Auto merge of #132460 - lcnr:questionable-uwu, r=compiler-errors

Use `TypingMode` throughout the compiler instead of `ParamEnv`

Hopefully the biggest single PR as part of https://github.com/rust-lang/types-team/issues/128.

## `infcx.typing_env` while defining opaque types

I don't know how'll be able to correctly handle opaque types when using something taking a `TypingEnv` while defining opaque types. To correctly handle the opaques we need to be able to pass in the current `opaque_type_storage` and return constraints, i.e. we need to use a proper canonical query. We should migrate all the queries used during HIR typeck and borrowck where this matters to proper canonical queries. This is

## `layout_of` and `Reveal::All`

We convert the `ParamEnv` to `Reveal::All` right at the start of the `layout_of` query, so I've changed callers of `layout_of` to already use a post analysis `TypingEnv` when encountering it.

https://github.com/rust-lang/rust/blob/ca87b535a05097df6abbe2a031b057de2cefac5b/compiler/rustc_ty_utils/src/layout.rs#L51

## `Ty::is_[unpin|sized|whatever]`

I haven't migrated `fn is_item_raw` to use `TypingEnv`, will do so in a followup PR, this should significantly reduce the amount of `typing_env.param_env`. At some point there will probably be zero such uses as using the type system while ignoring the `typing_mode` is incorrect.

## `MirPhase` and phase-transitions

When inside of a MIR-body, we can mostly use its `MirPhase` to figure out the right `typing_mode`. This does not work during phase transitions, most notably when transitioning from `Analysis` to `Runtime`:

https://github.com/rust-lang/rust/blob/dae7ac133b9eda152784c075facb31a6688c92b1/compiler/rustc_mir_transform/src/lib.rs#L606-L625

All these passes still run with `MirPhase::Analysis`, but we should only use `Reveal::All` once we're run the `RevealAll` pass. This required me to manually construct the right `TypingEnv` in all these passes. Given that it feels somewhat easy to accidentally miss this going forward, I would maybe like to change `Body::phase` to an `Option` and replace it at the start of phase transitions. This then makes it clear that the MIR is currently in a weird state.

r? `@ghost`

3 files changed, 13 insertions, 7 deletions

diff --git a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
index a430d9dc797..ca3ee6773a0 100644
--- a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
@@ -221,7 +221,7 @@ pub(super) fn op_to_const<'tcx>(
                 let pointee_ty = imm.layout.ty.builtin_deref(false).unwrap(); // `false` = no raw ptrs
                 debug_assert!(
                     matches!(
-                        ecx.tcx.struct_tail_for_codegen(pointee_ty, ecx.param_env).kind(),
+                        ecx.tcx.struct_tail_for_codegen(pointee_ty, ecx.typing_env()).kind(),
                         ty::Str | ty::Slice(..),
                     ),
                     "`ConstValue::Slice` is for slice-tailed types only, but got {}",
@@ -280,11 +280,13 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
     // opaque types. This is needed for trivial things like `size_of`, but also for using associated
     // types that are not specified in the opaque type.
     assert_eq!(key.param_env.reveal(), Reveal::All);
+    let typing_env =
+        ty::TypingEnv { typing_mode: ty::TypingMode::PostAnalysis, param_env: key.param_env };
 
     // We call `const_eval` for zero arg intrinsics, too, in order to cache their value.
     // Catch such calls and evaluate them instead of trying to load a constant's MIR.
     if let ty::InstanceKind::Intrinsic(def_id) = key.value.instance.def {
-        let ty = key.value.instance.ty(tcx, key.param_env);
+        let ty = key.value.instance.ty(tcx, typing_env);
         let ty::FnDef(_, args) = ty.kind() else {
             bug!("intrinsic with type {:?}", ty);
         };
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index f12320cb851..19c3195aaa4 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -249,9 +249,10 @@ impl<'tcx> CompileTimeInterpCx<'tcx> {
         } else if self.tcx.is_lang_item(def_id, LangItem::PanicFmt) {
             // For panic_fmt, call const_panic_fmt instead.
             let const_def_id = self.tcx.require_lang_item(LangItem::ConstPanicFmt, None);
+            // FIXME(@lcnr): why does this use an empty env if we've got a `param_env` right here.
             let new_instance = ty::Instance::expect_resolve(
                 *self.tcx,
-                ty::ParamEnv::reveal_all(),
+                ty::TypingEnv::fully_monomorphized(),
                 const_def_id,
                 instance.args,
                 self.cur_span(),
diff --git a/compiler/rustc_const_eval/src/const_eval/valtrees.rs b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
index ea88b2ed22e..64bedea3b3f 100644
--- a/compiler/rustc_const_eval/src/const_eval/valtrees.rs
+++ b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
@@ -2,6 +2,7 @@ use rustc_abi::{BackendRepr, VariantIdx};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_middle::mir::interpret::{EvalToValTreeResult, GlobalId};
 use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
+use rustc_middle::ty::solve::Reveal;
 use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt};
 use rustc_middle::{bug, mir};
 use rustc_span::DUMMY_SP;
@@ -281,8 +282,9 @@ pub fn valtree_to_const_value<'tcx>(
     // the `ValTree` and using `place_projection` and `place_field` to
     // create inner `MPlace`s which are filled recursively.
     // FIXME Does this need an example?
-
     let (param_env, ty) = param_env_ty.into_parts();
+    debug_assert_eq!(param_env.reveal(), Reveal::All);
+    let typing_env = ty::TypingEnv { typing_mode: ty::TypingMode::PostAnalysis, param_env };
 
     match *ty.kind() {
         ty::FnDef(..) => {
@@ -302,11 +304,12 @@ pub fn valtree_to_const_value<'tcx>(
             let mut ecx =
                 mk_eval_cx_to_read_const_val(tcx, DUMMY_SP, param_env, CanAccessMutGlobal::No);
             let imm = valtree_to_ref(&mut ecx, valtree, inner_ty);
-            let imm = ImmTy::from_immediate(imm, tcx.layout_of(param_env_ty).unwrap());
+            let imm =
+                ImmTy::from_immediate(imm, tcx.layout_of(typing_env.as_query_input(ty)).unwrap());
             op_to_const(&ecx, &imm.into(), /* for diagnostics */ false)
         }
         ty::Tuple(_) | ty::Array(_, _) | ty::Adt(..) => {
-            let layout = tcx.layout_of(param_env_ty).unwrap();
+            let layout = tcx.layout_of(typing_env.as_query_input(ty)).unwrap();
             if layout.is_zst() {
                 // Fast path to avoid some allocations.
                 return mir::ConstValue::ZeroSized;
@@ -319,7 +322,7 @@ pub fn valtree_to_const_value<'tcx>(
                 let branches = valtree.unwrap_branch();
                 // Find the non-ZST field. (There can be aligned ZST!)
                 for (i, &inner_valtree) in branches.iter().enumerate() {
-                    let field = layout.field(&LayoutCx::new(tcx, param_env), i);
+                    let field = layout.field(&LayoutCx::new(tcx, typing_env), i);
                     if !field.is_zst() {
                         return valtree_to_const_value(tcx, param_env.and(field.ty), inner_valtree);
                     }