| use clippy_utils::diagnostics::span_lint_and_sugg; |
| use clippy_utils::source::snippet; |
| use rustc_ast::ast::{Expr, ExprKind, MethodCall}; |
| use rustc_errors::Applicability; |
| use rustc_lint::{EarlyContext, EarlyLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| |
| declare_clippy_lint! { |
| /// ### What it does |
| /// |
| /// Detects cases where a whole-number literal float is being rounded, using |
| /// the `floor`, `ceil`, or `round` methods. |
| /// |
| /// ### Why is this bad? |
| /// |
| /// This is unnecessary and confusing to the reader. Doing this is probably a mistake. |
| /// |
| /// ### Example |
| /// ```no_run |
| /// let x = 1f32.ceil(); |
| /// ``` |
| /// Use instead: |
| /// ```no_run |
| /// let x = 1f32; |
| /// ``` |
| #[clippy::version = "1.63.0"] |
| pub UNUSED_ROUNDING, |
| nursery, |
| "Uselessly rounding a whole number floating-point literal" |
| } |
| declare_lint_pass!(UnusedRounding => [UNUSED_ROUNDING]); |
| |
| fn is_useless_rounding<'a>(cx: &EarlyContext<'_>, expr: &'a Expr) -> Option<(&'a str, String)> { |
| if let ExprKind::MethodCall(box MethodCall { |
| seg: name_ident, |
| receiver, |
| .. |
| }) = &expr.kind |
| && let method_name = name_ident.ident.name.as_str() |
| && (method_name == "ceil" || method_name == "round" || method_name == "floor") |
| && let ExprKind::Lit(token_lit) = &receiver.kind |
| && token_lit.is_semantic_float() |
| && let Ok(f) = token_lit.symbol.as_str().replace('_', "").parse::<f64>() |
| { |
| (f.fract() == 0.0).then(|| (method_name, snippet(cx, receiver.span, "..").to_string())) |
| } else { |
| None |
| } |
| } |
| |
| impl EarlyLintPass for UnusedRounding { |
| fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) { |
| if let Some((method_name, float)) = is_useless_rounding(cx, expr) { |
| span_lint_and_sugg( |
| cx, |
| UNUSED_ROUNDING, |
| expr.span, |
| &format!("used the `{method_name}` method with a whole number float"), |
| &format!("remove the `{method_name}` method call"), |
| float, |
| Applicability::MachineApplicable, |
| ); |
| } |
| } |
| } |