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//! Lint for `some_result_or_option.unwrap_or_else(Default::default)`
use super::UNWRAP_OR_ELSE_DEFAULT;
use clippy_utils::{
diagnostics::span_lint_and_sugg, is_default_equivalent_call, source::snippet_with_applicability,
ty::is_type_diagnostic_item,
};
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_span::{sym, symbol};
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx hir::Expr<'_>,
recv: &'tcx hir::Expr<'_>,
u_arg: &'tcx hir::Expr<'_>,
) {
// something.unwrap_or_else(Default::default)
// ^^^^^^^^^- recv ^^^^^^^^^^^^^^^^- u_arg
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^- expr
let recv_ty = cx.typeck_results().expr_ty(recv);
let is_option = is_type_diagnostic_item(cx, recv_ty, sym::Option);
let is_result = is_type_diagnostic_item(cx, recv_ty, sym::Result);
if_chain! {
if is_option || is_result;
if closure_body_returns_empty_to_string(cx, u_arg) || is_default_equivalent_call(cx, u_arg);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
UNWRAP_OR_ELSE_DEFAULT,
expr.span,
"use of `.unwrap_or_else(..)` to construct default value",
"try",
format!(
"{}.unwrap_or_default()",
snippet_with_applicability(cx, recv.span, "..", &mut applicability)
),
applicability,
);
}
}
}
fn closure_body_returns_empty_to_string(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> bool {
if let hir::ExprKind::Closure(&hir::Closure { body, .. }) = e.kind {
let body = cx.tcx.hir().body(body);
if body.params.is_empty()
&& let hir::Expr{ kind, .. } = &body.value
&& let hir::ExprKind::MethodCall(hir::PathSegment {ident, ..}, self_arg, _, _) = kind
&& ident == &symbol::Ident::from_str("to_string")
&& let hir::Expr{ kind, .. } = self_arg
&& let hir::ExprKind::Lit(lit) = kind
&& let LitKind::Str(symbol::kw::Empty, _) = lit.node
{
return true;
}
}
false
}
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