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use clippy_utils::macros::{find_assert_eq_args, root_macro_call_first_node};
use clippy_utils::{diagnostics::span_lint_and_sugg, ty::implements_trait};
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, Lit};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::Ident;
declare_clippy_lint! {
/// ### What it does
/// This lint warns about boolean comparisons in assert-like macros.
///
/// ### Why is this bad?
/// It is shorter to use the equivalent.
///
/// ### Example
/// ```rust
/// assert_eq!("a".is_empty(), false);
/// assert_ne!("a".is_empty(), true);
/// ```
///
/// Use instead:
/// ```rust
/// assert!(!"a".is_empty());
/// ```
#[clippy::version = "1.53.0"]
pub BOOL_ASSERT_COMPARISON,
style,
"Using a boolean as comparison value in an assert_* macro when there is no need"
}
declare_lint_pass!(BoolAssertComparison => [BOOL_ASSERT_COMPARISON]);
fn is_bool_lit(e: &Expr<'_>) -> bool {
matches!(
e.kind,
ExprKind::Lit(Lit {
node: LitKind::Bool(_),
..
})
) && !e.span.from_expansion()
}
fn is_impl_not_trait_with_bool_out(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
let ty = cx.typeck_results().expr_ty(e);
cx.tcx
.lang_items()
.not_trait()
.filter(|trait_id| implements_trait(cx, ty, *trait_id, &[]))
.and_then(|trait_id| {
cx.tcx.associated_items(trait_id).find_by_name_and_kind(
cx.tcx,
Ident::from_str("Output"),
ty::AssocKind::Type,
trait_id,
)
})
.map_or(false, |assoc_item| {
let proj = cx.tcx.mk_projection(assoc_item.def_id, cx.tcx.mk_substs_trait(ty, []));
let nty = cx.tcx.normalize_erasing_regions(cx.param_env, proj);
nty.is_bool()
})
}
impl<'tcx> LateLintPass<'tcx> for BoolAssertComparison {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let Some(macro_call) = root_macro_call_first_node(cx, expr) else { return };
let macro_name = cx.tcx.item_name(macro_call.def_id);
if !matches!(
macro_name.as_str(),
"assert_eq" | "debug_assert_eq" | "assert_ne" | "debug_assert_ne"
) {
return;
}
let Some ((a, b, _)) = find_assert_eq_args(cx, expr, macro_call.expn) else { return };
if !(is_bool_lit(a) ^ is_bool_lit(b)) {
// If there are two boolean arguments, we definitely don't understand
// what's going on, so better leave things as is...
//
// Or there is simply no boolean and then we can leave things as is!
return;
}
if !is_impl_not_trait_with_bool_out(cx, a) || !is_impl_not_trait_with_bool_out(cx, b) {
// At this point the expression which is not a boolean
// literal does not implement Not trait with a bool output,
// so we cannot suggest to rewrite our code
return;
}
let macro_name = macro_name.as_str();
let non_eq_mac = ¯o_name[..macro_name.len() - 3];
span_lint_and_sugg(
cx,
BOOL_ASSERT_COMPARISON,
macro_call.span,
&format!("used `{macro_name}!` with a literal bool"),
"replace it with",
format!("{non_eq_mac}!(..)"),
Applicability::MaybeIncorrect,
);
}
}
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