1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::get_parent_expr;
3 use clippy_utils::numeric_literal::NumericLiteral;
4 use clippy_utils::source::snippet_opt;
5 use if_chain::if_chain;
6 use rustc_ast::{LitFloatType, LitIntType, LitKind};
7 use rustc_errors::Applicability;
8 use rustc_hir::def::Res;
9 use rustc_hir::{Expr, ExprKind, Lit, QPath, TyKind, UnOp};
10 use rustc_lint::{LateContext, LintContext};
11 use rustc_middle::lint::in_external_macro;
12 use rustc_middle::ty::{self, FloatTy, InferTy, Ty};
14 use super::UNNECESSARY_CAST;
16 pub(super) fn check<'tcx>(
17 cx: &LateContext<'tcx>,
19 cast_expr: &Expr<'tcx>,
23 // skip non-primitive type cast
25 if let ExprKind::Cast(_, cast_to) = expr.kind;
26 if let TyKind::Path(QPath::Resolved(_, path)) = &cast_to.kind;
27 if let Res::PrimTy(_) = path.res;
34 let cast_str = snippet_opt(cx, cast_expr.span).unwrap_or_default();
36 if let Some(lit) = get_numeric_literal(cast_expr) {
37 let literal_str = &cast_str;
40 if let LitKind::Int(n, _) = lit.node;
41 if let Some(src) = snippet_opt(cx, cast_expr.span);
42 if cast_to.is_floating_point();
43 if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node);
44 let from_nbits = 128 - n.leading_zeros();
45 let to_nbits = fp_ty_mantissa_nbits(cast_to);
46 if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits && num_lit.is_decimal();
48 lint_unnecessary_cast(cx, expr, num_lit.integer, cast_from, cast_to);
54 LitKind::Int(_, LitIntType::Unsuffixed) if cast_to.is_integral() => {
55 lint_unnecessary_cast(cx, expr, literal_str, cast_from, cast_to);
58 LitKind::Float(_, LitFloatType::Unsuffixed) if cast_to.is_floating_point() => {
59 lint_unnecessary_cast(cx, expr, literal_str, cast_from, cast_to);
62 LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {
65 LitKind::Int(_, LitIntType::Signed(_) | LitIntType::Unsigned(_))
66 | LitKind::Float(_, LitFloatType::Suffixed(_))
67 if cast_from.kind() == cast_to.kind() =>
69 if let Some(src) = snippet_opt(cx, cast_expr.span) {
70 if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node) {
71 lint_unnecessary_cast(cx, expr, num_lit.integer, cast_from, cast_to);
80 if cast_from.kind() == cast_to.kind() && !in_external_macro(cx.sess(), expr.span) {
85 &format!("casting to the same type is unnecessary (`{cast_from}` -> `{cast_to}`)"),
88 Applicability::MachineApplicable,
96 fn lint_unnecessary_cast(
99 raw_literal_str: &str,
103 let literal_kind_name = if cast_from.is_integral() { "integer" } else { "float" };
104 // first we remove all matches so `-(1)` become `-1`, and remove trailing dots, so `1.` become `1`
105 let literal_str = raw_literal_str
106 .replace(['(', ')'], "")
107 .trim_end_matches('.')
109 // we know need to check if the parent is a method call, to add parenthesis accordingly (eg:
110 // (-1).foo() instead of -1.foo())
111 let sugg = if let Some(parent_expr) = get_parent_expr(cx, expr)
112 && let ExprKind::MethodCall(..) = parent_expr.kind
113 && literal_str.starts_with('-')
115 format!("({literal_str}_{cast_to})")
118 format!("{literal_str}_{cast_to}")
125 &format!("casting {literal_kind_name} literal to `{cast_to}` is unnecessary"),
128 Applicability::MachineApplicable,
132 fn get_numeric_literal<'e>(expr: &'e Expr<'e>) -> Option<&'e Lit> {
134 ExprKind::Lit(ref lit) => Some(lit),
135 ExprKind::Unary(UnOp::Neg, e) => {
136 if let ExprKind::Lit(ref lit) = e.kind {
146 /// Returns the mantissa bits wide of a fp type.
147 /// Will return 0 if the type is not a fp
148 fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
150 ty::Float(FloatTy::F32) => 23,
151 ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,