Rollup merge of #128720 - y21:issue119620, r=compiler-errors

Pass the right `ParamEnv` to `might_permit_raw_init_strict`

Fixes #119620

`might_permit_raw_init_strict` currently passes an empty `ParamEnv` to the `InterpCx`, instead of the actual `ParamEnv` that was passed in to `check_validity_requirement` at callsite.

This leads to ICEs such as the linked issue where for `UnsafeCell<*mut T>` we initially get the layout with the right `ParamEnv` (which suceeds because it can prove that `T: Sized` and therefore `UnsafeCell<*mut T>` has a known layout) but then do the rest with an empty `ParamEnv` where `T: Sized` is not known to hold so getting the layout for `*mut T` later fails.

This runs into an assertion in other layout code where it's making the (valid) assumption that, when we already have a layout for a struct (`UnsafeCell<*mut T>`), getting the layout of one of its fields (`*mut T`) should also succeed, which wasn't the case here due to using the wrong `ParamEnv`.

So, this PR changes it to just use the same `ParamEnv` all the way throughout.

1 files changed, 5 insertions, 5 deletions

diff --git a/compiler/rustc_const_eval/src/util/check_validity_requirement.rs b/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
index 4b6b1e453b8..cbd1fdeea2a 100644
--- a/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
+++ b/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
@@ -1,6 +1,6 @@
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{LayoutCx, LayoutError, LayoutOf, TyAndLayout, ValidityRequirement};
-use rustc_middle::ty::{ParamEnv, ParamEnvAnd, Ty, TyCtxt};
+use rustc_middle::ty::{ParamEnvAnd, Ty, TyCtxt};
 use rustc_target::abi::{Abi, FieldsShape, Scalar, Variants};
 
 use crate::const_eval::{CanAccessMutGlobal, CheckAlignment, CompileTimeMachine};
@@ -30,10 +30,10 @@ pub fn check_validity_requirement<'tcx>(
         return Ok(!layout.abi.is_uninhabited());
     }
 
+    let layout_cx = LayoutCx { tcx, param_env: param_env_and_ty.param_env };
     if kind == ValidityRequirement::Uninit || tcx.sess.opts.unstable_opts.strict_init_checks {
-        might_permit_raw_init_strict(layout, tcx, kind)
+        might_permit_raw_init_strict(layout, &layout_cx, kind)
     } else {
-        let layout_cx = LayoutCx { tcx, param_env: param_env_and_ty.param_env };
         might_permit_raw_init_lax(layout, &layout_cx, kind)
     }
 }
@@ -42,12 +42,12 @@ pub fn check_validity_requirement<'tcx>(
 /// details.
 fn might_permit_raw_init_strict<'tcx>(
     ty: TyAndLayout<'tcx>,
-    tcx: TyCtxt<'tcx>,
+    cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
     kind: ValidityRequirement,
 ) -> Result<bool, &'tcx LayoutError<'tcx>> {
     let machine = CompileTimeMachine::new(CanAccessMutGlobal::No, CheckAlignment::Error);
 
-    let mut cx = InterpCx::new(tcx, rustc_span::DUMMY_SP, ParamEnv::reveal_all(), machine);
+    let mut cx = InterpCx::new(cx.tcx, rustc_span::DUMMY_SP, cx.param_env, machine);
 
     let allocated = cx
         .allocate(ty, MemoryKind::Machine(crate::const_eval::MemoryKind::Heap))