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