118 lines
3.6 KiB
Rust
118 lines
3.6 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
|
|
use clippy_utils::is_lang_ctor;
|
|
use clippy_utils::source::snippet;
|
|
use if_chain::if_chain;
|
|
use rustc_errors::Applicability;
|
|
use rustc_hir::LangItem::{OptionSome, ResultOk};
|
|
use rustc_hir::{Body, Expr, ExprKind, LangItem, MatchSource, QPath};
|
|
use rustc_lint::{LateContext, LateLintPass};
|
|
use rustc_middle::ty::TyS;
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
|
|
|
declare_clippy_lint! {
|
|
/// ### What it does
|
|
/// Suggests alternatives for useless applications of `?` in terminating expressions
|
|
///
|
|
/// ### Why is this bad?
|
|
/// There's no reason to use `?` to short-circuit when execution of the body will end there anyway.
|
|
///
|
|
/// ### Example
|
|
/// ```rust
|
|
/// struct TO {
|
|
/// magic: Option<usize>,
|
|
/// }
|
|
///
|
|
/// fn f(to: TO) -> Option<usize> {
|
|
/// Some(to.magic?)
|
|
/// }
|
|
///
|
|
/// struct TR {
|
|
/// magic: Result<usize, bool>,
|
|
/// }
|
|
///
|
|
/// fn g(tr: Result<TR, bool>) -> Result<usize, bool> {
|
|
/// tr.and_then(|t| Ok(t.magic?))
|
|
/// }
|
|
///
|
|
/// ```
|
|
/// Use instead:
|
|
/// ```rust
|
|
/// struct TO {
|
|
/// magic: Option<usize>,
|
|
/// }
|
|
///
|
|
/// fn f(to: TO) -> Option<usize> {
|
|
/// to.magic
|
|
/// }
|
|
///
|
|
/// struct TR {
|
|
/// magic: Result<usize, bool>,
|
|
/// }
|
|
///
|
|
/// fn g(tr: Result<TR, bool>) -> Result<usize, bool> {
|
|
/// tr.and_then(|t| t.magic)
|
|
/// }
|
|
/// ```
|
|
pub NEEDLESS_QUESTION_MARK,
|
|
complexity,
|
|
"Suggest `value.inner_option` instead of `Some(value.inner_option?)`. The same goes for `Result<T, E>`."
|
|
}
|
|
|
|
declare_lint_pass!(NeedlessQuestionMark => [NEEDLESS_QUESTION_MARK]);
|
|
|
|
impl LateLintPass<'_> for NeedlessQuestionMark {
|
|
/*
|
|
* The question mark operator is compatible with both Result<T, E> and Option<T>,
|
|
* from Rust 1.13 and 1.22 respectively.
|
|
*/
|
|
|
|
/*
|
|
* What do we match:
|
|
* Expressions that look like this:
|
|
* Some(option?), Ok(result?)
|
|
*
|
|
* Where do we match:
|
|
* Last expression of a body
|
|
* Return statement
|
|
* A body's value (single line closure)
|
|
*
|
|
* What do we not match:
|
|
* Implicit calls to `from(..)` on the error value
|
|
*/
|
|
|
|
fn check_expr(&mut self, cx: &LateContext<'_>, expr: &'_ Expr<'_>) {
|
|
if let ExprKind::Ret(Some(e)) = expr.kind {
|
|
check(cx, e);
|
|
}
|
|
}
|
|
|
|
fn check_body(&mut self, cx: &LateContext<'_>, body: &'_ Body<'_>) {
|
|
check(cx, body.value.peel_blocks());
|
|
}
|
|
}
|
|
|
|
fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
|
|
let inner_expr = if_chain! {
|
|
if let ExprKind::Call(path, [arg]) = &expr.kind;
|
|
if let ExprKind::Path(ref qpath) = &path.kind;
|
|
if is_lang_ctor(cx, qpath, OptionSome) || is_lang_ctor(cx, qpath, ResultOk);
|
|
if let ExprKind::Match(inner_expr_with_q, _, MatchSource::TryDesugar) = &arg.kind;
|
|
if let ExprKind::Call(called, [inner_expr]) = &inner_expr_with_q.kind;
|
|
if let ExprKind::Path(QPath::LangItem(LangItem::TryTraitBranch, _)) = &called.kind;
|
|
if expr.span.ctxt() == inner_expr.span.ctxt();
|
|
let expr_ty = cx.typeck_results().expr_ty(expr);
|
|
let inner_ty = cx.typeck_results().expr_ty(inner_expr);
|
|
if TyS::same_type(expr_ty, inner_ty);
|
|
then { inner_expr } else { return; }
|
|
};
|
|
span_lint_and_sugg(
|
|
cx,
|
|
NEEDLESS_QUESTION_MARK,
|
|
expr.span,
|
|
"question mark operator is useless here",
|
|
"try",
|
|
format!("{}", snippet(cx, inner_expr.span, r#""...""#)),
|
|
Applicability::MachineApplicable,
|
|
);
|
|
}
|