Get rid of const eval_* and try_eval_* helpers

compiler-errors · compiler-errors · commit 5b906d51c88d · 2024-09-27T12:56:51.000-04:00
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/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.
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -1172,8 +1172,10 @@ 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())
-                        == Some(expected_bytes) =>
+                    && len
+                        .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);
@@ -1462,8 +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())
-                        == Some(expected_bytes) =>
+                    && len
+                        .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));
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
@@ -690,16 +690,20 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
                 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}")
                 }
                 _ => {
diff --git a/compiler/rustc_const_eval/src/const_eval/mod.rs b/compiler/rustc_const_eval/src/const_eval/mod.rs
@@ -55,7 +55,13 @@ 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)
+                .expect("expected monomorphic constant when printing MIR const")
+                as usize,
+            None,
+            op,
+        ),
         ty::Adt(def, _) if def.variants().is_empty() => {
             return None;
         }
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -394,7 +394,9 @@ 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)
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -1086,7 +1086,8 @@ 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())) {
+        // TODO:
+        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;
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
@@ -77,7 +77,8 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                 let (size, ty) = match elem_ty.kind() {
                     ty::Array(ty, len) => {
                         if let Some(len) =
-                            len.try_eval_target_usize(self.tcx, self.tcx.param_env(adt.did()))
+                            // TODO:
+                            len.try_to_target_usize(self.tcx)
                         {
                             (len, *ty)
                         } else {
diff --git a/compiler/rustc_lint/src/builtin.rs b/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 {
diff --git a/compiler/rustc_lint/src/unused.rs b/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.
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/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)
                     }
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
@@ -431,100 +431,47 @@ impl<'tcx> Const<'tcx> {
         }
     }
 
-    #[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> {
-        self.try_to_valtree()?.try_to_scalar()
+    pub fn try_to_scalar(self) -> Option<(Scalar, Ty<'tcx>)> {
+        let (valtree, ty) = self.try_to_valtree()?;
+        Some((valtree.try_to_scalar()?, ty))
     }
 
     pub fn try_to_bool(self) -> Option<bool> {
-        self.try_to_scalar()?.to_bool().ok()
+        self.try_to_scalar()?.0.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 {
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/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),
             },
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
@@ -387,7 +387,7 @@ 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));
                 }
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
@@ -1105,7 +1105,12 @@ 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]
diff --git a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs b/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),
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
@@ -18,6 +18,8 @@ struct MoveDataBuilder<'a, 'tcx, F> {
     body: &'a Body<'tcx>,
     loc: Location,
     tcx: TyCtxt<'tcx>,
+    // TODO:
+    #[allow(unused)]
     param_env: ty::ParamEnv<'tcx>,
     data: MoveData<'tcx>,
     filter: F,
@@ -549,7 +551,9 @@ 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 {
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/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
             })
         }
diff --git a/compiler/rustc_mir_transform/src/known_panics_lint.rs b/compiler/rustc_mir_transform/src/known_panics_lint.rs
@@ -605,7 +605,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                     Value::Immediate(src) => src.len(&self.ecx).ok()?,
                     Value::Aggregate { fields, .. } => fields.len() as u64,
                     Value::Uninit => match place.ty(self.local_decls(), self.tcx).ty.kind() {
-                        ty::Array(_, n) => n.try_eval_target_usize(self.tcx, self.param_env)?,
+                        ty::Array(_, n) => n.try_to_target_usize(self.tcx)?,
                         _ => return None,
                     },
                 };
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/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),
                     }
diff --git a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs
diff --git a/compiler/rustc_smir/src/rustc_smir/context.rs b/compiler/rustc_smir/src/rustc_smir/context.rs
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs

Original file line number	Diff line number	Diff line change
`@@ -1086,7 +1086,8 @@ fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {`
`1086`	`1086`	`return;`
`1087`	`1087`	`}`
`1088`	`1088`
`1089`		`- if let Some(len) = len_const.try_eval_target_usize(tcx, tcx.param_env(def.did())) {`
	`1089`	`+ // TODO:`
	`1090`	`+ if let Some(len) = len_const.try_to_target_usize(tcx) {`
`1090`	`1091`	`if len == 0 {`
`1091`	`1092`	`struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit();`
`1092`	`1093`	`return;`
Original file line number	Diff line number	Diff line change
`@@ -2601,7 +2601,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {`
`2601`	`2601`	`ty.tuple_fields().iter().find_map(\|field\| ty_find_init_error(cx, field, init))`
`2602`	`2602`	`}`
`2603`	`2603`	`Array(ty, len) => {`
`2604`		`- if matches!(len.try_eval_target_usize(cx.tcx, cx.param_env), Some(v) if v > 0) {`
	`2604`	`+ if matches!(len.try_to_target_usize(cx.tcx), Some(v) if v > 0) {`
`2605`	`2605`	`// Array length known at array non-empty -- recurse.`
`2606`	`2606`	`ty_find_init_error(cx, *ty, init)`
`2607`	`2607`	`} else {`
Original file line number	Diff line number	Diff line change
`@@ -346,7 +346,7 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {`
`346`	`346`	`None`
`347`	`347`	`}`
`348`	`348`	`}`
`349`		`- ty::Array(ty, len) => match len.try_eval_target_usize(cx.tcx, cx.param_env) {`
	`349`	`+ ty::Array(ty, len) => match len.try_to_target_usize(cx.tcx) {`
`350`	`350`	`// If the array is empty we don't lint, to avoid false positives`
`351`	`351`	`Some(0) \| None => None,`
`352`	`352`	// If the array is definitely non-empty, we can do `#[must_use]` checking.