Get rid of infer vars in inherent assoc types selection by using Eage…

…rResolver folder

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -32,13 +32,14 @@ use rustc_middle::middle::stability::AllowUnstable;
 use rustc_middle::ty::GenericParamDefKind;
 use rustc_middle::ty::{
     self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, ParamEnv, Predicate, Ty, TyCtxt,
-    TypeVisitableExt,
+    TypeFoldable, TypeVisitableExt,
 };
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::{sym, BytePos, Span, DUMMY_SP};
 use rustc_target::spec::abi;
+use rustc_trait_selection::solve::eval_ctxt::canonical::EagerResolver;
 use rustc_trait_selection::traits::wf::object_region_bounds;
 use rustc_trait_selection::traits::{self, NormalizeExt, ObligationCtxt};
 
@@ -1648,6 +1649,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 );
 
                 let ty = Ty::new_alias(tcx, ty::Inherent, ty::AliasTy::new(tcx, assoc_item, args));
+                let ty = ty.fold_with(&mut EagerResolver { infcx });
 
                 Ok(Some((ty, assoc_item)))
             },

compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs

@@ -365,8 +365,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 }
 
 /// Resolves ty, region, and const vars to their inferred values or their root vars.
-struct EagerResolver<'a, 'tcx> {
-    infcx: &'a InferCtxt<'tcx>,
+pub struct EagerResolver<'a, 'tcx> {
+    pub infcx: &'a InferCtxt<'tcx>,
 }
 
 impl<'tcx> TypeFolder<TyCtxt<'tcx>> for EagerResolver<'_, 'tcx> {

compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs

@@ -33,7 +33,7 @@ use super::{search_graph, GoalEvaluationKind};
 use super::{search_graph::SearchGraph, Goal};
 pub use select::InferCtxtSelectExt;
 
-mod canonical;
+pub mod canonical;
 mod commit_if_ok;
 mod probe;
 mod select;

compiler/rustc_trait_selection/src/solve/mod.rs

@@ -31,7 +31,7 @@ use rustc_middle::ty::{
 mod alias_relate;
 mod assembly;
 mod canonicalize;
-mod eval_ctxt;
+pub mod eval_ctxt;
 mod fulfill;
 pub mod inspect;
 mod normalize;