3 lints::{EnumIntrinsicsMemDiscriminate, EnumIntrinsicsMemVariant},
4 LateContext, LateLintPass,
7 use rustc_middle::ty::{visit::TypeVisitable, Ty};
8 use rustc_span::{symbol::sym, Span};
11 /// The `enum_intrinsics_non_enums` lint detects calls to
12 /// intrinsic functions that require an enum ([`core::mem::discriminant`],
13 /// [`core::mem::variant_count`]), but are called with a non-enum type.
15 /// [`core::mem::discriminant`]: https://doc.rust-lang.org/core/mem/fn.discriminant.html
16 /// [`core::mem::variant_count`]: https://doc.rust-lang.org/core/mem/fn.variant_count.html
20 /// ```rust,compile_fail
21 /// #![deny(enum_intrinsics_non_enums)]
22 /// core::mem::discriminant::<i32>(&123);
29 /// In order to accept any enum, the `mem::discriminant` and
30 /// `mem::variant_count` functions are generic over a type `T`.
31 /// This makes it technically possible for `T` to be a non-enum,
32 /// in which case the return value is unspecified.
34 /// This lint prevents such incorrect usage of these functions.
35 ENUM_INTRINSICS_NON_ENUMS,
37 "detects calls to `core::mem::discriminant` and `core::mem::variant_count` with non-enum types"
40 declare_lint_pass!(EnumIntrinsicsNonEnums => [ENUM_INTRINSICS_NON_ENUMS]);
42 /// Returns `true` if we know for sure that the given type is not an enum. Note that for cases where
43 /// the type is generic, we can't be certain if it will be an enum so we have to assume that it is.
44 fn is_non_enum(t: Ty<'_>) -> bool {
45 !t.is_enum() && !t.needs_subst()
48 fn enforce_mem_discriminant(
50 func_expr: &hir::Expr<'_>,
54 let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
55 if is_non_enum(ty_param) {
57 ENUM_INTRINSICS_NON_ENUMS,
59 EnumIntrinsicsMemDiscriminate { ty_param, note: args_span },
64 fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, span: Span) {
65 let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
66 if is_non_enum(ty_param) {
68 ENUM_INTRINSICS_NON_ENUMS,
70 EnumIntrinsicsMemVariant { ty_param },
75 impl<'tcx> LateLintPass<'tcx> for EnumIntrinsicsNonEnums {
76 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
77 let hir::ExprKind::Call(func, args) = &expr.kind else { return };
78 let hir::ExprKind::Path(qpath) = &func.kind else { return };
79 let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() else { return };
80 let Some(name) = cx.tcx.get_diagnostic_name(def_id) else { return };
82 sym::mem_discriminant => enforce_mem_discriminant(cx, func, expr.span, args[0].span),
83 sym::mem_variant_count => enforce_mem_variant_count(cx, func, expr.span),