1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use rustc_ast::ast::{Expr, ExprKind, LitFloatType, LitKind};
3 use rustc_errors::Applicability;
4 use rustc_lint::{EarlyContext, EarlyLintPass};
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 /// Detects cases where a whole-number literal float is being rounded, using
11 /// the `floor`, `ceil`, or `round` methods.
13 /// ### Why is this bad?
15 /// This is unnecessary and confusing to the reader. Doing this is probably a mistake.
19 /// let x = 1f32.ceil();
25 #[clippy::version = "1.62.0"]
28 "Uselessly rounding a whole number floating-point literal"
30 declare_lint_pass!(UnusedRounding => [UNUSED_ROUNDING]);
32 fn is_useless_rounding(expr: &Expr) -> Option<(&str, String)> {
33 if let ExprKind::MethodCall(name_ident, receiver, _, _) = &expr.kind
34 && let method_name = name_ident.ident.name.as_str()
35 && (method_name == "ceil" || method_name == "round" || method_name == "floor")
36 && let ExprKind::Lit(spanned) = &receiver.kind
37 && let LitKind::Float(symbol, ty) = spanned.kind {
38 let f = symbol.as_str().parse::<f64>().unwrap();
39 let f_str = symbol.to_string() + if let LitFloatType::Suffixed(ty) = ty {
45 Some((method_name, f_str))
54 impl EarlyLintPass for UnusedRounding {
55 fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
56 if let Some((method_name, float)) = is_useless_rounding(expr) {
61 &format!("used the `{}` method with a whole number float", method_name),
62 &format!("remove the `{}` method call", method_name),
64 Applicability::MachineApplicable,