rust-clippy/clippy_lints/src/methods/unnecessary_lazy_eval.rs

53 lines
1.9 KiB
Rust

use crate::utils::{eager_or_lazy, usage};
use crate::utils::{is_type_diagnostic_item, snippet, span_lint_and_sugg};
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use super::UNNECESSARY_LAZY_EVALUATIONS;
/// lint use of `<fn>_else(simple closure)` for `Option`s and `Result`s that can be
/// replaced with `<fn>(return value of simple closure)`
pub(super) fn lint<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx hir::Expr<'_>,
args: &'tcx [hir::Expr<'_>],
simplify_using: &str,
) {
let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&args[0]), sym!(option_type));
let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&args[0]), sym!(result_type));
if is_option || is_result {
if let hir::ExprKind::Closure(_, _, eid, _, _) = args[1].kind {
let body = cx.tcx.hir().body(eid);
let body_expr = &body.value;
if usage::BindingUsageFinder::are_params_used(cx, body) {
return;
}
if eager_or_lazy::is_eagerness_candidate(cx, body_expr) {
let msg = if is_option {
"unnecessary closure used to substitute value for `Option::None`"
} else {
"unnecessary closure used to substitute value for `Result::Err`"
};
span_lint_and_sugg(
cx,
UNNECESSARY_LAZY_EVALUATIONS,
expr.span,
msg,
&format!("Use `{}` instead", simplify_using),
format!(
"{0}.{1}({2})",
snippet(cx, args[0].span, ".."),
simplify_using,
snippet(cx, body_expr.span, ".."),
),
Applicability::MachineApplicable,
);
}
}
}
}