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Auto merge of #11413 - jonboh:master, r=Alexendoo
new unnecessary_map_on_constructor lint changelog: [`unnecessary_map_on_constructor`]: adds lint for cases in which map is not necessary. `Some(4).map(myfunction)` => `Some(myfunction(4))` Closes #6472 Note that the case mentioned in the issue `Some(..).and_then(|..| Some(..))` is fixed by a chain of lint changes. This PR completes the last part of that chain. By `bind_instead_of_map`[lint](https://rust-lang.github.io/rust-clippy/master/index.html#/bind_instead_of_map): `Some(4).and_then(|x| Some(foo(4)))` => `Some(4).map(|x| foo)` By `redundant_closure` [lint](https://rust-lang.github.io/rust-clippy/master/index.html#/redundant_closure): `Some(4).map(|x| foo)` => `Some(4).map(fun)` Finally by this PR `unnecessary_map_on_constructor`: `Some(4).map(fun)` => `Some(fun(4))` I'm not sure this is the desired behavior for clippy and if it should be addressed in another issue/PR. I'd be up to give it a try if that's the case.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,93 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_sugg; | ||
| use clippy_utils::source::snippet_with_applicability; | ||
| use clippy_utils::ty::get_type_diagnostic_name; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir as hir; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
| use rustc_span::sym; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Suggest removing the use of a may (or map_err) method when an Option or Result is being construted. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// It introduces unnecessary complexity. In this case the function can be used directly and | ||
| /// construct the Option or Result from the output. | ||
| /// | ||
| /// ### Example | ||
| /// ```rust | ||
| /// Some(4).map(i32::swap_bytes); | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust | ||
| /// Some(i32::swap_bytes(4)); | ||
| /// ``` | ||
| #[clippy::version = "1.73.0"] | ||
| pub UNNECESSARY_MAP_ON_CONSTRUCTOR, | ||
| complexity, | ||
| "using `map`/`map_err` on `Option` or `Result` constructors" | ||
| } | ||
| declare_lint_pass!(UnnecessaryMapOnConstructor => [UNNECESSARY_MAP_ON_CONSTRUCTOR]); | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for UnnecessaryMapOnConstructor { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx rustc_hir::Expr<'tcx>) { | ||
| if expr.span.from_expansion() { | ||
| return; | ||
| } | ||
| if let hir::ExprKind::MethodCall(path, recv, args, ..) = expr.kind | ||
| && let Some(sym::Option | sym::Result) = get_type_diagnostic_name(cx, cx.typeck_results().expr_ty(recv)){ | ||
| let (constructor_path, constructor_item) = | ||
| if let hir::ExprKind::Call(constructor, constructor_args) = recv.kind | ||
| && let hir::ExprKind::Path(constructor_path) = constructor.kind | ||
| && let Some(arg) = constructor_args.get(0) | ||
| { | ||
| if constructor.span.from_expansion() || arg.span.from_expansion() { | ||
| return; | ||
| } | ||
| (constructor_path, arg) | ||
| } else { | ||
| return; | ||
| }; | ||
| let constructor_symbol = match constructor_path { | ||
| hir::QPath::Resolved(_, path) => { | ||
| if let Some(path_segment) = path.segments.last() { | ||
| path_segment.ident.name | ||
| } else { | ||
| return; | ||
| } | ||
| }, | ||
| hir::QPath::TypeRelative(_, path) => path.ident.name, | ||
| hir::QPath::LangItem(_, _, _) => return, | ||
| }; | ||
| match constructor_symbol { | ||
| sym::Some | sym::Ok if path.ident.name == rustc_span::sym::map => (), | ||
| sym::Err if path.ident.name == sym!(map_err) => (), | ||
| _ => return, | ||
| } | ||
|
|
||
| if let Some(map_arg) = args.get(0) | ||
| && let hir::ExprKind::Path(fun) = map_arg.kind | ||
| { | ||
| if map_arg.span.from_expansion() { | ||
| return; | ||
| } | ||
| let mut applicability = Applicability::MachineApplicable; | ||
| let fun_snippet = snippet_with_applicability(cx, fun.span(), "_", &mut applicability); | ||
| let constructor_snippet = | ||
| snippet_with_applicability(cx, constructor_path.span(), "_", &mut applicability); | ||
| let constructor_arg_snippet = | ||
| snippet_with_applicability(cx, constructor_item.span, "_", &mut applicability); | ||
| span_lint_and_sugg( | ||
| cx, | ||
| UNNECESSARY_MAP_ON_CONSTRUCTOR, | ||
| expr.span, | ||
| &format!("unnecessary {} on constructor {constructor_snippet}(_)", path.ident.name), | ||
| "try", | ||
| format!("{constructor_snippet}({fun_snippet}({constructor_arg_snippet}))"), | ||
| applicability, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } |
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