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|
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::numeric_literal::NumericLiteral;
use clippy_utils::source::snippet_opt;
use if_chain::if_chain;
use rustc_ast::{LitFloatType, LitIntType, LitKind};
use rustc_errors::Applicability;
use rustc_hir::def::Res;
use rustc_hir::{Expr, ExprKind, Lit, QPath, TyKind, UnOp};
use rustc_lint::{LateContext, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::{self, FloatTy, InferTy, Ty};
use super::UNNECESSARY_CAST;
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &Expr<'tcx>,
cast_expr: &Expr<'tcx>,
cast_from: Ty<'tcx>,
cast_to: Ty<'tcx>,
) -> bool {
// skip non-primitive type cast
if_chain! {
if let ExprKind::Cast(_, cast_to) = expr.kind;
if let TyKind::Path(QPath::Resolved(_, path)) = &cast_to.kind;
if let Res::PrimTy(_) = path.res;
then {}
else {
return false
}
}
if let Some(lit) = get_numeric_literal(cast_expr) {
let literal_str = snippet_opt(cx, cast_expr.span).unwrap_or_default();
if_chain! {
if let LitKind::Int(n, _) = lit.node;
if let Some(src) = snippet_opt(cx, cast_expr.span);
if cast_to.is_floating_point();
if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node);
let from_nbits = 128 - n.leading_zeros();
let to_nbits = fp_ty_mantissa_nbits(cast_to);
if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits && num_lit.is_decimal();
then {
lint_unnecessary_cast(cx, expr, num_lit.integer, cast_from, cast_to);
return true
}
}
match lit.node {
LitKind::Int(_, LitIntType::Unsuffixed) if cast_to.is_integral() => {
lint_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
},
LitKind::Float(_, LitFloatType::Unsuffixed) if cast_to.is_floating_point() => {
lint_unnecessary_cast(cx, expr, &literal_str, cast_from, cast_to);
},
LitKind::Int(_, LitIntType::Unsuffixed) | LitKind::Float(_, LitFloatType::Unsuffixed) => {},
LitKind::Int(_, LitIntType::Signed(_) | LitIntType::Unsigned(_))
| LitKind::Float(_, LitFloatType::Suffixed(_))
if cast_from.kind() == cast_to.kind() =>
{
if let Some(src) = snippet_opt(cx, cast_expr.span) {
if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node) {
lint_unnecessary_cast(cx, expr, num_lit.integer, cast_from, cast_to);
}
}
},
_ => {
if cast_from.kind() == cast_to.kind() && !in_external_macro(cx.sess(), expr.span) {
span_lint_and_sugg(
cx,
UNNECESSARY_CAST,
expr.span,
&format!(
"casting to the same type is unnecessary (`{}` -> `{}`)",
cast_from, cast_to
),
"try",
literal_str,
Applicability::MachineApplicable,
);
return true;
}
},
}
}
false
}
fn lint_unnecessary_cast(cx: &LateContext<'_>, expr: &Expr<'_>, literal_str: &str, cast_from: Ty<'_>, cast_to: Ty<'_>) {
let literal_kind_name = if cast_from.is_integral() { "integer" } else { "float" };
span_lint_and_sugg(
cx,
UNNECESSARY_CAST,
expr.span,
&format!("casting {} literal to `{}` is unnecessary", literal_kind_name, cast_to),
"try",
format!("{}_{}", literal_str.trim_end_matches('.'), cast_to),
Applicability::MachineApplicable,
);
}
fn get_numeric_literal<'e>(expr: &'e Expr<'e>) -> Option<&'e Lit> {
match expr.kind {
ExprKind::Lit(ref lit) => Some(lit),
ExprKind::Unary(UnOp::Neg, e) => {
if let ExprKind::Lit(ref lit) = e.kind {
Some(lit)
} else {
None
}
},
_ => None,
}
}
/// Returns the mantissa bits wide of a fp type.
/// Will return 0 if the type is not a fp
fn fp_ty_mantissa_nbits(typ: Ty<'_>) -> u32 {
match typ.kind() {
ty::Float(FloatTy::F32) => 23,
ty::Float(FloatTy::F64) | ty::Infer(InferTy::FloatVar(_)) => 52,
_ => 0,
}
}
|
