Get rid of const eval_* and try_eval_* helpers

compiler/rustc_borrowck/src/lib.rs

@@ -187,10 +187,10 @@ fn do_mir_borrowck<'tcx>(
 
     let location_table = LocationTable::new(body);
 
-    let move_data = MoveData::gather_moves(body, tcx, param_env, |_| true);
+    let move_data = MoveData::gather_moves(body, tcx, |_| true);
     let promoted_move_data = promoted
         .iter_enumerated()
-        .map(|(idx, body)| (idx, MoveData::gather_moves(body, tcx, param_env, |_| true)));
+        .map(|(idx, body)| (idx, MoveData::gather_moves(body, tcx, |_| true)));
 
     let mut flow_inits = MaybeInitializedPlaces::new(tcx, body, &move_data)
         .into_engine(tcx, body)

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1128,7 +1128,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             }
             let projected_ty = curr_projected_ty.projection_ty_core(
                 tcx,
-                self.param_env,
                 proj,
                 |this, field, ()| {
                     let ty = this.field_ty(tcx, field);
@@ -1919,7 +1918,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 // than 1.
                 // If the length is larger than 1, the repeat expression will need to copy the
                 // element, so we require the `Copy` trait.
-                if len.try_eval_target_usize(tcx, self.param_env).map_or(true, |len| len > 1) {
+                if len.try_to_target_usize(tcx).is_none_or(|len| len > 1) {
                     match operand {
                         Operand::Copy(..) | Operand::Constant(..) => {
                             // These are always okay: direct use of a const, or a value that can evidently be copied.

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -1177,8 +1177,10 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             ty::Uint(i) if i.bit_width() == Some(expected_int_bits) => args[0].immediate(),
             ty::Array(elem, len)
                 if matches!(elem.kind(), ty::Uint(ty::UintTy::U8))
-                    && len.try_eval_target_usize(bx.tcx, ty::ParamEnv::reveal_all())
+                    && len
-                        == Some(expected_bytes) =>
+                        .try_to_target_usize(bx.tcx)
+                        .expect("expected monomorphic const in codegen")
+                        == expected_bytes =>
             {
                 let place = PlaceRef::alloca(bx, args[0].layout);
                 args[0].val.store(bx, place);
@@ -1243,12 +1245,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     }
 
     if name == sym::simd_shuffle_generic {
-        let idx = fn_args[2]
+        let idx = fn_args[2].expect_const().try_to_valtree().unwrap().0.unwrap_branch();
-            .expect_const()
-            .eval(tcx, ty::ParamEnv::reveal_all(), span)
-            .unwrap()
-            .1
-            .unwrap_branch();
         let n = idx.len() as u64;
 
         let (out_len, out_ty) = require_simd!(ret_ty, SimdReturn);
@@ -1467,8 +1464,10 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
             }
             ty::Array(elem, len)
                 if matches!(elem.kind(), ty::Uint(ty::UintTy::U8))
-                    && len.try_eval_target_usize(bx.tcx, ty::ParamEnv::reveal_all())
+                    && len
-                        == Some(expected_bytes) =>
+                        .try_to_target_usize(bx.tcx)
+                        .expect("expected monomorphic const in codegen")
+                        == expected_bytes =>
             {
                 // Zero-extend iN to the array length:
                 let ze = bx.zext(i_, bx.type_ix(expected_bytes * 8));

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -23,7 +23,6 @@ use rustc_middle::ty::layout::{IntegerExt, TyAndLayout};
 use rustc_middle::ty::{
     self, ExistentialProjection, GenericArgKind, GenericArgsRef, ParamEnv, Ty, TyCtxt,
 };
-use rustc_span::DUMMY_SP;
 use rustc_target::abi::Integer;
 use smallvec::SmallVec;
 
@@ -685,21 +684,25 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
         ty::ConstKind::Param(param) => {
             write!(output, "{}", param.name)
         }
-        ty::ConstKind::Value(ty, _) => {
+        ty::ConstKind::Value(ty, valtree) => {
             match ty.kind() {
                 ty::Int(ity) => {
                     // FIXME: directly extract the bits from a valtree instead of evaluating an
                     // already evaluated `Const` in order to get the bits.
-                    let bits = ct.eval_bits(tcx, ty::ParamEnv::reveal_all());
+                    let bits = ct
+                        .try_to_bits(tcx, ty::ParamEnv::reveal_all())
+                        .expect("expected monomorphic const in codegen");
                     let val = Integer::from_int_ty(&tcx, *ity).size().sign_extend(bits) as i128;
                     write!(output, "{val}")
                 }
                 ty::Uint(_) => {
-                    let val = ct.eval_bits(tcx, ty::ParamEnv::reveal_all());
+                    let val = ct
+                        .try_to_bits(tcx, ty::ParamEnv::reveal_all())
+                        .expect("expected monomorphic const in codegen");
                     write!(output, "{val}")
                 }
                 ty::Bool => {
-                    let val = ct.try_eval_bool(tcx, ty::ParamEnv::reveal_all()).unwrap();
+                    let val = ct.try_to_bool().expect("expected monomorphic const in codegen");
                     write!(output, "{val}")
                 }
                 _ => {
@@ -711,8 +714,9 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
                     // avoiding collisions and will make the emitted type names shorter.
                     let hash_short = tcx.with_stable_hashing_context(|mut hcx| {
                         let mut hasher = StableHasher::new();
-                        let ct = ct.eval(tcx, ty::ParamEnv::reveal_all(), DUMMY_SP).unwrap();
+                        hcx.while_hashing_spans(false, |hcx| {
-                        hcx.while_hashing_spans(false, |hcx| ct.hash_stable(hcx, &mut hasher));
+                            (ty, valtree).hash_stable(hcx, &mut hasher)
+                        });
                         hasher.finish::<Hash64>()
                     });
 

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -43,7 +43,7 @@ pub(crate) fn try_destructure_mir_constant_for_user_output<'tcx>(
 
     // We go to `usize` as we cannot allocate anything bigger anyway.
     let (field_count, variant, down) = match ty.kind() {
-        ty::Array(_, len) => (len.eval_target_usize(tcx.tcx, param_env) as usize, None, op),
+        ty::Array(_, len) => (len.try_to_target_usize(tcx.tcx)? as usize, None, op),
         ty::Adt(def, _) if def.variants().is_empty() => {
             return None;
         }

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -391,7 +391,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let ptr = self.read_pointer(src)?;
                 let val = Immediate::new_slice(
                     ptr,
-                    length.eval_target_usize(*self.tcx, self.param_env),
+                    length
+                        .try_to_target_usize(*self.tcx)
+                        .expect("expected monomorphic const in const eval"),
                     self,
                 );
                 self.write_immediate(val, dest)

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1037,7 +1037,11 @@ fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
             return;
         }
 
-        if let Some(len) = len_const.try_eval_target_usize(tcx, tcx.param_env(def.did())) {
+        // FIXME(repr_simd): This check is nice, but perhaps unnecessary due to the fact
+        // we do not expect users to implement their own `repr(simd)` types. If they could,
+        // this check is easily side-steppable by hiding the const behind normalization.
+        // The consequence is that the error is, in general, only observable post-mono.
+        if let Some(len) = len_const.try_to_target_usize(tcx) {
             if len == 0 {
                 struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit();
                 return;

compiler/rustc_hir_analysis/src/check/intrinsicck.rs

@@ -76,9 +76,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
 
                 let (size, ty) = match elem_ty.kind() {
                     ty::Array(ty, len) => {
-                        if let Some(len) =
+                        if let Some(len) = len.try_to_target_usize(self.tcx) {
-                            len.try_eval_target_usize(self.tcx, self.tcx.param_env(adt.did()))
-                        {
                             (len, *ty)
                         } else {
                             return None;

compiler/rustc_lint/src/builtin.rs

@@ -2601,7 +2601,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
                     ty.tuple_fields().iter().find_map(|field| ty_find_init_error(cx, field, init))
                 }
                 Array(ty, len) => {
-                    if matches!(len.try_eval_target_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {
+                    if matches!(len.try_to_target_usize(cx.tcx), Some(v) if v > 0) {
                         // Array length known at array non-empty -- recurse.
                         ty_find_init_error(cx, *ty, init)
                     } else {

compiler/rustc_lint/src/unused.rs

@@ -346,7 +346,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                         None
                     }
                 }
-                ty::Array(ty, len) => match len.try_eval_target_usize(cx.tcx, cx.param_env) {
+                ty::Array(ty, len) => match len.try_to_target_usize(cx.tcx) {
                     // If the array is empty we don't lint, to avoid false positives
                     Some(0) | None => None,
                     // If the array is definitely non-empty, we can do `#[must_use]` checking.

compiler/rustc_middle/src/mir/consts.rs

@@ -6,6 +6,7 @@ use rustc_session::RemapFileNameExt;
 use rustc_session::config::RemapPathScopeComponents;
 use rustc_span::{DUMMY_SP, Span};
 use rustc_target::abi::{HasDataLayout, Size};
+use either::Either;
 
 use crate::mir::interpret::{AllocId, ConstAllocation, ErrorHandled, Scalar, alloc_range};
 use crate::mir::{Promoted, pretty_print_const_value};
@@ -320,8 +321,14 @@ impl<'tcx> Const<'tcx> {
             Const::Ty(_, c) => {
                 // We want to consistently have a "clean" value for type system constants (i.e., no
                 // data hidden in the padding), so we always go through a valtree here.
-                let (ty, val) = c.eval(tcx, param_env, span)?;
+                match c.eval_valtree(tcx, param_env, span) {
-                Ok(tcx.valtree_to_const_val((ty, val)))
+                    Ok((ty, val)) => Ok(tcx.valtree_to_const_val((ty, val))),
+                    Err(Either::Left(_bad_ty)) => Err(tcx
+                        .dcx()
+                        .delayed_bug("`mir::Const::eval` called on a non-valtree-compatible type")
+                        .into()),
+                    Err(Either::Right(e)) => Err(e),
+                }
             }
             Const::Unevaluated(uneval, _) => {
                 // FIXME: We might want to have a `try_eval`-like function on `Unevaluated`

compiler/rustc_middle/src/mir/tcx.rs

@@ -55,7 +55,7 @@ impl<'tcx> PlaceTy<'tcx> {
     /// `PlaceElem`, where we can just use the `Ty` that is already
     /// stored inline on field projection elems.
     pub fn projection_ty(self, tcx: TyCtxt<'tcx>, elem: PlaceElem<'tcx>) -> PlaceTy<'tcx> {
-        self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty, |_, ty| ty)
+        self.projection_ty_core(tcx, &elem, |_, _, ty| ty, |_, ty| ty)
     }
 
     /// `place_ty.projection_ty_core(tcx, elem, |...| { ... })`
@@ -66,7 +66,6 @@ impl<'tcx> PlaceTy<'tcx> {
     pub fn projection_ty_core<V, T>(
         self,
         tcx: TyCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
         elem: &ProjectionElem<V, T>,
         mut handle_field: impl FnMut(&Self, FieldIdx, T) -> Ty<'tcx>,
         mut handle_opaque_cast_and_subtype: impl FnMut(&Self, T) -> Ty<'tcx>,
@@ -93,7 +92,9 @@ impl<'tcx> PlaceTy<'tcx> {
                     ty::Slice(..) => self.ty,
                     ty::Array(inner, _) if !from_end => Ty::new_array(tcx, *inner, to - from),
                     ty::Array(inner, size) if from_end => {
-                        let size = size.eval_target_usize(tcx, param_env);
+                        let size = size
+                            .try_to_target_usize(tcx)
+                            .expect("expected subslice projection on fixed-size array");
                         let len = size - from - to;
                         Ty::new_array(tcx, *inner, len)
                     }

compiler/rustc_middle/src/ty/consts.rs

@@ -398,133 +398,65 @@ impl<'tcx> Const<'tcx> {
         }
     }
 
-    /// Returns the evaluated constant
-    #[inline]
-    pub fn eval(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
-        span: Span,
-    ) -> Result<(Ty<'tcx>, ValTree<'tcx>), ErrorHandled> {
-        self.eval_valtree(tcx, param_env, span).map_err(|err| {
-            match err {
-                Either::Right(err) => err,
-                Either::Left(_bad_ty) => {
-                    // This can happen when we run on ill-typed code.
-                    let e = tcx.dcx().span_delayed_bug(
-                        span,
-                        "`ty::Const::eval` called on a non-valtree-compatible type",
-                    );
-                    e.into()
-                }
-            }
-        })
-    }
-
     /// Normalizes the constant to a value or an error if possible.
     #[inline]
     pub fn normalize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Self {
-        match self.eval(tcx, param_env, DUMMY_SP) {
+        match self.eval_valtree(tcx, param_env, DUMMY_SP) {
             Ok((ty, val)) => Self::new_value(tcx, val, ty),
-            Err(ErrorHandled::Reported(r, _span)) => Self::new_error(tcx, r.into()),
+            Err(Either::Left(_bad_ty)) => {
-            Err(ErrorHandled::TooGeneric(_span)) => self,
+                // This can happen when we run on ill-typed code.
+                Self::new_error(
+                    tcx,
+                    tcx.dcx()
+                        .delayed_bug("`ty::Const::eval` called on a non-valtree-compatible type"),
+                )
             }
+            Err(Either::Right(ErrorHandled::Reported(r, _span))) => Self::new_error(tcx, r.into()),
+            Err(Either::Right(ErrorHandled::TooGeneric(_span))) => self,
         }
-
-    #[inline]
-    pub fn try_eval_scalar(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-    ) -> Option<(Ty<'tcx>, Scalar)> {
-        let (ty, val) = self.eval(tcx, param_env, DUMMY_SP).ok()?;
-        let val = val.try_to_scalar()?;
-        Some((ty, val))
-    }
-
-    #[inline]
-    /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of
-    /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it
-    /// contains const generic parameters or pointers).
-    pub fn try_eval_scalar_int(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
-    ) -> Option<(Ty<'tcx>, ScalarInt)> {
-        let (ty, scalar) = self.try_eval_scalar(tcx, param_env)?;
-        let val = scalar.try_to_scalar_int().ok()?;
-        Some((ty, val))
-    }
-
-    #[inline]
-    /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of
-    /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it
-    /// contains const generic parameters or pointers).
-    pub fn try_eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u128> {
-        let (ty, scalar) = self.try_eval_scalar_int(tcx, param_env)?;
-        let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
-        // if `ty` does not depend on generic parameters, use an empty param_env
-        Some(scalar.to_bits(size))
-    }
-
-    #[inline]
-    /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
-    pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u128 {
-        self.try_eval_bits(tcx, param_env)
-            .unwrap_or_else(|| bug!("failed to evalate {:#?} to bits", self))
-    }
-
-    #[inline]
-    pub fn try_eval_target_usize(
-        self,
-        tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
-    ) -> Option<u64> {
-        let (_, scalar) = self.try_eval_scalar_int(tcx, param_env)?;
-        Some(scalar.to_target_usize(tcx))
-    }
-
-    #[inline]
-    pub fn try_eval_bool(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<bool> {
-        let (_, scalar) = self.try_eval_scalar_int(tcx, param_env)?;
-        scalar.try_into().ok()
-    }
-
-    #[inline]
-    /// Panics if the value cannot be evaluated or doesn't contain a valid `usize`.
-    pub fn eval_target_usize(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u64 {
-        self.try_eval_target_usize(tcx, param_env)
-            .unwrap_or_else(|| bug!("expected usize, got {:#?}", self))
     }
 
     /// Panics if self.kind != ty::ConstKind::Value
-    pub fn to_valtree(self) -> ty::ValTree<'tcx> {
+    pub fn to_valtree(self) -> (ty::ValTree<'tcx>, Ty<'tcx>) {
         match self.kind() {
-            ty::ConstKind::Value(_, valtree) => valtree,
+            ty::ConstKind::Value(ty, valtree) => (valtree, ty),
             _ => bug!("expected ConstKind::Value, got {:?}", self.kind()),
         }
     }
 
     /// Attempts to convert to a `ValTree`
-    pub fn try_to_valtree(self) -> Option<ty::ValTree<'tcx>> {
+    pub fn try_to_valtree(self) -> Option<(ty::ValTree<'tcx>, Ty<'tcx>)> {
         match self.kind() {
-            ty::ConstKind::Value(_, valtree) => Some(valtree),
+            ty::ConstKind::Value(ty, valtree) => Some((valtree, ty)),
             _ => None,
         }
     }
 
     #[inline]
-    pub fn try_to_scalar(self) -> Option<Scalar> {
+    pub fn try_to_scalar(self) -> Option<(Scalar, Ty<'tcx>)> {
-        self.try_to_valtree()?.try_to_scalar()
+        let (valtree, ty) = self.try_to_valtree()?;
+        Some((valtree.try_to_scalar()?, ty))
     }
 
     pub fn try_to_bool(self) -> Option<bool> {
-        self.try_to_valtree()?.try_to_scalar_int()?.try_to_bool().ok()
+        self.try_to_valtree()?.0.try_to_scalar_int()?.try_to_bool().ok()
     }
 
     #[inline]
     pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64> {
-        self.try_to_valtree()?.try_to_target_usize(tcx)
+        self.try_to_valtree()?.0.try_to_target_usize(tcx)
+    }
+
+    #[inline]
+    /// Attempts to evaluate the given constant to bits. Can fail to evaluate in the presence of
+    /// generics (or erroneous code) or if the value can't be represented as bits (e.g. because it
+    /// contains const generic parameters or pointers).
+    pub fn try_to_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> Option<u128> {
+        let (scalar, ty) = self.try_to_scalar()?;
+        let scalar = scalar.try_to_scalar_int().ok()?;
+        let size = tcx.layout_of(param_env.with_reveal_all_normalized(tcx).and(ty)).ok()?.size;
+        // if `ty` does not depend on generic parameters, use an empty param_env
+        Some(scalar.to_bits(size))
     }
 
     pub fn is_ct_infer(self) -> bool {

compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs

@@ -85,7 +85,7 @@ impl<'tcx> InhabitedPredicate<'tcx> {
         match self {
             Self::False => Ok(false),
             Self::True => Ok(true),
-            Self::ConstIsZero(const_) => match const_.try_eval_target_usize(tcx, param_env) {
+            Self::ConstIsZero(const_) => match const_.try_to_target_usize(tcx) {
                 None | Some(0) => Ok(true),
                 Some(1..) => Ok(false),
             },

compiler/rustc_middle/src/ty/layout.rs

@@ -397,7 +397,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                 }
             }
             ty::Array(inner, len) if tcx.features().transmute_generic_consts => {
-                let len_eval = len.try_eval_target_usize(tcx, param_env);
+                let len_eval = len.try_to_target_usize(tcx);
                 if len_eval == Some(0) {
                     return Ok(SizeSkeleton::Known(Size::from_bytes(0), None));
                 }

compiler/rustc_middle/src/ty/sty.rs

@@ -1117,7 +1117,12 @@ impl<'tcx> Ty<'tcx> {
         // The way we evaluate the `N` in `[T; N]` here only works since we use
         // `simd_size_and_type` post-monomorphization. It will probably start to ICE
         // if we use it in generic code. See the `simd-array-trait` ui test.
-        (f0_len.eval_target_usize(tcx, ParamEnv::empty()), *f0_elem_ty)
+        (
+            f0_len
+                .try_to_target_usize(tcx)
+                .expect("expected SIMD field to have definite array size"),
+            *f0_elem_ty,
+        )
     }
 
     #[inline]

compiler/rustc_mir_dataflow/src/elaborate_drops.rs

@@ -863,7 +863,7 @@ where
             ty::Adt(def, args) => self.open_drop_for_adt(*def, args),
             ty::Dynamic(..) => self.complete_drop(self.succ, self.unwind),
             ty::Array(ety, size) => {
-                let size = size.try_eval_target_usize(self.tcx(), self.elaborator.param_env());
+                let size = size.try_to_target_usize(self.tcx());
                 self.open_drop_for_array(*ety, size)
             }
             ty::Slice(ety) => self.drop_loop_pair(*ety),

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -18,18 +18,12 @@ struct MoveDataBuilder<'a, 'tcx, F> {
     body: &'a Body<'tcx>,
     loc: Location,
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     data: MoveData<'tcx>,
     filter: F,
 }
 
 impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
-    fn new(
+    fn new(body: &'a Body<'tcx>, tcx: TyCtxt<'tcx>, filter: F) -> Self {
-        body: &'a Body<'tcx>,
-        tcx: TyCtxt<'tcx>,
-        param_env: ty::ParamEnv<'tcx>,
-        filter: F,
-    ) -> Self {
         let mut move_paths = IndexVec::new();
         let mut path_map = IndexVec::new();
         let mut init_path_map = IndexVec::new();
@@ -59,7 +53,6 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             body,
             loc: Location::START,
             tcx,
-            param_env,
             data: MoveData {
                 moves: IndexVec::new(),
                 loc_map: LocationMap::new(body),
@@ -308,10 +301,9 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
 pub(super) fn gather_moves<'tcx>(
     body: &Body<'tcx>,
     tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     filter: impl Fn(Ty<'tcx>) -> bool,
 ) -> MoveData<'tcx> {
-    let mut builder = MoveDataBuilder::new(body, tcx, param_env, filter);
+    let mut builder = MoveDataBuilder::new(body, tcx, filter);
 
     builder.gather_args();
 
@@ -550,7 +542,9 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             };
             let base_ty = base_place.ty(self.body, self.tcx).ty;
             let len: u64 = match base_ty.kind() {
-                ty::Array(_, size) => size.eval_target_usize(self.tcx, self.param_env),
+                ty::Array(_, size) => size
+                    .try_to_target_usize(self.tcx)
+                    .expect("expected subslice projection on fixed-size array"),
                 _ => bug!("from_end: false slice pattern of non-array type"),
             };
             for offset in from..to {

compiler/rustc_mir_dataflow/src/move_paths/mod.rs

@@ -4,7 +4,7 @@ use std::ops::{Index, IndexMut};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::*;
-use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
+use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_span::Span;
 use smallvec::SmallVec;
 
@@ -352,10 +352,9 @@ impl<'tcx> MoveData<'tcx> {
     pub fn gather_moves(
         body: &Body<'tcx>,
         tcx: TyCtxt<'tcx>,
-        param_env: ParamEnv<'tcx>,
         filter: impl Fn(Ty<'tcx>) -> bool,
     ) -> MoveData<'tcx> {
-        builder::gather_moves(body, tcx, param_env, filter)
+        builder::gather_moves(body, tcx, filter)
     }
 
     /// For the move path `mpi`, returns the root local variable that starts the path.

compiler/rustc_mir_dataflow/src/rustc_peek.rs

@@ -40,8 +40,7 @@ pub fn sanity_check<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
         debug!("running rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
     }
 
-    let param_env = tcx.param_env(def_id);
+    let move_data = MoveData::gather_moves(body, tcx, |_| true);
-    let move_data = MoveData::gather_moves(body, tcx, param_env, |_| true);
 
     if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_maybe_init).is_some() {
         let flow_inits = MaybeInitializedPlaces::new(tcx, body, &move_data)

compiler/rustc_mir_transform/src/coroutine.rs

@@ -1957,7 +1957,8 @@ fn check_must_not_suspend_ty<'tcx>(
             let descr_pre = &format!("{}array{} of ", data.descr_pre, plural_suffix);
             check_must_not_suspend_ty(tcx, ty, hir_id, param_env, SuspendCheckData {
                 descr_pre,
-                plural_len: len.try_eval_target_usize(tcx, param_env).unwrap_or(0) as usize + 1,
+                // FIXME(must_not_suspend): This is wrong. We should handle printing unevaluated consts.
+                plural_len: len.try_to_target_usize(tcx).unwrap_or(0) as usize + 1,
                 ..data
             })
         }

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -58,8 +58,7 @@ impl<'tcx> crate::MirPass<'tcx> for ElaborateDrops {
         let param_env = tcx.param_env_reveal_all_normalized(def_id);
         // For types that do not need dropping, the behaviour is trivial. So we only need to track
         // init/uninit for types that do need dropping.
-        let move_data =
+        let move_data = MoveData::gather_moves(body, tcx, |ty| ty.needs_drop(tcx, param_env));
-            MoveData::gather_moves(body, tcx, param_env, |ty| ty.needs_drop(tcx, param_env));
         let elaborate_patch = {
             let env = MoveDataParamEnv { move_data, param_env };
 

compiler/rustc_mir_transform/src/known_panics_lint.rs

@@ -602,7 +602,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             Len(place) => {
                 let len = if let ty::Array(_, n) = place.ty(self.local_decls(), self.tcx).ty.kind()
                 {
-                    n.try_eval_target_usize(self.tcx, self.param_env)?
+                    n.try_to_target_usize(self.tcx)?
                 } else {
                     match self.get_const(place)? {
                         Value::Immediate(src) => src.len(&self.ecx).discard_err()?,

compiler/rustc_mir_transform/src/promote_consts.rs

@@ -329,7 +329,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                     // Determine the type of the thing we are indexing.
                     && let ty::Array(_, len) = place_base.ty(self.body, self.tcx).ty.kind()
                     // It's an array; determine its length.
-                    && let Some(len) = len.try_eval_target_usize(self.tcx, self.param_env)
+                    && let Some(len) = len.try_to_target_usize(self.tcx)
                     // If the index is in-bounds, go ahead.
                     && idx < len
                 {
@@ -407,7 +407,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                 // mutably without consequences. However, only &mut []
                 // is allowed right now.
                 if let ty::Array(_, len) = ty.kind() {
-                    match len.try_eval_target_usize(self.tcx, self.param_env) {
+                    match len.try_to_target_usize(self.tcx) {
                         Some(0) => {}
                         _ => return Err(Unpromotable),
                     }

compiler/rustc_mir_transform/src/remove_uninit_drops.rs

@@ -19,8 +19,7 @@ pub(super) struct RemoveUninitDrops;
 impl<'tcx> crate::MirPass<'tcx> for RemoveUninitDrops {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let param_env = tcx.param_env(body.source.def_id());
-        let move_data =
+        let move_data = MoveData::gather_moves(body, tcx, |ty| ty.needs_drop(tcx, param_env));
-            MoveData::gather_moves(body, tcx, param_env, |ty| ty.needs_drop(tcx, param_env));
 
         let mut maybe_inits = MaybeInitializedPlaces::new(tcx, body, &move_data)
             .into_engine(tcx, body)

compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs

@@ -133,7 +133,9 @@ fn encode_const<'tcx>(
             // bool value false is encoded as 0 and true as 1.
             match ct_ty.kind() {
                 ty::Int(ity) => {
-                    let bits = c.eval_bits(tcx, ty::ParamEnv::reveal_all());
+                    let bits = c
+                        .try_to_bits(tcx, ty::ParamEnv::reveal_all())
+                        .expect("expected monomorphic const in cfi");
                     let val = Integer::from_int_ty(&tcx, *ity).size().sign_extend(bits) as i128;
                     if val < 0 {
                         s.push('n');
@@ -141,7 +143,9 @@ fn encode_const<'tcx>(
                     let _ = write!(s, "{val}");
                 }
                 ty::Uint(_) => {
-                    let val = c.eval_bits(tcx, ty::ParamEnv::reveal_all());
+                    let val = c
+                        .try_to_bits(tcx, ty::ParamEnv::reveal_all())
+                        .expect("expected monomorphic const in cfi");
                     let _ = write!(s, "{val}");
                 }
                 ty::Bool => {

compiler/rustc_smir/src/rustc_smir/context.rs

@@ -406,7 +406,7 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         let tcx = tables.tcx;
         let mir_const = cnst.internal(&mut *tables, tcx);
         mir_const
-            .try_eval_target_usize(tables.tcx, ParamEnv::empty())
+            .try_to_target_usize(tables.tcx)
             .ok_or_else(|| Error::new(format!("Const `{cnst:?}` cannot be encoded as u64")))
     }
 

compiler/rustc_symbol_mangling/src/v0.rs

@@ -592,7 +592,9 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
             ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => {
                 ct_ty.print(self)?;
 
-                let mut bits = ct.eval_bits(self.tcx, ty::ParamEnv::reveal_all());
+                let mut bits = ct
+                    .try_to_bits(self.tcx, ty::ParamEnv::reveal_all())
+                    .expect("expected const to be monomorphic");
 
                 // Negative integer values are mangled using `n` as a "sign prefix".
                 if let ty::Int(ity) = ct_ty.kind() {

compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs

@@ -231,7 +231,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             // Arrays give us `[]`, `[{ty}; _]` and `[{ty}; N]`
             if let ty::Array(aty, len) = self_ty.kind() {
                 flags.push((sym::_Self, Some("[]".to_string())));
-                let len = len.try_to_valtree().and_then(|v| v.try_to_target_usize(self.tcx));
+                let len = len.try_to_target_usize(self.tcx);
                 flags.push((sym::_Self, Some(format!("[{aty}; _]"))));
                 if let Some(n) = len {
                     flags.push((sym::_Self, Some(format!("[{aty}; {n}]"))));

compiler/rustc_transmute/src/lib.rs

@@ -85,7 +85,6 @@ mod rustc {
     use rustc_macros::TypeVisitable;
     use rustc_middle::traits::ObligationCause;
     use rustc_middle::ty::{Const, ParamEnv, Ty, TyCtxt, ValTree};
-    use rustc_span::DUMMY_SP;
 
     use super::*;
 
@@ -134,7 +133,7 @@ mod rustc {
             use rustc_middle::ty::ScalarInt;
             use rustc_span::symbol::sym;
 
-            let Ok((ty, cv)) = c.eval(tcx, param_env, DUMMY_SP) else {
+            let Some((cv, ty)) = c.try_to_valtree() else {
                 return Some(Self {
                     alignment: true,
                     lifetimes: true,

compiler/rustc_ty_utils/src/layout.rs

@@ -170,12 +170,12 @@ fn layout_of_uncached<'tcx>(
                     if let Abi::Scalar(scalar) | Abi::ScalarPair(scalar, _) = &mut layout.abi {
                         if let Some(start) = start {
                             scalar.valid_range_mut().start = start
-                                .try_eval_bits(tcx, param_env)
+                                .try_to_bits(tcx, param_env)
                                 .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
                         }
                         if let Some(end) = end {
                             let mut end = end
-                                .try_eval_bits(tcx, param_env)
+                                .try_to_bits(tcx, param_env)
                                 .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
                             if !include_end {
                                 end = end.wrapping_sub(1);
@@ -315,7 +315,7 @@ fn layout_of_uncached<'tcx>(
             }
 
             let count = count
-                .try_eval_target_usize(tcx, param_env)
+                .try_to_target_usize(tcx)
                 .ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
             let element = cx.layout_of(element)?;
             let size = element