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use crate::{context::LintContext, LateContext, LateLintPass};
use rustc_errors::fluent;
use rustc_hir as hir;
use rustc_middle::ty::{visit::TypeVisitable, Ty};
use rustc_span::{symbol::sym, Span};
declare_lint! {
ENUM_INTRINSICS_NON_ENUMS,
Deny,
"detects calls to `core::mem::discriminant` and `core::mem::variant_count` with non-enum types"
}
declare_lint_pass!(EnumIntrinsicsNonEnums => [ENUM_INTRINSICS_NON_ENUMS]);
fn is_non_enum(t: Ty<'_>) -> bool {
!t.is_enum() && !t.needs_subst()
}
fn enforce_mem_discriminant(
cx: &LateContext<'_>,
func_expr: &hir::Expr<'_>,
expr_span: Span,
args_span: Span,
) {
let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
if is_non_enum(ty_param) {
cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, expr_span, |builder| {
builder
.build(fluent::lint::enum_intrinsics_mem_discriminant)
.set_arg("ty_param", ty_param)
.span_note(args_span, fluent::lint::note)
.emit();
});
}
}
fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, span: Span) {
let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
if is_non_enum(ty_param) {
cx.struct_span_lint(ENUM_INTRINSICS_NON_ENUMS, span, |builder| {
builder
.build(fluent::lint::enum_intrinsics_mem_variant)
.set_arg("ty_param", ty_param)
.note(fluent::lint::note)
.emit();
});
}
}
impl<'tcx> LateLintPass<'tcx> for EnumIntrinsicsNonEnums {
fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
let hir::ExprKind::Call(func, args) = &expr.kind else { return };
let hir::ExprKind::Path(qpath) = &func.kind else { return };
let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() else { return };
let Some(name) = cx.tcx.get_diagnostic_name(def_id) else { return };
match name {
sym::mem_discriminant => enforce_mem_discriminant(cx, func, expr.span, args[0].span),
sym::mem_variant_count => enforce_mem_variant_count(cx, func, expr.span),
_ => {}
}
}
}