Add unneeded_try_convert lint
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| Original file line number | Diff line number | Diff line change | ||||
|---|---|---|---|---|---|---|
| @@ -0,0 +1,235 @@ | ||||||
| use crate::utils::{ | ||||||
| is_ctor_or_promotable_const_function, match_def_path, match_type, paths, snippet_with_applicability, | ||||||
| span_lint_and_then, | ||||||
| }; | ||||||
| use if_chain::if_chain; | ||||||
| use rustc::hir::intravisit::Visitor; | ||||||
| use rustc::hir::{self, *}; | ||||||
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; | ||||||
| use rustc::ty::Ty; | ||||||
| use rustc::{declare_lint_pass, declare_tool_lint}; | ||||||
| use rustc_errors::Applicability; | ||||||
| use syntax_pos::Span; | ||||||
|
|
||||||
| declare_clippy_lint! { | ||||||
| /// **What it does:** Checks for usages of `option.ok_or_else(|| <..>::from(..))?` or | ||||||
| /// `result.map_err(|x| <..>::from(..))`. | ||||||
| /// | ||||||
| /// **Why is this bad?** The `?` operator will call `from` in the `Err` case, | ||||||
| /// so calling it manually is redundant. | ||||||
| /// | ||||||
| /// **Known problems:** The suggested fix does not correct any explicitly provided | ||||||
| /// type arguments in `ok_or_else` or `map_err`. | ||||||
| /// | ||||||
| /// **Example:** | ||||||
| /// ```rust | ||||||
| /// fn bar() -> Result<i32, String> { | ||||||
| /// let x = Some(52.3).ok_or_else(|| String::from("foo"))?; | ||||||
| /// Ok(42) | ||||||
| /// } | ||||||
| /// ``` | ||||||
| /// Could be written: | ||||||
| /// | ||||||
| /// ```rust | ||||||
| /// fn bar() -> Result<i32, String> { | ||||||
| /// let x = Some(52.3).ok_or("foo")?; | ||||||
| /// Ok(42) | ||||||
| /// } | ||||||
| /// ``` | ||||||
| pub UNNEEDED_TRY_CONVERT, | ||||||
| complexity, | ||||||
| "unneeded conversion inside `?`" | ||||||
| } | ||||||
|
|
||||||
| declare_lint_pass!(UnneededTryConvert => [UNNEEDED_TRY_CONVERT]); | ||||||
|
|
||||||
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnneededTryConvert { | ||||||
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { | ||||||
| if_chain! { | ||||||
| if let ExprKind::Match(match_arg, arms, MatchSource::TryDesugar) = &expr.kind; | ||||||
| if let ExprKind::Call(_, args) = &match_arg.kind; | ||||||
| if let [try_arg] = &**args; | ||||||
| if let Some(fn_error_ty) = get_try_err_ty(cx, arms); | ||||||
| then { | ||||||
| check_option_ok_or_else(cx, fn_error_ty, try_arg); | ||||||
| check_result_map_err(cx, fn_error_ty, try_arg); | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
|
|
||||||
| /// Given the arms of a `match` expr from desugaring a `?`, return the error type of the `Try` type | ||||||
| fn get_try_err_ty<'tcx>(cx: &LateContext<'_, 'tcx>, match_arms: &[Arm]) -> Option<Ty<'tcx>> { | ||||||
| if_chain! { | ||||||
| if let [err_arm, _] = match_arms; | ||||||
| if let ExprKind::Ret(Some(ret_expr)) = &err_arm.body.kind; | ||||||
| if let ExprKind::Call(_, try_from_error_args) = &ret_expr.kind; | ||||||
| if let [try_from_error_arg] = &**try_from_error_args; | ||||||
| then { | ||||||
| return Some(cx.tables.expr_ty(try_from_error_arg)); | ||||||
| } | ||||||
| } | ||||||
| None | ||||||
| } | ||||||
|
|
||||||
| fn check_option_ok_or_else<'tcx>(cx: &LateContext<'_, 'tcx>, fn_error_ty: Ty<'tcx>, expr: &Expr) { | ||||||
| if_chain! { | ||||||
| if let ExprKind::MethodCall(call_path, _, call_args) = &expr.kind; | ||||||
| if call_path.ident.as_str() == "ok_or_else"; | ||||||
| if let [receiver, closure_expr] = &**call_args; | ||||||
| if match_type(cx, cx.tables.expr_ty(receiver), &paths::OPTION); | ||||||
| if let Some((closure_body_span, conv_arg)) = check_closure_expr(cx, fn_error_ty, closure_expr); | ||||||
| then { | ||||||
| let mut applicability = Applicability::MachineApplicable; | ||||||
| let conv_arg_snip = snippet_with_applicability(cx, conv_arg.span, "..", &mut applicability); | ||||||
| let (sugg_span, sugg_snip) = if is_trivial_expr(cx, conv_arg) { | ||||||
| // suggest inlining the closure and using `ok_or` | ||||||
| let receiver_snip = snippet_with_applicability(cx, receiver.span, "..", &mut applicability); | ||||||
| (expr.span, format!("{}.ok_or({})", receiver_snip, conv_arg_snip)) | ||||||
| } else { | ||||||
| // suggest removing the conversion in the closure | ||||||
| (closure_body_span, conv_arg_snip.into_owned()) | ||||||
| }; | ||||||
| emit_lint(cx, closure_body_span, sugg_span, sugg_snip, applicability); | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
|
|
||||||
| fn check_result_map_err<'tcx>(cx: &LateContext<'_, 'tcx>, fn_error_ty: Ty<'tcx>, expr: &Expr) { | ||||||
| if_chain! { | ||||||
| if let ExprKind::MethodCall(call_path, _, call_args) = &expr.kind; | ||||||
| if call_path.ident.as_str() == "map_err"; | ||||||
| if let [receiver, mapper_expr] = &**call_args; | ||||||
| let receiver_ty = cx.tables.expr_ty(receiver); | ||||||
| if match_type(cx, receiver_ty, &paths::RESULT); | ||||||
|
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Suggested change
|
||||||
| then { | ||||||
| if let Some((closure_body_span, conv_arg)) = check_closure_expr(cx, fn_error_ty, mapper_expr) { | ||||||
| // suggest removing just the conversion in the closure | ||||||
| let mut applicability = Applicability::MachineApplicable; | ||||||
| let conv_arg_snip = snippet_with_applicability(cx, conv_arg.span, "..", &mut applicability); | ||||||
| emit_lint( | ||||||
| cx, | ||||||
| closure_body_span, | ||||||
| closure_body_span, | ||||||
| conv_arg_snip.into_owned(), | ||||||
| applicability, | ||||||
| ); | ||||||
| return; | ||||||
| } | ||||||
| if_chain! { | ||||||
| if let ExprKind::Path(qpath) = &mapper_expr.kind; | ||||||
| if let def::Res::Def(_, def_id) = cx.tables.qpath_res(qpath, mapper_expr.hir_id); | ||||||
| if match_def_path(cx, def_id, &paths::FROM_FROM) | ||||||
| || match_def_path(cx, def_id, &paths::INTO_INTO); | ||||||
| if *cx.tables.expr_ty(mapper_expr).fn_sig(cx.tcx).output().skip_binder() == fn_error_ty; | ||||||
| then { | ||||||
| // suggest removing the entire `map_err(..)` call | ||||||
| let mut applicability = Applicability::MachineApplicable; | ||||||
| let receiver_snip = snippet_with_applicability(cx, receiver.span, "..", &mut applicability); | ||||||
| emit_lint( | ||||||
| cx, | ||||||
| mapper_expr.span, | ||||||
| expr.span, | ||||||
| receiver_snip.into_owned(), | ||||||
| applicability, | ||||||
| ); | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
| } | ||||||
|
|
||||||
| fn emit_lint(cx: &LateContext<'_, '_>, lint_span: Span, sugg_span: Span, sugg: String, applicability: Applicability) { | ||||||
| span_lint_and_then( | ||||||
| cx, | ||||||
| UNNEEDED_TRY_CONVERT, | ||||||
| lint_span, | ||||||
| "unneeded conversion inside `?`", | ||||||
| move |db| { | ||||||
| db.note("the `?` operator will automatically call `from` in the `Err` case"); | ||||||
| db.span_suggestion(sugg_span, "remove the conversion", sugg, applicability); | ||||||
| }, | ||||||
| ); | ||||||
| } | ||||||
|
|
||||||
| /// If `closure_expr` is a closure whose body is a conversion to `fn_error_ty`, | ||||||
| /// return (the span of the conversion call, the argument of the conversion call) | ||||||
| fn check_closure_expr<'tcx>( | ||||||
| cx: &LateContext<'_, 'tcx>, | ||||||
| fn_error_ty: Ty<'tcx>, | ||||||
| closure_expr: &Expr, | ||||||
| ) -> Option<(Span, &'tcx Expr)> { | ||||||
| if_chain! { | ||||||
| if let ExprKind::Closure(_, _, body_id, _, _) = closure_expr.kind; | ||||||
| let closure_body = &cx.tcx.hir().body(body_id).value; | ||||||
| if let Some(conv_arg) = conversion_subject(cx, closure_body); | ||||||
| if cx.tables.expr_ty(closure_body) == fn_error_ty; | ||||||
| then { | ||||||
| return Some((closure_body.span, conv_arg)); | ||||||
| } | ||||||
| } | ||||||
| None | ||||||
| } | ||||||
|
|
||||||
| /// If `expr` is `From::from(<inner>)` or `(<inner>).into()`, returns `<inner>`. | ||||||
| fn conversion_subject<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &'tcx Expr) -> Option<&'tcx Expr> { | ||||||
| if_chain! { | ||||||
| if let ExprKind::Call(fn_expr, from_args) = &expr.kind; | ||||||
| if let ExprKind::Path(fn_qpath) = &fn_expr.kind; | ||||||
| if let def::Res::Def(def::DefKind::Method, fn_did) = cx.tables.qpath_res(fn_qpath, fn_expr.hir_id); | ||||||
| if match_def_path(cx, fn_did, &paths::FROM_FROM); | ||||||
| if let [from_arg] = &**from_args; | ||||||
| then { | ||||||
| return Some(from_arg); | ||||||
| } | ||||||
| } | ||||||
| if_chain! { | ||||||
| if let ExprKind::MethodCall(_, _, args) = &expr.kind; | ||||||
| if let Some(call_did) = cx.tables.type_dependent_def_id(expr.hir_id); | ||||||
| if match_def_path(cx, call_did, &paths::INTO_INTO); | ||||||
| if let [receiver] = &**args; | ||||||
| then { | ||||||
| return Some(receiver); | ||||||
| } | ||||||
| } | ||||||
| None | ||||||
| } | ||||||
|
|
||||||
| /// Is this expression "trivial" such that a closure containing it could be inlined? | ||||||
| /// (currently very conservative) | ||||||
| fn is_trivial_expr<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &'tcx Expr) -> bool { | ||||||
| struct TrivialVisitor<'a, 'tcx> { | ||||||
| cx: &'a LateContext<'a, 'tcx>, | ||||||
| trivial: bool, | ||||||
| } | ||||||
|
|
||||||
| impl<'a, 'tcx> intravisit::Visitor<'tcx> for TrivialVisitor<'a, 'tcx> { | ||||||
| fn visit_expr(&mut self, expr: &'tcx hir::Expr) { | ||||||
| // whitelist of definitely trivial expressions | ||||||
| self.trivial &= match &expr.kind { | ||||||
| hir::ExprKind::Call(..) => is_ctor_or_promotable_const_function(self.cx, expr), | ||||||
| hir::ExprKind::Tup(..) | ||||||
| | hir::ExprKind::Lit(..) | ||||||
| | hir::ExprKind::Cast(..) | ||||||
| | hir::ExprKind::Field(..) | ||||||
| | hir::ExprKind::Index(..) | ||||||
| | hir::ExprKind::Path(..) | ||||||
| | hir::ExprKind::AddrOf(..) | ||||||
| | hir::ExprKind::Struct(..) => true, | ||||||
| _ => false, | ||||||
| }; | ||||||
|
|
||||||
| if self.trivial { | ||||||
| intravisit::walk_expr(self, expr); | ||||||
| } | ||||||
| } | ||||||
|
|
||||||
| fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> { | ||||||
| intravisit::NestedVisitorMap::None | ||||||
| } | ||||||
| } | ||||||
|
|
||||||
| let mut visitor = TrivialVisitor { cx, trivial: true }; | ||||||
| visitor.visit_expr(expr); | ||||||
| visitor.trivial | ||||||
| } | ||||||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,63 @@ | ||
| // run-rustfix | ||
| #![deny(clippy::unneeded_try_convert)] | ||
| #![allow(dead_code, unused_imports, clippy::redundant_closure)] | ||
|
|
||
| use std::convert::Into; | ||
|
|
||
| fn result_string() -> Result<(), String> { | ||
| let option = Some(3); | ||
| option.ok_or("foo")?; | ||
| option.ok_or_else(|| complex_computation())?; | ||
| // type arg not fixed | ||
| // option.ok_or_else::<String, _>(|| From::from(complex_computation()))?; | ||
| // type arg not fixed | ||
| // option.ok_or_else::<String, _>(|| "foo".into())?; | ||
|
|
||
| let result: Result<_, &'static str> = Ok(3); | ||
| result.map_err(|_| "foo")?; | ||
| result.map_err(|_| complex_computation())?; | ||
| // type arg not fixed | ||
| // result.map_err::<String, _>(|_| "foo".into())?; | ||
| result.map_err(|x| x)?; | ||
| result.map_err(|x| x.trim())?; | ||
| result?; | ||
| result?; | ||
| result?; | ||
|
|
||
| Ok(()) | ||
| } | ||
|
|
||
| fn in_closure() { | ||
| let option = Some(3); | ||
| let _ = || -> Result<_, String> { Ok(option.ok_or("foo")?) }; | ||
| } | ||
|
|
||
| #[allow(clippy::option_option)] | ||
| fn trivial_closure() { | ||
| let option = Some(3); | ||
| let _ = || -> Result<_, i32> { Ok(option.ok_or(0_u8)?) }; | ||
| let x: u8 = 0; | ||
| let _ = || -> Result<_, i32> { Ok(option.ok_or(x)?) }; | ||
| const X: u8 = 0; | ||
| let _ = || -> Result<_, i32> { Ok(option.ok_or(X)?) }; | ||
| let _ = | ||
| || -> Result<_, Option<Option<i32>>> { Ok(option.ok_or(Some(x as i32))?) }; | ||
| } | ||
|
|
||
| fn result_opt_string() -> Result<(), Option<String>> { | ||
| // can't convert &str -> Option<String> in one step | ||
| let option = Some(3); | ||
| option.ok_or_else(|| String::from("foo"))?; | ||
|
|
||
| let result: Result<_, &'static str> = Ok(3); | ||
| result.map_err(|_| String::from("foo"))?; | ||
| result.map_err(String::from)?; | ||
|
|
||
| Ok(()) | ||
| } | ||
|
|
||
| fn complex_computation() -> &'static str { | ||
| "bar" | ||
| } | ||
|
|
||
| fn main() {} |
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