rust/clippy_lints/src/methods/option_map_or_none.rs

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use crate::utils::{is_type_diagnostic_item, match_qpath, paths, snippet, span_lint_and_sugg};
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_span::symbol::sym;
use super::OPTION_MAP_OR_NONE;
use super::RESULT_MAP_OR_INTO_OPTION;
/// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, map_or_args: &'tcx [hir::Expr<'_>]) {
let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::option_type);
let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&map_or_args[0]), sym::result_type);
// There are two variants of this `map_or` lint:
// (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
// (2) using `map_or` as a combinator instead of `and_then`
//
// (For this lint) we don't care if any other type calls `map_or`
if !is_option && !is_result {
return;
}
let (lint_name, msg, instead, hint) = {
let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
match_qpath(qpath, &paths::OPTION_NONE)
} else {
return;
};
if !default_arg_is_none {
// nothing to lint!
return;
}
let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_or_args[2].kind {
match_qpath(qpath, &paths::OPTION_SOME)
} else {
false
};
if is_option {
let self_snippet = snippet(cx, map_or_args[0].span, "..");
let func_snippet = snippet(cx, map_or_args[2].span, "..");
let msg = "called `map_or(None, ..)` on an `Option` value. This can be done more directly by calling \
`and_then(..)` instead";
(
OPTION_MAP_OR_NONE,
msg,
"try using `and_then` instead",
format!("{0}.and_then({1})", self_snippet, func_snippet),
)
} else if f_arg_is_some {
let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
`ok()` instead";
let self_snippet = snippet(cx, map_or_args[0].span, "..");
(
RESULT_MAP_OR_INTO_OPTION,
msg,
"try using `ok` instead",
format!("{0}.ok()", self_snippet),
)
} else {
// nothing to lint!
return;
}
};
span_lint_and_sugg(
cx,
lint_name,
expr.span,
msg,
instead,
hint,
Applicability::MachineApplicable,
);
}