change writeback: ICEs as the regions have already been resolved

Author: lcnr

compiler/rustc_hir_typeck/src/writeback.rs

@@ -8,12 +8,15 @@ use rustc_errors::{ErrorGuaranteed, StashKey};
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
+use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
+use rustc_trait_selection::solve;
+use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
 
 use std::mem;
 
@@ -778,14 +781,21 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Resolver<'cx, 'tcx> {
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
         let tcx = self.fcx.tcx;
         match self.fcx.fully_resolve(t) {
-            Ok(t) if self.fcx.next_trait_solver() => {
-                // We must normalize erasing regions here, since later lints
+            Ok(ty) if self.fcx.next_trait_solver() => {
+                // We must deeply normalize here, since later lints
                 // expect that types that show up in the typeck are fully
                 // normalized.
-                if let Ok(t) = tcx.try_normalize_erasing_regions(self.fcx.param_env, t) {
-                    t
-                } else {
-                    tcx.fold_regions(t, |_, _| tcx.lifetimes.re_erased)
+
+                // FIXME(-Ztrait-solver=next): This is probably not
+                // very performant.
+                let body_id = tcx.hir().body_owner_def_id(self.body.id());
+                let cause = ObligationCause::misc(self.span.to_span(tcx), body_id);
+                match solve::deeply_normalize(self.fcx.at(&cause, self.fcx.param_env), ty) {
+                    Ok(ty) => tcx.fold_regions(ty, |_, _| tcx.lifetimes.re_erased),
+                    Err(errors) => {
+                        let guar = self.fcx.err_ctxt().report_fulfillment_errors(errors);
+                        Ty::new_error(tcx, guar)
+                    }
                 }
             }
             Ok(t) => {

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -42,8 +42,9 @@ mod trait_goals;
 
 pub use eval_ctxt::{EvalCtxt, GenerateProofTree, InferCtxtEvalExt, InferCtxtSelectExt};
 pub use fulfill::FulfillmentCtxt;
+pub use normalize::deeply_normalize;
 pub(crate) use normalize::{
-    deeply_normalize, deeply_normalize_for_diagnostics, deeply_normalize_with_skipped_universes,
+    deeply_normalize_for_diagnostics, deeply_normalize_with_skipped_universes,
 };
 
 #[derive(Debug, Clone, Copy)]

compiler/rustc_trait_selection/src/solve/normalize.rs

@@ -17,7 +17,7 @@ use super::FulfillmentCtxt;
 
 /// Deeply normalize all aliases in `value`. This does not handle inference and expects
 /// its input to be already fully resolved.
-pub(crate) fn deeply_normalize<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
+pub fn deeply_normalize<'tcx, T: TypeFoldable<TyCtxt<'tcx>>>(
     at: At<'_, 'tcx>,
     value: T,
 ) -> Result<T, Vec<FulfillmentError<'tcx>>> {