation)
+        }
+    }
+
+    pub fn register_infer_ok_obligations<T>(&self, infer_ok: InferOk<'tcx, T>) -> T {
+        let InferOk { value, obligations } = infer_ok;
+        self.engine.borrow_mut().register_predicate_obligations(self.infcx, obligations);
+        value
+    }
+
+    /// Requires that `ty` must implement the trait with `def_id` in
+    /// the given environment. This trait must not have any type
+    /// parameters (except for `Self`).
+    pub fn register_bound(
+        &self,
+        cause: ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: Ty<'tcx>,
+        def_id: DefId,
+    ) {
+        let tcx = self.infcx.tcx;
+        let trait_ref = ty::TraitRef { def_id, substs: tcx.mk_substs_trait(ty, &[]) };
+        self.register_obligation(Obligation {
+            cause,
+            recursion_depth: 0,
+            param_env,
+            predicate: ty::Binder::dummy(trait_ref).without_const().to_predicate(tcx),
+        });
+    }
+
+    pub fn normalize<T: TypeFoldable<'tcx>>(
+        &self,
+        cause: ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        value: T,
+    ) -> T {
+        let infer_ok = self.infcx.partially_normalize_associated_types_in(cause, param_env, value);
+        self.register_infer_ok_obligations(infer_ok)
+    }
+
+    pub fn equate_types(
+        &self,
+        cause: &ObligationCause<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        expected: Ty<'tcx>,
+        actual: Ty<'tcx>,
+    ) -> Result<(), TypeError<'tcx>> {
+        match self.infcx.at(cause, param_env).eq(expected, actual) {
+            Ok(InferOk { obligations, value: () }) => {
+                self.register_obligations(obligations);
+                Ok(())
+            }
+            Err(e) => Err(e),
+        }
+    }
+
+    pub fn select_all_or_error(&self) -> Vec<FulfillmentError<'tcx>> {
+        self.engine.borrow_mut().select_all_or_error(self.infcx)
+    }
 }

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -47,7 +47,7 @@ pub use self::SelectionError::*;
 
 pub use self::coherence::{add_placeholder_note, orphan_check, overlapping_impls};
 pub use self::coherence::{OrphanCheckErr, OverlapResult};
-pub use self::engine::TraitEngineExt;
+pub use self::engine::{ObligationCtxt, TraitEngineExt};
 pub use self::fulfill::{FulfillmentContext, PendingPredicateObligation};
 pub use self::object_safety::astconv_object_safety_violations;
 pub use self::object_safety::is_vtable_safe_method;
@@ -237,29 +237,37 @@ fn do_normalize_predicates<'tcx>(
         // cares about declarations like `'a: 'b`.
         let outlives_env = OutlivesEnvironment::new(elaborated_env);
 
-        infcx.resolve_regions_and_report_errors(&outlives_env);
+        // FIXME: It's very weird that we ignore region obligations but apparently
+        // still need to use `resolve_regions` as we need the resolved regions in
+        // the normalized predicates.
+        let errors = infcx.resolve_regions(&outlives_env);
+        if !errors.is_empty() {
+            tcx.sess.delay_span_bug(
+                span,
+                format!(
+                    "failed region resolution while normalizing {elaborated_env:?}: {errors:?}"
+                ),
+            );
+        }
 
-        let predicates = match infcx.fully_resolve(predicates) {
-            Ok(predicates) => predicates,
+        match infcx.fully_resolve(predicates) {
+            Ok(predicates) => Ok(predicates),
             Err(fixup_err) => {
                 // If we encounter a fixup error, it means that some type
                 // variable wound up unconstrained. I actually don't know
                 // if this can happen, and I certainly don't expect it to
                 // happen often, but if it did happen it probably
                 // represents a legitimate failure due to some kind of
-                // unconstrained variable, and it seems better not to ICE,
-                // all things considered.
-                let reported = tcx.sess.span_err(span, &fixup_err.to_string());
-                return Err(reported);
+                // unconstrained variable.
+                //
+                // @lcnr: Let's still ICE here for now. I want a test case
+                // for that.
+                span_bug!(
+                    span,
+                    "inference variables in normalized parameter environment: {}",
+                    fixup_err
+                );
             }
-        };
-        if predicates.needs_infer() {
-            let reported = tcx
-                .sess
-                .delay_span_bug(span, "encountered inference variables after `fully_resolve`");
-            Err(reported)
-        } else {
-            Ok(predicates)
         }
     })
 }