1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::source::snippet;
3 use clippy_utils::ty::is_type_diagnostic_item;
4 use clippy_utils::{is_lang_ctor, path_def_id};
5 use rustc_errors::Applicability;
7 use rustc_hir::LangItem::{OptionNone, OptionSome};
8 use rustc_lint::LateContext;
9 use rustc_middle::ty::DefIdTree;
10 use rustc_span::symbol::sym;
12 use super::OPTION_MAP_OR_NONE;
13 use super::RESULT_MAP_OR_INTO_OPTION;
15 // The expression inside a closure may or may not have surrounding braces
16 // which causes problems when generating a suggestion.
17 fn reduce_unit_expression<'a>(
19 expr: &'a hir::Expr<'_>,
20 ) -> Option<(&'a hir::Expr<'a>, &'a [hir::Expr<'a>])> {
22 hir::ExprKind::Call(func, arg_char) => Some((func, arg_char)),
23 hir::ExprKind::Block(block, _) => {
24 match (block.stmts, block.expr) {
25 (&[], Some(inner_expr)) => {
26 // If block only contains an expression,
27 // reduce `|x| { x + 1 }` to `|x| x + 1`
28 reduce_unit_expression(cx, inner_expr)
37 /// lint use of `_.map_or(None, _)` for `Option`s and `Result`s
38 pub(super) fn check<'tcx>(
39 cx: &LateContext<'tcx>,
40 expr: &'tcx hir::Expr<'_>,
41 recv: &'tcx hir::Expr<'_>,
42 def_arg: &'tcx hir::Expr<'_>,
43 map_arg: &'tcx hir::Expr<'_>,
45 let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option);
46 let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result);
48 // There are two variants of this `map_or` lint:
49 // (1) using `map_or` as an adapter from `Result<T,E>` to `Option<T>`
50 // (2) using `map_or` as a combinator instead of `and_then`
52 // (For this lint) we don't care if any other type calls `map_or`
53 if !is_option && !is_result {
57 let default_arg_is_none = if let hir::ExprKind::Path(ref qpath) = def_arg.kind {
58 is_lang_ctor(cx, qpath, OptionNone)
63 if !default_arg_is_none {
68 let f_arg_is_some = if let hir::ExprKind::Path(ref qpath) = map_arg.kind {
69 is_lang_ctor(cx, qpath, OptionSome)
75 let self_snippet = snippet(cx, recv.span, "..");
77 if let hir::ExprKind::Closure(_, _, id, span, _) = map_arg.kind;
78 let arg_snippet = snippet(cx, span, "..");
79 let body = cx.tcx.hir().body(id);
80 if let Some((func, [arg_char])) = reduce_unit_expression(cx, &body.value);
81 if let Some(id) = path_def_id(cx, func).and_then(|ctor_id| cx.tcx.parent(ctor_id));
82 if Some(id) == cx.tcx.lang_items().option_some_variant();
84 let func_snippet = snippet(cx, arg_char.span, "..");
85 let msg = "called `map_or(None, ..)` on an `Option` value. This can be done more directly by calling \
87 return span_lint_and_sugg(
92 "try using `map` instead",
93 format!("{0}.map({1} {2})", self_snippet, arg_snippet,func_snippet),
94 Applicability::MachineApplicable,
100 let func_snippet = snippet(cx, map_arg.span, "..");
101 let msg = "called `map_or(None, ..)` on an `Option` value. This can be done more directly by calling \
102 `and_then(..)` instead";
103 return span_lint_and_sugg(
108 "try using `and_then` instead",
109 format!("{0}.and_then({1})", self_snippet, func_snippet),
110 Applicability::MachineApplicable,
112 } else if f_arg_is_some {
113 let msg = "called `map_or(None, Some)` on a `Result` value. This can be done more directly by calling \
115 let self_snippet = snippet(cx, recv.span, "..");
116 return span_lint_and_sugg(
118 RESULT_MAP_OR_INTO_OPTION,
121 "try using `ok` instead",
122 format!("{0}.ok()", self_snippet),
123 Applicability::MachineApplicable,