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|
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::{contains_return, is_res_lang_ctor, path_res, return_ty, visitors::find_all_ret_expressions};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::intravisit::FnKind;
use rustc_hir::LangItem::{OptionSome, ResultOk};
use rustc_hir::{Body, ExprKind, FnDecl, HirId, Impl, ItemKind, Node};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::symbol::sym;
use rustc_span::Span;
declare_clippy_lint! {
/// ### What it does
/// Checks for private functions that only return `Ok` or `Some`.
///
/// ### Why is this bad?
/// It is not meaningful to wrap values when no `None` or `Err` is returned.
///
/// ### Known problems
/// There can be false positives if the function signature is designed to
/// fit some external requirement.
///
/// ### Example
/// ```rust
/// fn get_cool_number(a: bool, b: bool) -> Option<i32> {
/// if a && b {
/// return Some(50);
/// }
/// if a {
/// Some(0)
/// } else {
/// Some(10)
/// }
/// }
/// ```
/// Use instead:
/// ```rust
/// fn get_cool_number(a: bool, b: bool) -> i32 {
/// if a && b {
/// return 50;
/// }
/// if a {
/// 0
/// } else {
/// 10
/// }
/// }
/// ```
#[clippy::version = "1.50.0"]
pub UNNECESSARY_WRAPS,
pedantic,
"functions that only return `Ok` or `Some`"
}
pub struct UnnecessaryWraps {
avoid_breaking_exported_api: bool,
}
impl_lint_pass!(UnnecessaryWraps => [UNNECESSARY_WRAPS]);
impl UnnecessaryWraps {
pub fn new(avoid_breaking_exported_api: bool) -> Self {
Self {
avoid_breaking_exported_api,
}
}
}
impl<'tcx> LateLintPass<'tcx> for UnnecessaryWraps {
fn check_fn(
&mut self,
cx: &LateContext<'tcx>,
fn_kind: FnKind<'tcx>,
fn_decl: &FnDecl<'tcx>,
body: &Body<'tcx>,
span: Span,
hir_id: HirId,
) {
// Abort if public function/method or closure.
match fn_kind {
FnKind::ItemFn(..) | FnKind::Method(..) => {
let def_id = cx.tcx.hir().local_def_id(hir_id);
if self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(def_id) {
return;
}
},
FnKind::Closure => return,
}
// Abort if the method is implementing a trait or of it a trait method.
if let Some(Node::Item(item)) = cx.tcx.hir().find_parent(hir_id) {
if matches!(
item.kind,
ItemKind::Impl(Impl { of_trait: Some(_), .. }) | ItemKind::Trait(..)
) {
return;
}
}
// Get the wrapper and inner types, if can't, abort.
let (return_type_label, lang_item, inner_type) = if let ty::Adt(adt_def, subst) = return_ty(cx, hir_id).kind() {
if cx.tcx.is_diagnostic_item(sym::Option, adt_def.did()) {
("Option", OptionSome, subst.type_at(0))
} else if cx.tcx.is_diagnostic_item(sym::Result, adt_def.did()) {
("Result", ResultOk, subst.type_at(0))
} else {
return;
}
} else {
return;
};
// Check if all return expression respect the following condition and collect them.
let mut suggs = Vec::new();
let can_sugg = find_all_ret_expressions(cx, body.value, |ret_expr| {
if_chain! {
if !ret_expr.span.from_expansion();
// Check if a function call.
if let ExprKind::Call(func, [arg]) = ret_expr.kind;
if is_res_lang_ctor(cx, path_res(cx, func), lang_item);
// Make sure the function argument does not contain a return expression.
if !contains_return(arg);
then {
suggs.push(
(
ret_expr.span,
if inner_type.is_unit() {
String::new()
} else {
snippet(cx, arg.span.source_callsite(), "..").to_string()
}
)
);
true
} else {
false
}
}
});
if can_sugg && !suggs.is_empty() {
let (lint_msg, return_type_sugg_msg, return_type_sugg, body_sugg_msg) = if inner_type.is_unit() {
(
"this function's return value is unnecessary".to_string(),
"remove the return type...".to_string(),
snippet(cx, fn_decl.output.span(), "..").to_string(),
"...and then remove returned values",
)
} else {
(
format!("this function's return value is unnecessarily wrapped by `{return_type_label}`"),
format!("remove `{return_type_label}` from the return type..."),
inner_type.to_string(),
"...and then change returning expressions",
)
};
span_lint_and_then(cx, UNNECESSARY_WRAPS, span, lint_msg.as_str(), |diag| {
diag.span_suggestion(
fn_decl.output.span(),
return_type_sugg_msg.as_str(),
return_type_sugg,
Applicability::MaybeIncorrect,
);
diag.multipart_suggestion(body_sugg_msg, suggs, Applicability::MaybeIncorrect);
});
}
}
}
|
