use TypingEnv when no infcx is available

the behavior of the type system not only depends on the current
assumptions, but also the currentnphase of the compiler. This is
mostly necessary as we need to decide whether and how to reveal
opaque types. We track this via the `TypingMode`.

compiler/rustc_traits/src/codegen.rs

@@ -6,7 +6,7 @@
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::bug;
 use rustc_middle::traits::CodegenObligationError;
-use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt, TypingMode};
+use rustc_middle::ty::{self, PseudoCanonicalInput, TyCtxt, TypeVisitableExt};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::traits::{
     ImplSource, Obligation, ObligationCause, ObligationCtxt, ScrubbedTraitError, SelectionContext,
@@ -23,14 +23,15 @@ use tracing::debug;
 /// This also expects that `trait_ref` is fully normalized.
 pub(crate) fn codegen_select_candidate<'tcx>(
     tcx: TyCtxt<'tcx>,
-    (param_env, trait_ref): (ty::ParamEnv<'tcx>, ty::TraitRef<'tcx>),
+    key: PseudoCanonicalInput<'tcx, ty::TraitRef<'tcx>>,
 ) -> Result<&'tcx ImplSource<'tcx, ()>, CodegenObligationError> {
+    let PseudoCanonicalInput { typing_env, value: trait_ref } = key;
     // We expect the input to be fully normalized.
-    debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(param_env, trait_ref));
+    debug_assert_eq!(trait_ref, tcx.normalize_erasing_regions(typing_env, trait_ref));
 
     // Do the initial selection for the obligation. This yields the
     // shallow result we are looking for -- that is, what specific impl.
-    let infcx = tcx.infer_ctxt().ignoring_regions().build(TypingMode::from_param_env(param_env));
+    let (infcx, param_env) = tcx.infer_ctxt().ignoring_regions().build_with_typing_env(typing_env);
     let mut selcx = SelectionContext::new(&infcx);
 
     let obligation_cause = ObligationCause::dummy();