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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::{ast_utils, is_direct_expn_of};
use rustc_ast::ast::{Expr, ExprKind, Lit, LitKind};
use rustc_errors::Applicability;
use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
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.
///
/// **Known problems:** None.
///
/// **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 {
kind: LitKind::Bool(_),
..
})
) && !e.span.from_expansion()
}
impl EarlyLintPass for BoolAssertComparison {
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &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(e.span, mac) {
if let Some([a, b]) = ast_utils::extract_assert_macro_args(e) {
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;
}
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;
}
}
}
}
}
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