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use clippy_utils::{diagnostics::span_lint_and_sugg, higher, is_direct_expn_of, ty::implements_trait};
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::*;
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
/// // Bad
/// assert_eq!("a".is_empty(), false);
/// assert_ne!("a".is_empty(), true);
///
/// // Good
/// assert!(!"a".is_empty());
/// ```
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 impl_not_trait_with_bool_out(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
let ty = cx.typeck_results().expr_ty(e);
cx.tcx
.lang_items()
.not_trait()
.filter(|id| implements_trait(cx, ty, *id, &[]))
.and_then(|id| {
cx.tcx.associated_items(id).find_by_name_and_kind(
cx.tcx,
Ident::from_str("Output"),
ty::AssocKind::Type,
id,
)
})
.map_or(false, |item| {
let proj = cx.tcx.mk_projection(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 macros = ["assert_eq", "debug_assert_eq"];
let inverted_macros = ["assert_ne", "debug_assert_ne"];
for mac in macros.iter().chain(inverted_macros.iter()) {
if let Some(span) = is_direct_expn_of(expr.span, mac) {
if let Some(args) = higher::extract_assert_macro_args(expr) {
if let [a, b, ..] = args[..] {
let nb_bool_args = is_bool_lit(a) as usize + is_bool_lit(b) as usize;
if nb_bool_args != 1 {
// 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 !impl_not_trait_with_bool_out(cx, a) || !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 non_eq_mac = &mac[..mac.len() - 3];
span_lint_and_sugg(
cx,
BOOL_ASSERT_COMPARISON,
span,
&format!("used `{}!` with a literal bool", mac),
"replace it with",
format!("{}!(..)", non_eq_mac),
Applicability::MaybeIncorrect,
);
return;
}
}
}
}
}
}
|
