1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::source::snippet;
3 use clippy_utils::{contains_return, in_macro, is_lang_ctor, return_ty, visitors::find_all_ret_expressions};
4 use if_chain::if_chain;
5 use rustc_errors::Applicability;
6 use rustc_hir::intravisit::FnKind;
7 use rustc_hir::LangItem::{OptionSome, ResultOk};
8 use rustc_hir::{Body, ExprKind, FnDecl, HirId, Impl, ItemKind, Node};
9 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_session::{declare_tool_lint, impl_lint_pass};
12 use rustc_span::symbol::sym;
15 declare_clippy_lint! {
16 /// **What it does:** Checks for private functions that only return `Ok` or `Some`.
18 /// **Why is this bad?** It is not meaningful to wrap values when no `None` or `Err` is returned.
20 /// **Known problems:** There can be false positives if the function signature is designed to
21 /// fit some external requirement.
26 /// fn get_cool_number(a: bool, b: bool) -> Option<i32> {
39 /// fn get_cool_number(a: bool, b: bool) -> i32 {
50 pub UNNECESSARY_WRAPS,
52 "functions that only return `Ok` or `Some`"
55 pub struct UnnecessaryWraps {
56 avoid_breaking_exported_api: bool,
59 impl_lint_pass!(UnnecessaryWraps => [UNNECESSARY_WRAPS]);
61 impl UnnecessaryWraps {
62 pub fn new(avoid_breaking_exported_api: bool) -> Self {
64 avoid_breaking_exported_api,
69 impl<'tcx> LateLintPass<'tcx> for UnnecessaryWraps {
72 cx: &LateContext<'tcx>,
73 fn_kind: FnKind<'tcx>,
74 fn_decl: &FnDecl<'tcx>,
79 // Abort if public function/method or closure.
81 FnKind::ItemFn(..) | FnKind::Method(..) => {
82 if self.avoid_breaking_exported_api && cx.access_levels.is_exported(hir_id) {
86 FnKind::Closure => return,
89 // Abort if the method is implementing a trait or of it a trait method.
90 if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) {
93 ItemKind::Impl(Impl { of_trait: Some(_), .. }) | ItemKind::Trait(..)
99 // Get the wrapper and inner types, if can't, abort.
100 let (return_type_label, lang_item, inner_type) = if let ty::Adt(adt_def, subst) = return_ty(cx, hir_id).kind() {
101 if cx.tcx.is_diagnostic_item(sym::option_type, adt_def.did) {
102 ("Option", OptionSome, subst.type_at(0))
103 } else if cx.tcx.is_diagnostic_item(sym::result_type, adt_def.did) {
104 ("Result", ResultOk, subst.type_at(0))
112 // Check if all return expression respect the following condition and collect them.
113 let mut suggs = Vec::new();
114 let can_sugg = find_all_ret_expressions(cx, &body.value, |ret_expr| {
116 if !in_macro(ret_expr.span);
117 // Check if a function call.
118 if let ExprKind::Call(func, [arg]) = ret_expr.kind;
119 // Check if OPTION_SOME or RESULT_OK, depending on return type.
120 if let ExprKind::Path(qpath) = &func.kind;
121 if is_lang_ctor(cx, qpath, lang_item);
122 // Make sure the function argument does not contain a return expression.
123 if !contains_return(arg);
128 if inner_type.is_unit() {
131 snippet(cx, arg.span.source_callsite(), "..").to_string()
142 if can_sugg && !suggs.is_empty() {
143 let (lint_msg, return_type_sugg_msg, return_type_sugg, body_sugg_msg) = if inner_type.is_unit() {
145 "this function's return value is unnecessary".to_string(),
146 "remove the return type...".to_string(),
147 snippet(cx, fn_decl.output.span(), "..").to_string(),
148 "...and then remove returned values",
153 "this function's return value is unnecessarily wrapped by `{}`",
156 format!("remove `{}` from the return type...", return_type_label),
157 inner_type.to_string(),
158 "...and then change returning expressions",
162 span_lint_and_then(cx, UNNECESSARY_WRAPS, span, lint_msg.as_str(), |diag| {
163 diag.span_suggestion(
164 fn_decl.output.span(),
165 return_type_sugg_msg.as_str(),
167 Applicability::MaybeIncorrect,
169 diag.multipart_suggestion(body_sugg_msg, suggs, Applicability::MaybeIncorrect);