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use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::macros::{find_assert_eq_args, root_macro_call_first_node};
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::{implements_trait, is_copy};
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, Lit};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::ty::{self, 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 extract_bool_lit(e: &Expr<'_>) -> Option<bool> {
if let ExprKind::Lit(Lit {
node: LitKind::Bool(b), ..
}) = e.kind
&& !e.span.from_expansion()
{
Some(b)
} else {
None
}
}
fn is_impl_not_trait_with_bool_out<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
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);
let eq_macro = match macro_name.as_str() {
"assert_eq" | "debug_assert_eq" => true,
"assert_ne" | "debug_assert_ne" => false,
_ => return,
};
let Some ((a, b, _)) = find_assert_eq_args(cx, expr, macro_call.expn) else { return };
let a_span = a.span.source_callsite();
let b_span = b.span.source_callsite();
let (lit_span, bool_value, non_lit_expr) = match (extract_bool_lit(a), extract_bool_lit(b)) {
// assert_eq!(true/false, b)
// ^^^^^^^^^^^^
(Some(bool_value), None) => (a_span.until(b_span), bool_value, b),
// assert_eq!(a, true/false)
// ^^^^^^^^^^^^
(None, Some(bool_value)) => (b_span.with_lo(a_span.hi()), bool_value, a),
// 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,
};
let non_lit_ty = cx.typeck_results().expr_ty(non_lit_expr);
if !is_impl_not_trait_with_bool_out(cx, non_lit_ty) {
// 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;
}
if !is_copy(cx, non_lit_ty) {
// Only lint with types that are `Copy` because `assert!(x)` takes
// ownership of `x` whereas `assert_eq(x, true)` does not
return;
}
let macro_name = macro_name.as_str();
let non_eq_mac = ¯o_name[..macro_name.len() - 3];
span_lint_and_then(
cx,
BOOL_ASSERT_COMPARISON,
macro_call.span,
&format!("used `{macro_name}!` with a literal bool"),
|diag| {
// assert_eq!(...)
// ^^^^^^^^^
let name_span = cx.sess().source_map().span_until_char(macro_call.span, '!');
let mut suggestions = vec![(name_span, non_eq_mac.to_string()), (lit_span, String::new())];
if bool_value ^ eq_macro {
let Some(sugg) = Sugg::hir_opt(cx, non_lit_expr) else { return };
suggestions.push((non_lit_expr.span, (!sugg).to_string()));
}
diag.multipart_suggestion(
format!("replace it with `{non_eq_mac}!(..)`"),
suggestions,
Applicability::MachineApplicable,
);
},
);
}
}
|
