Make Clippy understand generic const items

Author: fmease

src/tools/clippy/clippy_lints/src/large_const_arrays.rs

@@ -50,7 +50,11 @@ impl<'tcx> LateLintPass<'tcx> for LargeConstArrays {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
         if_chain! {
             if !item.span.from_expansion();
-            if let ItemKind::Const(hir_ty, _) = &item.kind;
+            if let ItemKind::Const(hir_ty, generics, _) = &item.kind;
+            // Since static items may not have generics, skip generic const items.
+            // FIXME(generic_const_items): I don't think checking `generics.hwcp` suffices as it
+            // doesn't account for empty where-clauses that only consist of keyword `where` IINM.
+            if generics.params.is_empty() && !generics.has_where_clause_predicates;
             let ty = hir_ty_to_ty(cx.tcx, hir_ty);
             if let ty::Array(element_type, cst) = ty.kind();
             if let ConstKind::Value(ty::ValTree::Leaf(element_count)) = cst.kind();

src/tools/clippy/clippy_lints/src/non_copy_const.rs

@@ -302,7 +302,7 @@ declare_lint_pass!(NonCopyConst => [DECLARE_INTERIOR_MUTABLE_CONST, BORROW_INTER
 
 impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
     fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx Item<'_>) {
-        if let ItemKind::Const(hir_ty, body_id) = it.kind {
+        if let ItemKind::Const(hir_ty, _generics, body_id) = it.kind {
             let ty = hir_ty_to_ty(cx.tcx, hir_ty);
             if !ignored_macro(cx, it) && is_unfrozen(cx, ty) && is_value_unfrozen_poly(cx, body_id, ty) {
                 lint(cx, Source::Item { item: it.span });

src/tools/clippy/clippy_lints/src/types/mod.rs

@@ -349,7 +349,7 @@ impl<'tcx> LateLintPass<'tcx> for Types {
         let is_exported = cx.effective_visibilities.is_exported(item.owner_id.def_id);
 
         match item.kind {
-            ItemKind::Static(ty, _, _) | ItemKind::Const(ty, _) => self.check_ty(
+            ItemKind::Static(ty, _, _) | ItemKind::Const(ty, _, _) => self.check_ty(
                 cx,
                 ty,
                 CheckTyContext {

src/tools/clippy/clippy_utils/src/ast_utils.rs

@@ -301,15 +301,17 @@ pub fn eq_item_kind(l: &ItemKind, r: &ItemKind) -> bool {
         (
             Const(box ast::ConstItem {
                 defaultness: ld,
+                generics: lg,
                 ty: lt,
                 expr: le,
             }),
             Const(box ast::ConstItem {
                 defaultness: rd,
+                generics: rg,
                 ty: rt,
                 expr: re,
             }),
-        ) => eq_defaultness(*ld, *rd) && eq_ty(lt, rt) && eq_expr_opt(le, re),
+        ) => eq_defaultness(*ld, *rd) && eq_generics(lg, rg) && eq_ty(lt, rt) && eq_expr_opt(le, re),
         (
             Fn(box ast::Fn {
                 defaultness: ld,
@@ -476,15 +478,17 @@ pub fn eq_assoc_item_kind(l: &AssocItemKind, r: &AssocItemKind) -> bool {
         (
             Const(box ast::ConstItem {
                 defaultness: ld,
+                generics: lg,
                 ty: lt,
                 expr: le,
             }),
             Const(box ast::ConstItem {
                 defaultness: rd,
+                generics: rg,
                 ty: rt,
                 expr: re,
             }),
-        ) => eq_defaultness(*ld, *rd) && eq_ty(lt, rt) && eq_expr_opt(le, re),
+        ) => eq_defaultness(*ld, *rd) && eq_generics(lg, rg) && eq_ty(lt, rt) && eq_expr_opt(le, re),
         (
             Fn(box ast::Fn {
                 defaultness: ld,

src/tools/clippy/clippy_utils/src/consts.rs

@@ -461,7 +461,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                 // Check if this constant is based on `cfg!(..)`,
                 // which is NOT constant for our purposes.
                 if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id)
-                    && let Node::Item(Item { kind: ItemKind::Const(_, body_id), .. }) = node
+                    && let Node::Item(Item { kind: ItemKind::Const(.., body_id), .. }) = node
                     && let Node::Expr(Expr { kind: ExprKind::Lit(_), span, .. }) = self.lcx
                         .tcx
                         .hir()

src/tools/clippy/clippy_utils/src/lib.rs

@@ -2380,7 +2380,7 @@ fn with_test_item_names(tcx: TyCtxt<'_>, module: LocalDefId, f: impl Fn(&[Symbol
             for id in tcx.hir().module_items(module) {
                 if matches!(tcx.def_kind(id.owner_id), DefKind::Const)
                     && let item = tcx.hir().item(id)
-                    && let ItemKind::Const(ty, _body) = item.kind {
+                    && let ItemKind::Const(ty, _generics, _body) = item.kind {
                     if let TyKind::Path(QPath::Resolved(_, path)) = ty.kind {
                         // We could also check for the type name `test::TestDescAndFn`
                         if let Res::Def(DefKind::Struct, _) = path.res {