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`.

1 files changed, 17 insertions, 10 deletions

diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 260c6543f98..425cb059e57 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -39,7 +39,7 @@ use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::ty::print::{FmtPrinter, Printer, pretty_print_const, with_no_trimmed_paths};
 use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{
-    self, AdtDef, GenericArg, GenericArgsRef, Instance, InstanceKind, List, Ty, TyCtxt, TypingMode,
+    self, AdtDef, GenericArg, GenericArgsRef, Instance, InstanceKind, List, Ty, TyCtxt, TypingEnv,
     UserTypeAnnotationIndex,
 };
 
@@ -452,12 +452,17 @@ impl<'tcx> Body<'tcx> {
         self.basic_blocks.as_mut()
     }
 
-    pub fn typing_mode(&self, _tcx: TyCtxt<'tcx>) -> TypingMode<'tcx> {
+    pub fn typing_env(&self, tcx: TyCtxt<'tcx>) -> TypingEnv<'tcx> {
         match self.phase {
-            // FIXME(#132279): the MIR is quite clearly inside of a body, so we
-            // should instead reveal opaques defined by that body here.
-            MirPhase::Built | MirPhase::Analysis(_) => TypingMode::non_body_analysis(),
-            MirPhase::Runtime(_) => TypingMode::PostAnalysis,
+            // FIXME(#132279): we should reveal the opaques defined in the body during analysis.
+            MirPhase::Built | MirPhase::Analysis(_) => TypingEnv {
+                typing_mode: ty::TypingMode::non_body_analysis(),
+                param_env: tcx.param_env(self.source.def_id()),
+            },
+            MirPhase::Runtime(_) => TypingEnv {
+                typing_mode: ty::TypingMode::PostAnalysis,
+                param_env: tcx.param_env_reveal_all_normalized(self.source.def_id()),
+            },
         }
     }
 
@@ -618,7 +623,7 @@ impl<'tcx> Body<'tcx> {
     }
 
     /// If this basic block ends with a [`TerminatorKind::SwitchInt`] for which we can evaluate the
-    /// dimscriminant in monomorphization, we return the discriminant bits and the
+    /// discriminant in monomorphization, we return the discriminant bits and the
     /// [`SwitchTargets`], just so the caller doesn't also have to match on the terminator.
     fn try_const_mono_switchint<'a>(
         tcx: TyCtxt<'tcx>,
@@ -627,13 +632,15 @@ impl<'tcx> Body<'tcx> {
     ) -> Option<(u128, &'a SwitchTargets)> {
         // There are two places here we need to evaluate a constant.
         let eval_mono_const = |constant: &ConstOperand<'tcx>| {
-            let env = ty::ParamEnv::reveal_all();
+            // FIXME(#132279): what is this, why are we using an empty environment with
+            // `RevealAll` here.
+            let typing_env = ty::TypingEnv::fully_monomorphized();
             let mono_literal = instance.instantiate_mir_and_normalize_erasing_regions(
                 tcx,
-                env,
+                typing_env,
                 crate::ty::EarlyBinder::bind(constant.const_),
             );
-            mono_literal.try_eval_bits(tcx, env)
+            mono_literal.try_eval_bits(tcx, typing_env)
         };
 
         let TerminatorKind::SwitchInt { discr, targets } = &block.terminator().kind else {