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Auto merge of #6070 - matsujika:unnecessary_wrap, r=flip1995
Add new lint `unnecessary_wrap` Fixes #5969 changelog: New lint [`unnecessary_wraps`]
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,143 @@ | ||
| use crate::utils::{ | ||
| in_macro, is_type_diagnostic_item, match_qpath, paths, return_ty, snippet, span_lint_and_then, | ||
| visitors::find_all_ret_expressions, | ||
| }; | ||
| use if_chain::if_chain; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::intravisit::FnKind; | ||
| use rustc_hir::{Body, ExprKind, FnDecl, HirId, ItemKind, Node}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_middle::ty::subst::GenericArgKind; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
| 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:** Since this lint changes function type signature, you may need to | ||
| /// adjust some code at callee side. | ||
| /// | ||
| /// **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 | ||
| /// } | ||
| /// } | ||
| /// ``` | ||
| pub UNNECESSARY_WRAPS, | ||
| complexity, | ||
| "functions that only return `Ok` or `Some`" | ||
| } | ||
|
|
||
| declare_lint_pass!(UnnecessaryWraps => [UNNECESSARY_WRAPS]); | ||
|
|
||
| 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, | ||
| ) { | ||
| match fn_kind { | ||
| FnKind::ItemFn(.., visibility, _) | FnKind::Method(.., Some(visibility), _) => { | ||
| if visibility.node.is_pub() { | ||
| return; | ||
| } | ||
| }, | ||
| FnKind::Closure(..) => return, | ||
| _ => (), | ||
| } | ||
|
|
||
| if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_node(hir_id)) { | ||
| if matches!(item.kind, ItemKind::Impl{ of_trait: Some(_), ..} | ItemKind::Trait(..)) { | ||
| return; | ||
| } | ||
| } | ||
|
|
||
| let (return_type, path) = if is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym!(option_type)) { | ||
| ("Option", &paths::OPTION_SOME) | ||
| } else if is_type_diagnostic_item(cx, return_ty(cx, hir_id), sym!(result_type)) { | ||
| ("Result", &paths::RESULT_OK) | ||
| } else { | ||
| return; | ||
| }; | ||
|
|
||
| let mut suggs = Vec::new(); | ||
| let can_sugg = find_all_ret_expressions(cx, &body.value, |ret_expr| { | ||
| if_chain! { | ||
| if !in_macro(ret_expr.span); | ||
| if let ExprKind::Call(ref func, ref args) = ret_expr.kind; | ||
| if let ExprKind::Path(ref qpath) = func.kind; | ||
| if match_qpath(qpath, path); | ||
| if args.len() == 1; | ||
| then { | ||
| suggs.push((ret_expr.span, snippet(cx, args[0].span.source_callsite(), "..").to_string())); | ||
| true | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
| }); | ||
|
|
||
| if can_sugg && !suggs.is_empty() { | ||
| span_lint_and_then( | ||
| cx, | ||
| UNNECESSARY_WRAPS, | ||
| span, | ||
| format!( | ||
| "this function's return value is unnecessarily wrapped by `{}`", | ||
| return_type | ||
| ) | ||
| .as_str(), | ||
| |diag| { | ||
| let inner_ty = return_ty(cx, hir_id) | ||
| .walk() | ||
| .skip(1) // skip `std::option::Option` or `std::result::Result` | ||
| .take(1) // take the first outermost inner type | ||
| .filter_map(|inner| match inner.unpack() { | ||
| GenericArgKind::Type(inner_ty) => Some(inner_ty.to_string()), | ||
| _ => None, | ||
| }); | ||
| inner_ty.for_each(|inner_ty| { | ||
| diag.span_suggestion( | ||
| fn_decl.output.span(), | ||
| format!("remove `{}` from the return type...", return_type).as_str(), | ||
| inner_ty, | ||
| Applicability::MaybeIncorrect, | ||
| ); | ||
| }); | ||
| diag.multipart_suggestion( | ||
| "...and change the returning expressions", | ||
| suggs, | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
| } |
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