Change InferCtxtBuilder from enter to build

compiler/rustc_trait_selection/src/traits/codegen.rs

@@ -29,60 +29,61 @@ pub fn codegen_select_candidate<'tcx>(
 
     // Do the initial selection for the obligation. This yields the
     // shallow result we are looking for -- that is, what specific impl.
-    let mut infcx_builder =
-        tcx.infer_ctxt().ignoring_regions().with_opaque_type_inference(DefiningAnchor::Bubble);
-    infcx_builder.enter(|infcx| {
-        //~^ HACK `Bubble` is required for
-        // this test to pass: type-alias-impl-trait/assoc-projection-ice.rs
-        let mut selcx = SelectionContext::new(&infcx);
+    let infcx = tcx
+        .infer_ctxt()
+        .ignoring_regions()
+        .with_opaque_type_inference(DefiningAnchor::Bubble)
+        .build();
+    //~^ HACK `Bubble` is required for
+    // this test to pass: type-alias-impl-trait/assoc-projection-ice.rs
+    let mut selcx = SelectionContext::new(&infcx);
 
-        let obligation_cause = ObligationCause::dummy();
-        let obligation =
-            Obligation::new(obligation_cause, param_env, trait_ref.to_poly_trait_predicate());
+    let obligation_cause = ObligationCause::dummy();
+    let obligation =
+        Obligation::new(obligation_cause, param_env, trait_ref.to_poly_trait_predicate());
 
-        let selection = match selcx.select(&obligation) {
-            Ok(Some(selection)) => selection,
-            Ok(None) => return Err(CodegenObligationError::Ambiguity),
-            Err(Unimplemented) => return Err(CodegenObligationError::Unimplemented),
-            Err(e) => {
-                bug!("Encountered error `{:?}` selecting `{:?}` during codegen", e, trait_ref)
-            }
-        };
-
-        debug!(?selection);
-
-        // Currently, we use a fulfillment context to completely resolve
-        // all nested obligations. This is because they can inform the
-        // inference of the impl's type parameters.
-        let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(tcx);
-        let impl_source = selection.map(|predicate| {
-            fulfill_cx.register_predicate_obligation(&infcx, predicate);
-        });
-
-        // In principle, we only need to do this so long as `impl_source`
-        // contains unbound type parameters. It could be a slight
-        // optimization to stop iterating early.
-        let errors = fulfill_cx.select_all_or_error(&infcx);
-        if !errors.is_empty() {
-            // `rustc_monomorphize::collector` assumes there are no type errors.
-            // Cycle errors are the only post-monomorphization errors possible; emit them now so
-            // `rustc_ty_utils::resolve_associated_item` doesn't return `None` post-monomorphization.
-            for err in errors {
-                if let FulfillmentErrorCode::CodeCycle(cycle) = err.code {
-                    infcx.err_ctxt().report_overflow_error_cycle(&cycle);
-                }
-            }
-            return Err(CodegenObligationError::FulfillmentError);
+    let selection = match selcx.select(&obligation) {
+        Ok(Some(selection)) => selection,
+        Ok(None) => return Err(CodegenObligationError::Ambiguity),
+        Err(Unimplemented) => return Err(CodegenObligationError::Unimplemented),
+        Err(e) => {
+            bug!("Encountered error `{:?}` selecting `{:?}` during codegen", e, trait_ref)
         }
+    };
 
-        let impl_source = infcx.resolve_vars_if_possible(impl_source);
-        let impl_source = infcx.tcx.erase_regions(impl_source);
+    debug!(?selection);
 
-        // Opaque types may have gotten their hidden types constrained, but we can ignore them safely
-        // as they will get constrained elsewhere, too.
-        // (ouz-a) This is required for `type-alias-impl-trait/assoc-projection-ice.rs` to pass
-        let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
+    // Currently, we use a fulfillment context to completely resolve
+    // all nested obligations. This is because they can inform the
+    // inference of the impl's type parameters.
+    let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(tcx);
+    let impl_source = selection.map(|predicate| {
+        fulfill_cx.register_predicate_obligation(&infcx, predicate);
+    });
 
-        Ok(&*tcx.arena.alloc(impl_source))
-    })
+    // In principle, we only need to do this so long as `impl_source`
+    // contains unbound type parameters. It could be a slight
+    // optimization to stop iterating early.
+    let errors = fulfill_cx.select_all_or_error(&infcx);
+    if !errors.is_empty() {
+        // `rustc_monomorphize::collector` assumes there are no type errors.
+        // Cycle errors are the only post-monomorphization errors possible; emit them now so
+        // `rustc_ty_utils::resolve_associated_item` doesn't return `None` post-monomorphization.
+        for err in errors {
+            if let FulfillmentErrorCode::CodeCycle(cycle) = err.code {
+                infcx.err_ctxt().report_overflow_error_cycle(&cycle);
+            }
+        }
+        return Err(CodegenObligationError::FulfillmentError);
+    }
+
+    let impl_source = infcx.resolve_vars_if_possible(impl_source);
+    let impl_source = infcx.tcx.erase_regions(impl_source);
+
+    // Opaque types may have gotten their hidden types constrained, but we can ignore them safely
+    // as they will get constrained elsewhere, too.
+    // (ouz-a) This is required for `type-alias-impl-trait/assoc-projection-ice.rs` to pass
+    let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
+
+    Ok(&*tcx.arena.alloc(impl_source))
 }