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Implemented needless question mark lint
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,232 @@ | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res}; | ||
| use rustc_hir::{Body, Expr, ExprKind, LangItem, MatchSource, QPath}; | ||
| use rustc_lint::{LateContext, LateLintPass, LintContext}; | ||
| use rustc_middle::ty::DefIdTree; | ||
| use rustc_semver::RustcVersion; | ||
| use rustc_session::{declare_tool_lint, impl_lint_pass}; | ||
| use rustc_span::sym; | ||
|
|
||
| use crate::utils; | ||
| use if_chain::if_chain; | ||
|
|
||
| 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. | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// | ||
| /// ```rust | ||
| /// struct TO { | ||
| /// magic: Option<usize>, | ||
| /// } | ||
| /// | ||
| /// fn f(to: TO) -> Option<usize> { | ||
| /// return Some(to.magic?); | ||
| /// } | ||
| /// | ||
| /// struct TR { | ||
| /// magic: Result<usize, bool>, | ||
| /// } | ||
| /// | ||
| /// fn g(tr: Result<TR, bool>) -> Result<usize, bool> { | ||
| /// return 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>." | ||
| } | ||
|
|
||
| const NEEDLESS_QUESTION_MARK_RESULT_MSRV: RustcVersion = RustcVersion::new(1, 13, 0); | ||
| const NEEDLESS_QUESTION_MARK_OPTION_MSRV: RustcVersion = RustcVersion::new(1, 22, 0); | ||
|
|
||
| pub struct NeedlessQuestionMark { | ||
| msrv: Option<RustcVersion>, | ||
| } | ||
|
|
||
| impl NeedlessQuestionMark { | ||
| #[must_use] | ||
| pub fn new(msrv: Option<RustcVersion>) -> Self { | ||
| Self { msrv } | ||
| } | ||
| } | ||
|
|
||
| impl_lint_pass!(NeedlessQuestionMark => [NEEDLESS_QUESTION_MARK]); | ||
|
|
||
| #[derive(Debug)] | ||
| enum SomeOkCall<'a> { | ||
| SomeCall(&'a Expr<'a>, &'a Expr<'a>), | ||
| OkCall(&'a Expr<'a>, &'a Expr<'a>), | ||
| } | ||
|
|
||
| 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<'_>) { | ||
| let e = match &expr.kind { | ||
| ExprKind::Ret(Some(e)) => e, | ||
| _ => return, | ||
| }; | ||
|
|
||
| if let Some(ok_some_call) = is_some_or_ok_call(self, cx, e) { | ||
| emit_lint(cx, &ok_some_call); | ||
| } | ||
| } | ||
|
|
||
| fn check_body(&mut self, cx: &LateContext<'_>, body: &'_ Body<'_>) { | ||
| // Function / Closure block | ||
| let expr_opt = if let ExprKind::Block(block, _) = &body.value.kind { | ||
| block.expr | ||
| } else { | ||
| // Single line closure | ||
| Some(&body.value) | ||
| }; | ||
|
|
||
| if_chain! { | ||
| if let Some(expr) = expr_opt; | ||
| if let Some(ok_some_call) = is_some_or_ok_call(self, cx, expr); | ||
| then { | ||
| emit_lint(cx, &ok_some_call); | ||
| } | ||
| }; | ||
| } | ||
|
|
||
| extract_msrv_attr!(LateContext); | ||
| } | ||
|
|
||
| fn emit_lint(cx: &LateContext<'_>, expr: &SomeOkCall<'_>) { | ||
| let (entire_expr, inner_expr) = match expr { | ||
| SomeOkCall::OkCall(outer, inner) | SomeOkCall::SomeCall(outer, inner) => (outer, inner), | ||
| }; | ||
|
|
||
| utils::span_lint_and_sugg( | ||
| cx, | ||
| NEEDLESS_QUESTION_MARK, | ||
| entire_expr.span, | ||
| "Question mark operator is useless here", | ||
| "try", | ||
| format!("{}", utils::snippet(cx, inner_expr.span, r#""...""#)), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
|
|
||
| fn is_some_or_ok_call<'a>( | ||
| nqml: &NeedlessQuestionMark, | ||
| cx: &'a LateContext<'_>, | ||
| expr: &'a Expr<'_>, | ||
| ) -> Option<SomeOkCall<'a>> { | ||
| if_chain! { | ||
| // Check outer expression matches CALL_IDENT(ARGUMENT) format | ||
| if let ExprKind::Call(path, args) = &expr.kind; | ||
| if let ExprKind::Path(QPath::Resolved(None, path)) = &path.kind; | ||
| if is_some_ctor(cx, path.res) || is_ok_ctor(cx, path.res); | ||
|
|
||
| // Extract inner expression from ARGUMENT | ||
| if let ExprKind::Match(inner_expr_with_q, _, MatchSource::TryDesugar) = &args[0].kind; | ||
| if let ExprKind::Call(called, args) = &inner_expr_with_q.kind; | ||
| if args.len() == 1; | ||
|
|
||
| if let ExprKind::Path(QPath::LangItem(LangItem::TryIntoResult, _)) = &called.kind; | ||
| then { | ||
| // Extract inner expr type from match argument generated by | ||
| // question mark operator | ||
| let inner_expr = &args[0]; | ||
|
|
||
| let inner_ty = cx.typeck_results().expr_ty(inner_expr); | ||
| let outer_ty = cx.typeck_results().expr_ty(expr); | ||
|
|
||
| // Check if outer and inner type are Option | ||
| let outer_is_some = utils::is_type_diagnostic_item(cx, outer_ty, sym::option_type); | ||
| let inner_is_some = utils::is_type_diagnostic_item(cx, inner_ty, sym::option_type); | ||
|
|
||
| // Check for Option MSRV | ||
| let meets_option_msrv = utils::meets_msrv(nqml.msrv.as_ref(), &NEEDLESS_QUESTION_MARK_OPTION_MSRV); | ||
| if outer_is_some && inner_is_some && meets_option_msrv { | ||
| return Some(SomeOkCall::SomeCall(expr, inner_expr)); | ||
| } | ||
|
|
||
| // Check if outer and inner type are Result | ||
| let outer_is_result = utils::is_type_diagnostic_item(cx, outer_ty, sym::result_type); | ||
| let inner_is_result = utils::is_type_diagnostic_item(cx, inner_ty, sym::result_type); | ||
|
|
||
| // Additional check: if the error type of the Result can be converted | ||
| // via the From trait, then don't match | ||
| let does_not_call_from = !has_implicit_error_from(cx, expr, inner_expr); | ||
|
|
||
| // Must meet Result MSRV | ||
| let meets_result_msrv = utils::meets_msrv(nqml.msrv.as_ref(), &NEEDLESS_QUESTION_MARK_RESULT_MSRV); | ||
| if outer_is_result && inner_is_result && does_not_call_from && meets_result_msrv { | ||
| return Some(SomeOkCall::OkCall(expr, inner_expr)); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| None | ||
| } | ||
|
|
||
| fn has_implicit_error_from(cx: &LateContext<'_>, entire_expr: &Expr<'_>, inner_result_expr: &Expr<'_>) -> bool { | ||
| return cx.typeck_results().expr_ty(entire_expr) != cx.typeck_results().expr_ty(inner_result_expr); | ||
| } | ||
|
|
||
| fn is_ok_ctor(cx: &LateContext<'_>, res: Res) -> bool { | ||
| if let Some(ok_id) = cx.tcx.lang_items().result_ok_variant() { | ||
| if let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Fn), id) = res { | ||
| if let Some(variant_id) = cx.tcx.parent(id) { | ||
| return variant_id == ok_id; | ||
| } | ||
| } | ||
| } | ||
| false | ||
| } | ||
|
|
||
| fn is_some_ctor(cx: &LateContext<'_>, res: Res) -> bool { | ||
| if let Some(some_id) = cx.tcx.lang_items().option_some_variant() { | ||
| if let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Fn), id) = res { | ||
| if let Some(variant_id) = cx.tcx.parent(id) { | ||
| return variant_id == some_id; | ||
| } | ||
| } | ||
| } | ||
| false | ||
| } |
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