Use ConstArg for array lengths

clippy_lints/src/large_stack_arrays.rs

@@ -106,13 +106,12 @@ fn might_be_expanded<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> bool {
     ///
     /// This is a fail-safe to a case where even the `is_from_proc_macro` is unable to determain the
     /// correct result.
-    fn repeat_expr_might_be_expanded<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> bool {
-        let ExprKind::Repeat(_, ArrayLen::Body(anon_const)) = expr.kind else {
+    fn repeat_expr_might_be_expanded<'tcx>(expr: &Expr<'tcx>) -> bool {
+        let ExprKind::Repeat(_, ArrayLen::Body(len_ct)) = expr.kind else {
             return false;
         };
-        let len_span = cx.tcx.def_span(anon_const.def_id);
-        !expr.span.contains(len_span)
+        !expr.span.contains(len_ct.span())
     }
 
-    expr.span.from_expansion() || is_from_proc_macro(cx, expr) || repeat_expr_might_be_expanded(cx, expr)
+    expr.span.from_expansion() || is_from_proc_macro(cx, expr) || repeat_expr_might_be_expanded(expr)
 }

clippy_lints/src/trailing_empty_array.rs

@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::span_lint_and_help;
 use clippy_utils::has_repr_attr;
 use rustc_hir::{Item, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::Const;
+use rustc_middle::ty::{Const, FeedConstTy};
 use rustc_session::declare_lint_pass;
 
 declare_clippy_lint! {
@@ -53,14 +53,14 @@ impl<'tcx> LateLintPass<'tcx> for TrailingEmptyArray {
     }
 }
 
-fn is_struct_with_trailing_zero_sized_array(cx: &LateContext<'_>, item: &Item<'_>) -> bool {
+fn is_struct_with_trailing_zero_sized_array<'tcx>(cx: &LateContext<'tcx>, item: &Item<'tcx>) -> bool {
     if let ItemKind::Struct(data, _) = &item.kind
         // First check if last field is an array
         && let Some(last_field) = data.fields().last()
         && let rustc_hir::TyKind::Array(_, rustc_hir::ArrayLen::Body(length)) = last_field.ty.kind
 
         // Then check if that array is zero-sized
-        && let length = Const::from_anon_const(cx.tcx, length.def_id)
+        && let length = Const::from_const_arg(cx.tcx, length, FeedConstTy::No)
         && let length = length.try_eval_target_usize(cx.tcx, cx.param_env)
         && let Some(length) = length
     {

clippy_lints/src/utils/author.rs

@@ -5,10 +5,9 @@ use clippy_utils::{get_attr, higher};
 use rustc_ast::ast::{LitFloatType, LitKind};
 use rustc_ast::LitIntType;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_hir as hir;
 use rustc_hir::{
-    ArrayLen, BindingMode, CaptureBy, Closure, ClosureKind, CoroutineKind, ExprKind, FnRetTy, HirId, Lit, PatKind,
-    QPath, StmtKind, TyKind,
+    self as hir, ArrayLen, BindingMode, CaptureBy, Closure, ClosureKind, ConstArg, ConstArgKind, CoroutineKind,
+    ExprKind, FnRetTy, HirId, Lit, PatKind, QPath, StmtKind, TyKind,
 };
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_session::declare_lint_pass;
@@ -270,6 +269,22 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
         }
     }
 
+    fn const_arg(&self, const_arg: &Binding<&ConstArg<'_>>) {
+        match const_arg.value.kind {
+            // FIXME: uncomment for ConstArgKind::Path
+            // ConstArgKind::Path(ref qpath) => {
+            //     bind!(self, qpath);
+            //     chain!(self, "let ConstArgKind::Path(ref {qpath}) = {const_arg}.kind");
+            //     self.qpath(qpath);
+            // },
+            ConstArgKind::Anon(anon_const) => {
+                bind!(self, anon_const);
+                chain!(self, "let ConstArgKind::({anon_const}) = {const_arg}.kind");
+                self.body(field!(anon_const.body));
+            },
+        }
+    }
+
     fn lit(&self, lit: &Binding<&Lit>) {
         let kind = |kind| chain!(self, "let LitKind::{kind} = {lit}.node");
         macro_rules! kind {
@@ -602,10 +617,10 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
                 self.expr(value);
                 match length.value {
                     ArrayLen::Infer(..) => chain!(self, "let ArrayLen::Infer(..) = length"),
-                    ArrayLen::Body(anon_const) => {
-                        bind!(self, anon_const);
-                        chain!(self, "let ArrayLen::Body({anon_const}) = {length}");
-                        self.body(field!(anon_const.body));
+                    ArrayLen::Body(const_arg) => {
+                        bind!(self, const_arg);
+                        chain!(self, "let ArrayLen::Body({const_arg}) = {length}");
+                        self.const_arg(const_arg);
                     },
                 }
             },

clippy_utils/src/hir_utils.rs

@@ -227,7 +227,7 @@ impl HirEqInterExpr<'_, '_, '_> {
     pub fn eq_array_length(&mut self, left: ArrayLen<'_>, right: ArrayLen<'_>) -> bool {
         match (left, right) {
             (ArrayLen::Infer(..), ArrayLen::Infer(..)) => true,
-            (ArrayLen::Body(l_ct), ArrayLen::Body(r_ct)) => self.eq_body(l_ct.body, r_ct.body),
+            (ArrayLen::Body(l_ct), ArrayLen::Body(r_ct)) => self.eq_const_arg(l_ct, r_ct),
             (_, _) => false,
         }
     }
@@ -1129,7 +1129,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
     pub fn hash_array_length(&mut self, length: ArrayLen<'_>) {
         match length {
             ArrayLen::Infer(..) => {},
-            ArrayLen::Body(anon_const) => self.hash_body(anon_const.body),
+            ArrayLen::Body(ct) => self.hash_const_arg(ct),
         }
     }
 

clippy_utils/src/lib.rs

@@ -102,11 +102,11 @@ use rustc_hir::hir_id::{HirIdMap, HirIdSet};
 use rustc_hir::intravisit::{walk_expr, FnKind, Visitor};
 use rustc_hir::LangItem::{OptionNone, OptionSome, ResultErr, ResultOk};
 use rustc_hir::{
-    self as hir, def, Arm, ArrayLen, BindingMode, Block, BlockCheckMode, Body, ByRef, Closure, ConstContext,
-    Destination, Expr, ExprField, ExprKind, FnDecl, FnRetTy, GenericArgs, HirId, Impl, ImplItem, ImplItemKind,
-    ImplItemRef, Item, ItemKind, LangItem, LetStmt, MatchSource, Mutability, Node, OwnerId, OwnerNode, Param, Pat,
-    PatKind, Path, PathSegment, PrimTy, QPath, Stmt, StmtKind, TraitItem, TraitItemKind, TraitItemRef, TraitRef,
-    TyKind, UnOp,
+    self as hir, def, Arm, ArrayLen, BindingMode, Block, BlockCheckMode, Body, ByRef, Closure, ConstArgKind,
+    ConstContext, Destination, Expr, ExprField, ExprKind, FnDecl, FnRetTy, GenericArgs, HirId, Impl, ImplItem,
+    ImplItemKind, ImplItemRef, Item, ItemKind, LangItem, LetStmt, MatchSource, Mutability, Node, OwnerId, OwnerNode,
+    Param, Pat, PatKind, Path, PathSegment, PrimTy, QPath, Stmt, StmtKind, TraitItem, TraitItemKind, TraitItemRef,
+    TraitRef, TyKind, UnOp,
 };
 use rustc_lexer::{tokenize, TokenKind};
 use rustc_lint::{LateContext, Level, Lint, LintContext};
@@ -904,7 +904,9 @@ pub fn is_default_equivalent(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
         },
         ExprKind::Tup(items) | ExprKind::Array(items) => items.iter().all(|x| is_default_equivalent(cx, x)),
         ExprKind::Repeat(x, ArrayLen::Body(len)) => {
-            if let ExprKind::Lit(const_lit) = cx.tcx.hir().body(len.body).value.kind
+            #[allow(irrefutable_let_patterns)] // FIXME
+            if let ConstArgKind::Anon(anon_const) = len.kind
+                && let ExprKind::Lit(const_lit) = cx.tcx.hir().body(anon_const.body).value.kind
                 && let LitKind::Int(v, _) = const_lit.node
                 && v <= 32
                 && is_default_equivalent(cx, x)
@@ -933,7 +935,9 @@ fn is_default_equivalent_from(cx: &LateContext<'_>, from_func: &Expr<'_>, arg: &
             }) => return sym.is_empty() && is_path_lang_item(cx, ty, LangItem::String),
             ExprKind::Array([]) => return is_path_diagnostic_item(cx, ty, sym::Vec),
             ExprKind::Repeat(_, ArrayLen::Body(len)) => {
-                if let ExprKind::Lit(const_lit) = cx.tcx.hir().body(len.body).value.kind
+                #[allow(irrefutable_let_patterns)] // FIXME
+                if let ConstArgKind::Anon(anon_const) = len.kind
+                    && let ExprKind::Lit(const_lit) = cx.tcx.hir().body(anon_const.body).value.kind
                     && let LitKind::Int(v, _) = const_lit.node
                 {
                     return v == 0 && is_path_diagnostic_item(cx, ty, sym::Vec);