Remove is_normalizable. Add sizedness_of to avoid layout_of query on type aliases.

Author: Jarcho

clippy_lints/src/transmute/eager_transmute.rs

@@ -1,5 +1,4 @@
 use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::ty::is_normalizable;
 use clippy_utils::{eq_expr_value, path_to_local};
 use rustc_abi::WrappingRange;
 use rustc_errors::Applicability;
@@ -84,8 +83,6 @@ pub(super) fn check<'tcx>(
         && path.ident.name == sym!(then_some)
         && is_local_with_projections(transmutable)
         && binops_with_local(cx, transmutable, receiver)
-        && is_normalizable(cx, cx.param_env, from_ty)
-        && is_normalizable(cx, cx.param_env, to_ty)
         // we only want to lint if the target type has a niche that is larger than the one of the source type
         // e.g. `u8` to `NonZero<u8>` should lint, but `NonZero<u8>` to `u8` should not
         && let Ok(from_layout) = cx.tcx.layout_of(cx.param_env.and(from_ty))

clippy_lints/src/zero_sized_map_values.rs

@@ -1,10 +1,9 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::ty::{is_normalizable, is_type_diagnostic_item};
+use clippy_utils::ty::{is_type_diagnostic_item, sizedness_of};
 use rustc_hir::{self as hir, HirId, ItemKind, Node};
 use rustc_hir_analysis::lower_ty;
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::layout::LayoutOf as _;
-use rustc_middle::ty::{self, Ty, TypeVisitableExt};
+use rustc_middle::ty::{self, Ty};
 use rustc_session::declare_lint_pass;
 use rustc_span::sym;
 
@@ -51,13 +50,7 @@ impl LateLintPass<'_> for ZeroSizedMapValues {
             && (is_type_diagnostic_item(cx, ty, sym::HashMap) || is_type_diagnostic_item(cx, ty, sym::BTreeMap))
             && let ty::Adt(_, args) = ty.kind()
             && let ty = args.type_at(1)
-            // Fixes https://github.com/rust-lang/rust-clippy/issues/7447 because of
-            // https://github.com/rust-lang/rust/blob/master/compiler/rustc_middle/src/ty/sty.rs#L968
-            && !ty.has_escaping_bound_vars()
-            // Do this to prevent `layout_of` crashing, being unable to fully normalize `ty`.
-            && is_normalizable(cx, cx.param_env, ty)
-            && let Ok(layout) = cx.layout_of(ty)
-            && layout.is_zst()
+            && sizedness_of(cx.tcx, cx.param_env, ty).is_zero()
         {
             span_lint_and_help(
                 cx,

clippy_utils/src/ty.rs

@@ -15,7 +15,7 @@ use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::ConstValue;
 use rustc_middle::traits::EvaluationResult;
-use rustc_middle::ty::layout::ValidityRequirement;
+use rustc_middle::ty::layout::{LayoutOf, ValidityRequirement};
 use rustc_middle::ty::{
     self, AdtDef, AliasTy, AssocItem, AssocKind, Binder, BoundRegion, FnSig, GenericArg, GenericArgKind,
     GenericArgsRef, GenericParamDefKind, IntTy, ParamEnv, Region, RegionKind, TraitRef, Ty, TyCtxt, TypeSuperVisitable,
@@ -353,50 +353,6 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
     }
 }
 
-// FIXME: Per https://doc.rust-lang.org/nightly/nightly-rustc/rustc_trait_selection/infer/at/struct.At.html#method.normalize
-// this function can be removed once the `normalize` method does not panic when normalization does
-// not succeed
-/// Checks if `Ty` is normalizable. This function is useful
-/// to avoid crashes on `layout_of`.
-pub fn is_normalizable<'tcx>(cx: &LateContext<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
-    is_normalizable_helper(cx, param_env, ty, &mut FxHashMap::default())
-}
-
-fn is_normalizable_helper<'tcx>(
-    cx: &LateContext<'tcx>,
-    param_env: ParamEnv<'tcx>,
-    ty: Ty<'tcx>,
-    cache: &mut FxHashMap<Ty<'tcx>, bool>,
-) -> bool {
-    if let Some(&cached_result) = cache.get(&ty) {
-        return cached_result;
-    }
-    // prevent recursive loops, false-negative is better than endless loop leading to stack overflow
-    cache.insert(ty, false);
-    let infcx = cx.tcx.infer_ctxt().build();
-    let cause = ObligationCause::dummy();
-    let result = if infcx.at(&cause, param_env).query_normalize(ty).is_ok() {
-        match ty.kind() {
-            ty::Adt(def, args) => def.variants().iter().all(|variant| {
-                variant
-                    .fields
-                    .iter()
-                    .all(|field| is_normalizable_helper(cx, param_env, field.ty(cx.tcx, args), cache))
-            }),
-            _ => ty.walk().all(|generic_arg| match generic_arg.unpack() {
-                GenericArgKind::Type(inner_ty) if inner_ty != ty => {
-                    is_normalizable_helper(cx, param_env, inner_ty, cache)
-                },
-                _ => true, // if inner_ty == ty, we've already checked it
-            }),
-        }
-    } else {
-        false
-    };
-    cache.insert(ty, result);
-    result
-}
-
 /// Returns `true` if the given type is a non aggregate primitive (a `bool` or `char`, any
 /// integer or floating-point number type). For checking aggregation of primitive types (e.g.
 /// tuples and slices of primitive type) see `is_recursively_primitive_type`
@@ -977,11 +933,12 @@ pub fn adt_and_variant_of_res<'tcx>(cx: &LateContext<'tcx>, res: Res) -> Option<
 
 /// Comes up with an "at least" guesstimate for the type's size, not taking into
 /// account the layout of type parameters.
+///
+/// This function will ICE if called with an improper `ParamEnv`. This can happen
+/// when linting in when item, but the type is retrieved from a different item
+/// without instantiating the generic arguments. It can also happen when linting a
+/// type alias as those do not have a `ParamEnv`.
 pub fn approx_ty_size<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> u64 {
-    use rustc_middle::ty::layout::LayoutOf;
-    if !is_normalizable(cx, cx.param_env, ty) {
-        return 0;
-    }
     match (cx.layout_of(ty).map(|layout| layout.size.bytes()), ty.kind()) {
         (Ok(size), _) => size,
         (Err(_), ty::Tuple(list)) => list.iter().map(|t| approx_ty_size(cx, t)).sum(),
@@ -1340,3 +1297,91 @@ pub fn get_field_by_name<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, name: Symbol) ->
         _ => None,
     }
 }
+
+#[derive(Clone, Copy)]
+pub enum Sizedness {
+    /// The type is uninhabited. (e.g. `!`)
+    Uninhabited,
+    /// The type is zero-sized.
+    Zero,
+    /// The type has some other size or an unknown size.
+    Other,
+}
+impl Sizedness {
+    pub fn is_zero(self) -> bool {
+        matches!(self, Self::Zero)
+    }
+
+    pub fn is_uninhabited(self) -> bool {
+        matches!(self, Self::Uninhabited)
+    }
+}
+
+/// Calculates the sizedness of a type.
+pub fn sizedness_of<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> Sizedness {
+    fn is_zst<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
+        match *ty.kind() {
+            ty::FnDef(..) | ty::Never => true,
+            ty::Tuple(tys) => tys.iter().all(|ty| is_zst(tcx, param_env, ty)),
+            // Zero length arrays are always zero-sized, even for uninhabited types.
+            ty::Array(_, len) if len.try_eval_target_usize(tcx, param_env).is_some_and(|x| x == 0) => true,
+            ty::Array(ty, _) | ty::Pat(ty, _) => is_zst(tcx, param_env, ty),
+            ty::Adt(adt, args) => {
+                let mut iter = adt.variants().iter().filter(|v| {
+                    !v.fields
+                        .iter()
+                        .any(|f| f.ty(tcx, args).is_privately_uninhabited(tcx, param_env))
+                });
+                let is_zst = iter.next().map_or(true, |v| {
+                    v.fields.iter().all(|f| is_zst(tcx, param_env, f.ty(tcx, args)))
+                });
+                is_zst && iter.next().is_none()
+            },
+            ty::Closure(_, args) => args
+                .as_closure()
+                .upvar_tys()
+                .iter()
+                .all(|ty| is_zst(tcx, param_env, ty)),
+            ty::CoroutineWitness(_, args) => args
+                .iter()
+                .filter_map(GenericArg::as_type)
+                .all(|ty| is_zst(tcx, param_env, ty)),
+            ty::Alias(..) => {
+                if let Ok(normalized) = tcx.try_normalize_erasing_regions(param_env, ty)
+                    && normalized != ty
+                {
+                    is_zst(tcx, param_env, normalized)
+                } else {
+                    false
+                }
+            },
+            ty::Bool
+            | ty::Char
+            | ty::Int(_)
+            | ty::Uint(_)
+            | ty::Float(_)
+            | ty::RawPtr(..)
+            | ty::Ref(..)
+            | ty::FnPtr(..)
+            | ty::Param(_)
+            | ty::Bound(..)
+            | ty::Placeholder(_)
+            | ty::Infer(_)
+            | ty::Error(_)
+            | ty::Dynamic(..)
+            | ty::Slice(..)
+            | ty::Str
+            | ty::Foreign(_)
+            | ty::Coroutine(..)
+            | ty::CoroutineClosure(..) => false,
+        }
+    }
+
+    if ty.is_privately_uninhabited(tcx, param_env) {
+        Sizedness::Uninhabited
+    } else if is_zst(tcx, param_env, ty) {
+        Sizedness::Zero
+    } else {
+        Sizedness::Other
+    }
+}

tests/ui/crashes/ice-10508.rs

@@ -0,0 +1,19 @@
+// Used to overflow in `is_normalizable`
+
+use std::marker::PhantomData;
+
+struct Node<T: 'static> {
+    m: PhantomData<&'static T>,
+}
+
+struct Digit<T> {
+    elem: T,
+}
+
+enum FingerTree<T: 'static> {
+    Single(T),
+
+    Deep(Digit<T>, Box<FingerTree<Node<T>>>),
+}
+
+fn main() {}

tests/ui/large_enum_variant.64bit.stderr

@@ -276,5 +276,21 @@ help: consider boxing the large fields to reduce the total size of the enum
 LL |     Error(Box<PossiblyLargeEnumWithConst<256>>),
    |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-error: aborting due to 16 previous errors
+error: large size difference between variants
+  --> tests/ui/large_enum_variant.rs:167:1
+   |
+LL | / enum SelfRef<'a> {
+LL | |     Small,
+   | |     ----- the second-largest variant carries no data at all
+LL | |     Large([&'a SelfRef<'a>; 1024]),
+   | |     ------------------------------ the largest variant contains at least 8192 bytes
+LL | | }
+   | |_^ the entire enum is at least 8192 bytes
+   |
+help: consider boxing the large fields to reduce the total size of the enum
+   |
+LL |     Large(Box<[&'a SelfRef<'a>; 1024]>),
+   |           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 17 previous errors
 

tests/ui/large_enum_variant.rs

@@ -163,3 +163,8 @@ fn main() {
         }
     );
 }
+
+enum SelfRef<'a> {
+    Small,
+    Large([&'a SelfRef<'a>; 1024]),
+}