89 lines
3.4 KiB
Rust
89 lines
3.4 KiB
Rust
use crate::{context::LintContext, LateContext, LateLintPass};
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use rustc_errors::fluent;
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use rustc_hir as hir;
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use rustc_middle::ty::{visit::TypeVisitable, Ty};
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use rustc_span::{symbol::sym, Span};
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declare_lint! {
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/// The `enum_intrinsics_non_enums` lint detects calls to
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/// intrinsic functions that require an enum ([`core::mem::discriminant`],
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/// [`core::mem::variant_count`]), but are called with a non-enum type.
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///
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/// [`core::mem::discriminant`]: https://doc.rust-lang.org/core/mem/fn.discriminant.html
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/// [`core::mem::variant_count`]: https://doc.rust-lang.org/core/mem/fn.variant_count.html
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///
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/// ### Example
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///
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/// ```rust,compile_fail
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/// #![deny(enum_intrinsics_non_enums)]
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/// core::mem::discriminant::<i32>(&123);
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/// ```
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///
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/// {{produces}}
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///
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/// ### Explanation
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///
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/// In order to accept any enum, the `mem::discriminant` and
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/// `mem::variant_count` functions are generic over a type `T`.
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/// This makes it technically possible for `T` to be a non-enum,
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/// in which case the return value is unspecified.
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///
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/// This lint prevents such incorrect usage of these functions.
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ENUM_INTRINSICS_NON_ENUMS,
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Deny,
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"detects calls to `core::mem::discriminant` and `core::mem::variant_count` with non-enum types"
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}
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declare_lint_pass!(EnumIntrinsicsNonEnums => [ENUM_INTRINSICS_NON_ENUMS]);
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/// Returns `true` if we know for sure that the given type is not an enum. Note that for cases where
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/// the type is generic, we can't be certain if it will be an enum so we have to assume that it is.
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fn is_non_enum(t: Ty<'_>) -> bool {
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!t.is_enum() && !t.needs_subst()
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}
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fn enforce_mem_discriminant(
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cx: &LateContext<'_>,
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func_expr: &hir::Expr<'_>,
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expr_span: Span,
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args_span: Span,
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) {
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let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
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if is_non_enum(ty_param) {
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cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, expr_span, |builder| {
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builder
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.build(fluent::lint::enum_intrinsics_mem_discriminant)
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.set_arg("ty_param", ty_param)
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.span_note(args_span, fluent::lint::note)
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.emit();
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});
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}
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}
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fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, span: Span) {
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let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
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if is_non_enum(ty_param) {
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cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, span, |builder| {
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builder
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.build(fluent::lint::enum_intrinsics_mem_variant)
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.set_arg("ty_param", ty_param)
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.note(fluent::lint::note)
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.emit();
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});
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}
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}
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impl<'tcx> LateLintPass<'tcx> for EnumIntrinsicsNonEnums {
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fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
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let hir::ExprKind::Call(func, args) = &expr.kind else { return };
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let hir::ExprKind::Path(qpath) = &func.kind else { return };
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let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() else { return };
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let Some(name) = cx.tcx.get_diagnostic_name(def_id) else { return };
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match name {
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sym::mem_discriminant => enforce_mem_discriminant(cx, func, expr.span, args[0].span),
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sym::mem_variant_count => enforce_mem_variant_count(cx, func, expr.span),
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_ => {}
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}
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}
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}
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