use rustc::hir; use rustc::lint::*; use rustc::middle::const_val::ConstVal; use rustc::middle::const_qualif::ConstQualif; use rustc::ty; use rustc::hir::def::Def; use rustc_const_eval::EvalHint::ExprTypeChecked; use rustc_const_eval::eval_const_expr_partial; use std::borrow::Cow; use std::fmt; use syntax::codemap::Span; use utils::{get_trait_def_id, implements_trait, in_external_macro, in_macro, is_copy, match_path, match_trait_method, match_type, method_chain_args, return_ty, same_tys, snippet, span_lint, span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth, last_path_segment, single_segment_path, match_def_path}; use utils::paths; use utils::sugg; #[derive(Clone)] pub struct Pass; /// **What it does:** Checks for `.unwrap()` calls on `Option`s. /// /// **Why is this bad?** Usually it is better to handle the `None` case, or to /// at least call `.expect(_)` with a more helpful message. Still, for a lot of /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is /// `Allow` by default. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// x.unwrap() /// ``` declare_lint! { pub OPTION_UNWRAP_USED, Allow, "using `Option.unwrap()`, which should at least get a better message using `expect()`" } /// **What it does:** Checks for `.unwrap()` calls on `Result`s. /// /// **Why is this bad?** `result.unwrap()` will let the thread panic on `Err` /// values. Normally, you want to implement more sophisticated error handling, /// and propagate errors upwards with `try!`. /// /// Even if you want to panic on errors, not all `Error`s implement good /// messages on display. Therefore it may be beneficial to look at the places /// where they may get displayed. Activate this lint to do just that. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// x.unwrap() /// ``` declare_lint! { pub RESULT_UNWRAP_USED, Allow, "using `Result.unwrap()`, which might be better handled" } /// **What it does:** Checks for methods that should live in a trait /// implementation of a `std` trait (see [llogiq's blog /// post](http://llogiq.github.io/2015/07/30/traits.html) for further /// information) instead of an inherent implementation. /// /// **Why is this bad?** Implementing the traits improve ergonomics for users of /// the code, often with very little cost. Also people seeing a `mul(...)` method /// may expect `*` to work equally, so you should have good reason to disappoint /// them. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// struct X; /// impl X { /// fn add(&self, other: &X) -> X { .. } /// } /// ``` declare_lint! { pub SHOULD_IMPLEMENT_TRAIT, Warn, "defining a method that should be implementing a std trait" } /// **What it does:** Checks for methods with certain name prefixes and which /// doesn't match how self is taken. The actual rules are: /// /// |Prefix |`self` taken | /// |-------|----------------------| /// |`as_` |`&self` or `&mut self`| /// |`from_`| none | /// |`into_`|`self` | /// |`is_` |`&self` or none | /// |`to_` |`&self` | /// /// **Why is this bad?** Consistency breeds readability. If you follow the /// conventions, your users won't be surprised that they, e.g., need to supply a /// mutable reference to a `as_..` function. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// impl X { /// fn as_str(self) -> &str { .. } /// } /// ``` declare_lint! { pub WRONG_SELF_CONVENTION, Warn, "defining a method named with an established prefix (like \"into_\") that takes \ `self` with the wrong convention" } /// **What it does:** This is the same as /// [`wrong_self_convention`](#wrong_self_convention), but for public items. /// /// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention). /// /// **Known problems:** Actually *renaming* the function may break clients if /// the function is part of the public interface. In that case, be mindful of /// the stability guarantees you've given your users. /// /// **Example:** /// ```rust /// impl X { /// pub fn as_str(self) -> &str { .. } /// } /// ``` declare_lint! { pub WRONG_PUB_SELF_CONVENTION, Allow, "defining a public method named with an established prefix (like \"into_\") that takes \ `self` with the wrong convention" } /// **What it does:** Checks for usage of `ok().expect(..)`. /// /// **Why is this bad?** Because you usually call `expect()` on the `Result` /// directly to get a better error message. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// x.ok().expect("why did I do this again?") /// ``` declare_lint! { pub OK_EXPECT, Warn, "using `ok().expect()`, which gives worse error messages than \ calling `expect` directly on the Result" } /// **What it does:** Checks for usage of `_.map(_).unwrap_or(_)`. /// /// **Why is this bad?** Readability, this can be written more concisely as /// `_.map_or(_, _)`. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// x.map(|a| a + 1).unwrap_or(0) /// ``` declare_lint! { pub OPTION_MAP_UNWRAP_OR, Allow, "using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \ `map_or(a, f)`" } /// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`. /// /// **Why is this bad?** Readability, this can be written more concisely as /// `_.map_or_else(_, _)`. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// x.map(|a| a + 1).unwrap_or_else(some_function) /// ``` declare_lint! { pub OPTION_MAP_UNWRAP_OR_ELSE, Allow, "using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \ `map_or_else(g, f)`" } /// **What it does:** Checks for usage of `_.filter(_).next()`. /// /// **Why is this bad?** Readability, this can be written more concisely as /// `_.find(_)`. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// iter.filter(|x| x == 0).next() /// ``` declare_lint! { pub FILTER_NEXT, Warn, "using `filter(p).next()`, which is more succinctly expressed as `.find(p)`" } /// **What it does:** Checks for usage of `_.filter(_).map(_)`, /// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar. /// /// **Why is this bad?** Readability, this can be written more concisely as a /// single method call. /// /// **Known problems:** Often requires a condition + Option/Iterator creation /// inside the closure. /// /// **Example:** /// ```rust /// iter.filter(|x| x == 0).map(|x| x * 2) /// ``` declare_lint! { pub FILTER_MAP, Allow, "using combinations of `filter`, `map`, `filter_map` and `flat_map` which can \ usually be written as a single method call" } /// **What it does:** Checks for an iterator search (such as `find()`, /// `position()`, or `rposition()`) followed by a call to `is_some()`. /// /// **Why is this bad?** Readability, this can be written more concisely as /// `_.any(_)`. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// iter.find(|x| x == 0).is_some() /// ``` declare_lint! { pub SEARCH_IS_SOME, Warn, "using an iterator search followed by `is_some()`, which is more succinctly \ expressed as a call to `any()`" } /// **What it does:** Checks for usage of `.chars().next()` on a `str` to check /// if it starts with a given char. /// /// **Why is this bad?** Readability, this can be written more concisely as /// `_.starts_with(_)`. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// name.chars().next() == Some('_') /// ``` declare_lint! { pub CHARS_NEXT_CMP, Warn, "using `.chars().next()` to check if a string starts with a char" } /// **What it does:** Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`, /// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or /// `unwrap_or_default` instead. /// /// **Why is this bad?** The function will always be called and potentially /// allocate an object acting as the default. /// /// **Known problems:** If the function has side-effects, not calling it will /// change the semantic of the program, but you shouldn't rely on that anyway. /// /// **Example:** /// ```rust /// foo.unwrap_or(String::new()) /// ``` /// this can instead be written: /// ```rust /// foo.unwrap_or_else(String::new) /// ``` /// or /// ```rust /// foo.unwrap_or_default() /// ``` declare_lint! { pub OR_FUN_CALL, Warn, "using any `*or` method with a function call, which suggests `*or_else`" } /// **What it does:** Checks for usage of `.extend(s)` on a `Vec` to extend the /// vector by a slice. /// /// **Why is this bad?** Since Rust 1.6, the `extend_from_slice(_)` method is /// stable and at least for now faster. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// my_vec.extend(&xs) /// ``` declare_lint! { pub EXTEND_FROM_SLICE, Warn, "`.extend_from_slice(_)` is a faster way to extend a Vec by a slice" } /// **What it does:** Checks for usage of `.clone()` on a `Copy` type. /// /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for /// generics, not for using the `clone` method on a concrete type. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// 42u64.clone() /// ``` declare_lint! { pub CLONE_ON_COPY, Warn, "using `clone` on a `Copy` type" } /// **What it does:** Checks for usage of `.clone()` on an `&&T`. /// /// **Why is this bad?** Cloning an `&&T` copies the inner `&T`, instead of /// cloning the underlying `T`. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// fn main() { /// let x = vec![1]; /// let y = &&x; /// let z = y.clone(); /// println!("{:p} {:p}",*y, z); // prints out the same pointer /// } /// ``` declare_lint! { pub CLONE_DOUBLE_REF, Warn, "using `clone` on `&&T`" } /// **What it does:** Checks for `new` not returning `Self`. /// /// **Why is this bad?** As a convention, `new` methods are used to make a new /// instance of a type. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// impl Foo { /// fn new(..) -> NotAFoo { /// } /// } /// ``` declare_lint! { pub NEW_RET_NO_SELF, Warn, "not returning `Self` in a `new` method" } /// **What it does:** Checks for string methods that receive a single-character /// `str` as an argument, e.g. `_.split("x")`. /// /// **Why is this bad?** Performing these methods using a `char` is faster than /// using a `str`. /// /// **Known problems:** Does not catch multi-byte unicode characters. /// /// **Example:** /// `_.split("x")` could be `_.split('x') declare_lint! { pub SINGLE_CHAR_PATTERN, Warn, "using a single-character str where a char could be used, e.g. \ `_.split(\"x\")`" } /// **What it does:** Checks for getting the inner pointer of a temporary `CString`. /// /// **Why is this bad?** The inner pointer of a `CString` is only valid as long /// as the `CString` is alive. /// /// **Known problems:** None. /// /// **Example:** /// ```rust,ignore /// let c_str = CString::new("foo").unwrap().as_ptr(); /// unsafe { /// call_some_ffi_func(c_str); /// } /// ``` /// Here `c_str` point to a freed address. The correct use would be: /// ```rust,ignore /// let c_str = CString::new("foo").unwrap(); /// unsafe { /// call_some_ffi_func(c_str.as_ptr()); /// } /// ``` declare_lint! { pub TEMPORARY_CSTRING_AS_PTR, Warn, "getting the inner pointer of a temporary `CString`" } /// **What it does:** Checks for use of `.iter().nth()` (and the related /// `.iter_mut().nth()`) on standard library types with O(1) element access. /// /// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more /// readable. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let some_vec = vec![0, 1, 2, 3]; /// let bad_vec = some_vec.iter().nth(3); /// let bad_slice = &some_vec[..].iter().nth(3); /// ``` /// The correct use would be: /// ```rust /// let some_vec = vec![0, 1, 2, 3]; /// let bad_vec = some_vec.get(3); /// let bad_slice = &some_vec[..].get(3); /// ``` declare_lint! { pub ITER_NTH, Warn, "using `.iter().nth()` on a standard library type with O(1) element access" } /// **What it does:** Checks for use of `.skip(x).next()` on iterators. /// /// **Why is this bad?** `.nth(x)` is cleaner /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let some_vec = vec![0, 1, 2, 3]; /// let bad_vec = some_vec.iter().skip(3).next(); /// let bad_slice = &some_vec[..].iter().skip(3).next(); /// ``` /// The correct use would be: /// ```rust /// let some_vec = vec![0, 1, 2, 3]; /// let bad_vec = some_vec.iter().nth(3); /// let bad_slice = &some_vec[..].iter().nth(3); /// ``` declare_lint! { pub ITER_SKIP_NEXT, Warn, "using `.skip(x).next()` on an iterator" } /// **What it does:** Checks for use of `.get().unwrap()` (or /// `.get_mut().unwrap`) on a standard library type which implements `Index` /// /// **Why is this bad?** Using the Index trait (`[]`) is more clear and more /// concise. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let some_vec = vec![0, 1, 2, 3]; /// let last = some_vec.get(3).unwrap(); /// *some_vec.get_mut(0).unwrap() = 1; /// ``` /// The correct use would be: /// ```rust /// let some_vec = vec![0, 1, 2, 3]; /// let last = some_vec[3]; /// some_vec[0] = 1; /// ``` declare_lint! { pub GET_UNWRAP, Warn, "using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead" } /// **What it does:** Checks for the use of `.extend(s.chars())` where s is a /// `&str` or `String`. /// /// **Why is this bad?** `.push_str(s)` is clearer /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// let abc = "abc"; /// let def = String::from("def"); /// let mut s = String::new(); /// s.extend(abc.chars()); /// s.extend(def.chars()); /// ``` /// The correct use would be: /// ```rust /// let abc = "abc"; /// let def = String::from("def"); /// let mut s = String::new(); /// s.push_str(abc); /// s.push_str(&def)); /// ``` declare_lint! { pub STRING_EXTEND_CHARS, Warn, "using `x.extend(s.chars())` where s is a `&str` or `String`" } impl LintPass for Pass { fn get_lints(&self) -> LintArray { lint_array!(EXTEND_FROM_SLICE, OPTION_UNWRAP_USED, RESULT_UNWRAP_USED, SHOULD_IMPLEMENT_TRAIT, WRONG_SELF_CONVENTION, WRONG_PUB_SELF_CONVENTION, OK_EXPECT, OPTION_MAP_UNWRAP_OR, OPTION_MAP_UNWRAP_OR_ELSE, OR_FUN_CALL, CHARS_NEXT_CMP, CLONE_ON_COPY, CLONE_DOUBLE_REF, NEW_RET_NO_SELF, SINGLE_CHAR_PATTERN, SEARCH_IS_SOME, TEMPORARY_CSTRING_AS_PTR, FILTER_NEXT, FILTER_MAP, ITER_NTH, ITER_SKIP_NEXT, GET_UNWRAP, STRING_EXTEND_CHARS) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { #[allow(unused_attributes)] // ^ required because `cyclomatic_complexity` attribute shows up as unused #[cyclomatic_complexity = "30"] fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) { if in_macro(cx, expr.span) { return; } match expr.node { hir::ExprMethodCall(name, _, ref args) => { // Chain calls // GET_UNWRAP needs to be checked before general `UNWRAP` lints if let Some(arglists) = method_chain_args(expr, &["get", "unwrap"]) { lint_get_unwrap(cx, expr, arglists[0], false); } else if let Some(arglists) = method_chain_args(expr, &["get_mut", "unwrap"]) { lint_get_unwrap(cx, expr, arglists[0], true); } else if let Some(arglists) = method_chain_args(expr, &["unwrap"]) { lint_unwrap(cx, expr, arglists[0]); } else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) { lint_ok_expect(cx, expr, arglists[0]); } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) { lint_map_unwrap_or(cx, expr, arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) { lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) { lint_filter_next(cx, expr, arglists[0]); } else if let Some(arglists) = method_chain_args(expr, &["filter", "map"]) { lint_filter_map(cx, expr, arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["filter_map", "map"]) { lint_filter_map_map(cx, expr, arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["filter", "flat_map"]) { lint_filter_flat_map(cx, expr, arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["filter_map", "flat_map"]) { lint_filter_map_flat_map(cx, expr, arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) { lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) { lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) { lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]); } else if let Some(arglists) = method_chain_args(expr, &["extend"]) { lint_extend(cx, expr, arglists[0]); } else if let Some(arglists) = method_chain_args(expr, &["unwrap", "as_ptr"]) { lint_cstring_as_ptr(cx, expr, &arglists[0][0], &arglists[1][0]); } else if let Some(arglists) = method_chain_args(expr, &["iter", "nth"]) { lint_iter_nth(cx, expr, arglists[0], false); } else if let Some(arglists) = method_chain_args(expr, &["iter_mut", "nth"]) { lint_iter_nth(cx, expr, arglists[0], true); } else if method_chain_args(expr, &["skip", "next"]).is_some() { lint_iter_skip_next(cx, expr); } lint_or_fun_call(cx, expr, &name.node.as_str(), args); let self_ty = cx.tcx.tables().expr_ty_adjusted(&args[0]); if args.len() == 1 && &*name.node.as_str() == "clone" { lint_clone_on_copy(cx, expr, &args[0], self_ty); } match self_ty.sty { ty::TyRef(_, ty) if ty.ty.sty == ty::TyStr => { for &(method, pos) in &PATTERN_METHODS { if &*name.node.as_str() == method && args.len() > pos { lint_single_char_pattern(cx, expr, &args[pos]); } } }, _ => (), } }, hir::ExprBinary(op, ref lhs, ref rhs) if op.node == hir::BiEq || op.node == hir::BiNe => { if !lint_chars_next(cx, expr, lhs, rhs, op.node == hir::BiEq) { lint_chars_next(cx, expr, rhs, lhs, op.node == hir::BiEq); } }, _ => (), } } fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, implitem: &'tcx hir::ImplItem) { if in_external_macro(cx, implitem.span) { return; } let name = implitem.name; let parent = cx.tcx.map.get_parent(implitem.id); let item = cx.tcx.map.expect_item(parent); if_let_chain! {[ let hir::ImplItemKind::Method(ref sig, _) = implitem.node, let Some(explicit_self) = sig.decl.inputs.get(0).and_then(hir::Arg::to_self), let hir::ItemImpl(_, _, _, None, _, _) = item.node, ], { // check missing trait implementations for &(method_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS { if &*name.as_str() == method_name && sig.decl.inputs.len() == n_args && out_type.matches(&sig.decl.output) && self_kind.matches(&explicit_self, false) { span_lint(cx, SHOULD_IMPLEMENT_TRAIT, implitem.span, &format!( "defining a method called `{}` on this type; consider implementing \ the `{}` trait or choosing a less ambiguous name", name, trait_name)); } } // check conventions w.r.t. conversion method names and predicates let ty = cx.tcx.item_type(cx.tcx.map.local_def_id(item.id)); let is_copy = is_copy(cx, ty, item.id); for &(ref conv, self_kinds) in &CONVENTIONS { if_let_chain! {[ conv.check(&name.as_str()), let Some(explicit_self) = sig.decl.inputs.get(0).and_then(hir::Arg::to_self), !self_kinds.iter().any(|k| k.matches(&explicit_self, is_copy)), ], { let lint = if item.vis == hir::Visibility::Public { WRONG_PUB_SELF_CONVENTION } else { WRONG_SELF_CONVENTION }; span_lint(cx, lint, explicit_self.span, &format!("methods called `{}` usually take {}; consider choosing a less \ ambiguous name", conv, &self_kinds.iter() .map(|k| k.description()) .collect::>() .join(" or "))); }} } let ret_ty = return_ty(cx, implitem.id); if &*name.as_str() == "new" && !ret_ty.walk().any(|t| same_tys(cx, t, ty, implitem.id)) { span_lint(cx, NEW_RET_NO_SELF, explicit_self.span, "methods called `new` usually return `Self`"); } }} } } /// Checks for the `OR_FUN_CALL` lint. fn lint_or_fun_call(cx: &LateContext, expr: &hir::Expr, name: &str, args: &[hir::Expr]) { /// Check for `unwrap_or(T::new())` or `unwrap_or(T::default())`. fn check_unwrap_or_default(cx: &LateContext, name: &str, fun: &hir::Expr, self_expr: &hir::Expr, arg: &hir::Expr, or_has_args: bool, span: Span) -> bool { if or_has_args { return false; } if name == "unwrap_or" { if let hir::ExprPath(ref qpath) = fun.node { let path: &str = &*last_path_segment(qpath).name.as_str(); if ["default", "new"].contains(&path) { let arg_ty = cx.tcx.tables().expr_ty(arg); let default_trait_id = if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT) { default_trait_id } else { return false; }; if implements_trait(cx, arg_ty, default_trait_id, Vec::new()) { span_lint_and_then(cx, OR_FUN_CALL, span, &format!("use of `{}` followed by a call to `{}`", name, path), |db| { db.span_suggestion(span, "try this", format!("{}.unwrap_or_default()", snippet(cx, self_expr.span, "_"))); }); return true; } } } } false } /// Check for `*or(foo())`. fn check_general_case(cx: &LateContext, name: &str, fun: &hir::Expr, self_expr: &hir::Expr, arg: &hir::Expr, or_has_args: bool, span: Span) { // don't lint for constant values // FIXME: can we `expect` here instead of match? if let Some(qualif) = cx.tcx.const_qualif_map.borrow().get(&arg.id) { if !qualif.contains(ConstQualif::NOT_CONST) { return; } } // (path, fn_has_argument, methods, suffix) let know_types: &[(&[_], _, &[_], _)] = &[(&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"), (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"), (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"), (&paths::RESULT, true, &["or", "unwrap_or"], "else")]; let self_ty = cx.tcx.tables().expr_ty(self_expr); let (fn_has_arguments, poss, suffix) = if let Some(&(_, fn_has_arguments, poss, suffix)) = know_types.iter().find(|&&i| match_type(cx, self_ty, i.0)) { (fn_has_arguments, poss, suffix) } else { return; }; if !poss.contains(&name) { return; } let sugg: Cow<_> = match (fn_has_arguments, !or_has_args) { (true, _) => format!("|_| {}", snippet(cx, arg.span, "..")).into(), (false, false) => format!("|| {}", snippet(cx, arg.span, "..")).into(), (false, true) => snippet(cx, fun.span, ".."), }; span_lint_and_then(cx, OR_FUN_CALL, span, &format!("use of `{}` followed by a function call", name), |db| { db.span_suggestion(span, "try this", format!("{}.{}_{}({})", snippet(cx, self_expr.span, "_"), name, suffix, sugg)); }); } if args.len() == 2 { if let hir::ExprCall(ref fun, ref or_args) = args[1].node { let or_has_args = !or_args.is_empty(); if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) { check_general_case(cx, name, fun, &args[0], &args[1], or_has_args, expr.span); } } } } /// Checks for the `CLONE_ON_COPY` lint. fn lint_clone_on_copy(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr, arg_ty: ty::Ty) { let ty = cx.tcx.tables().expr_ty(expr); let parent = cx.tcx.map.get_parent(expr.id); let parameter_environment = ty::ParameterEnvironment::for_item(cx.tcx, parent); if let ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) = arg_ty.sty { if let ty::TyRef(..) = inner.sty { span_lint_and_then(cx, CLONE_DOUBLE_REF, expr.span, "using `clone` on a double-reference; \ this will copy the reference instead of cloning the inner type", |db| if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) { db.span_suggestion(expr.span, "try dereferencing it", format!("({}).clone()", snip.deref())); }); return; // don't report clone_on_copy } } if !ty.moves_by_default(cx.tcx.global_tcx(), ¶meter_environment, expr.span) { span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) { if let ty::TyRef(..) = cx.tcx.tables().expr_ty(arg).sty { db.span_suggestion(expr.span, "try dereferencing it", format!("{}", snip.deref())); } else { db.span_suggestion(expr.span, "try removing the `clone` call", format!("{}", snip)); } }); } } fn lint_vec_extend(cx: &LateContext, expr: &hir::Expr, args: &[hir::Expr]) { let arg_ty = cx.tcx.tables().expr_ty(&args[1]); if let Some(slice) = derefs_to_slice(cx, &args[1], arg_ty) { span_lint_and_then(cx, EXTEND_FROM_SLICE, expr.span, "use of `extend` to extend a Vec by a slice", |db| { db.span_suggestion(expr.span, "try this", format!("{}.extend_from_slice({})", snippet(cx, args[0].span, "_"), slice)); }); } } fn lint_string_extend(cx: &LateContext, expr: &hir::Expr, args: &[hir::Expr]) { let arg = &args[1]; if let Some(arglists) = method_chain_args(arg, &["chars"]) { let target = &arglists[0][0]; let (self_ty, _) = walk_ptrs_ty_depth(cx.tcx.tables().expr_ty(target)); let ref_str = if self_ty.sty == ty::TyStr { "" } else if match_type(cx, self_ty, &paths::STRING) { "&" } else { return; }; span_lint_and_then(cx, STRING_EXTEND_CHARS, expr.span, "calling `.extend(_.chars())`", |db| { db.span_suggestion(expr.span, "try this", format!("{}.push_str({}{})", snippet(cx, args[0].span, "_"), ref_str, snippet(cx, target.span, "_"))); }); } } fn lint_extend(cx: &LateContext, expr: &hir::Expr, args: &[hir::Expr]) { let (obj_ty, _) = walk_ptrs_ty_depth(cx.tcx.tables().expr_ty(&args[0])); if match_type(cx, obj_ty, &paths::VEC) { lint_vec_extend(cx, expr, args); } else if match_type(cx, obj_ty, &paths::STRING) { lint_string_extend(cx, expr, args); } } fn lint_cstring_as_ptr(cx: &LateContext, expr: &hir::Expr, new: &hir::Expr, unwrap: &hir::Expr) { if_let_chain!{[ let hir::ExprCall(ref fun, ref args) = new.node, args.len() == 1, let hir::ExprPath(ref path) = fun.node, let Def::Method(did) = cx.tcx.tables().qpath_def(path, fun.id), match_def_path(cx, did, &paths::CSTRING_NEW) ], { span_lint_and_then(cx, TEMPORARY_CSTRING_AS_PTR, expr.span, "you are getting the inner pointer of a temporary `CString`", |db| { db.note("that pointer will be invalid outside this expression"); db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime"); }); }} } fn lint_iter_nth(cx: &LateContext, expr: &hir::Expr, iter_args: &[hir::Expr], is_mut: bool) { let mut_str = if is_mut { "_mut" } else { "" }; let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tcx.tables().expr_ty(&iter_args[0])).is_some() { "slice" } else if match_type(cx, cx.tcx.tables().expr_ty(&iter_args[0]), &paths::VEC) { "Vec" } else if match_type(cx, cx.tcx.tables().expr_ty(&iter_args[0]), &paths::VEC_DEQUE) { "VecDeque" } else { return; // caller is not a type that we want to lint }; span_lint(cx, ITER_NTH, expr.span, &format!("called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable", mut_str, caller_type)); } fn lint_get_unwrap(cx: &LateContext, expr: &hir::Expr, get_args: &[hir::Expr], is_mut: bool) { // Note: we don't want to lint `get_mut().unwrap` for HashMap or BTreeMap, // because they do not implement `IndexMut` let expr_ty = cx.tcx.tables().expr_ty(&get_args[0]); let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() { "slice" } else if match_type(cx, expr_ty, &paths::VEC) { "Vec" } else if match_type(cx, expr_ty, &paths::VEC_DEQUE) { "VecDeque" } else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) { "HashMap" } else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) { "BTreeMap" } else { return; // caller is not a type that we want to lint }; let mut_str = if is_mut { "_mut" } else { "" }; let borrow_str = if is_mut { "&mut " } else { "&" }; span_lint_and_then(cx, GET_UNWRAP, expr.span, &format!("called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise", mut_str, caller_type), |db| { db.span_suggestion(expr.span, "try this", format!("{}{}[{}]", borrow_str, snippet(cx, get_args[0].span, "_"), snippet(cx, get_args[1].span, "_"))); }); } fn lint_iter_skip_next(cx: &LateContext, expr: &hir::Expr) { // lint if caller of skip is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { span_lint(cx, ITER_SKIP_NEXT, expr.span, "called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)`"); } } fn derefs_to_slice(cx: &LateContext, expr: &hir::Expr, ty: ty::Ty) -> Option> { fn may_slice(cx: &LateContext, ty: ty::Ty) -> bool { match ty.sty { ty::TySlice(_) => true, ty::TyAdt(..) => match_type(cx, ty, &paths::VEC), ty::TyArray(_, size) => size < 32, ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) | ty::TyBox(inner) => may_slice(cx, inner), _ => false, } } if let hir::ExprMethodCall(name, _, ref args) = expr.node { if &*name.node.as_str() == "iter" && may_slice(cx, cx.tcx.tables().expr_ty(&args[0])) { sugg::Sugg::hir_opt(cx, &args[0]).map(|sugg| sugg.addr()) } else { None } } else { match ty.sty { ty::TySlice(_) => sugg::Sugg::hir_opt(cx, expr), ty::TyRef(_, ty::TypeAndMut { ty: inner, .. }) | ty::TyBox(inner) => { if may_slice(cx, inner) { sugg::Sugg::hir_opt(cx, expr) } else { None } }, _ => None, } } } /// lint use of `unwrap()` for `Option`s and `Result`s fn lint_unwrap(cx: &LateContext, expr: &hir::Expr, unwrap_args: &[hir::Expr]) { let (obj_ty, _) = walk_ptrs_ty_depth(cx.tcx.tables().expr_ty(&unwrap_args[0])); let mess = if match_type(cx, obj_ty, &paths::OPTION) { Some((OPTION_UNWRAP_USED, "an Option", "None")) } else if match_type(cx, obj_ty, &paths::RESULT) { Some((RESULT_UNWRAP_USED, "a Result", "Err")) } else { None }; if let Some((lint, kind, none_value)) = mess { span_lint(cx, lint, expr.span, &format!("used unwrap() on {} value. If you don't want to handle the {} case gracefully, consider \ using expect() to provide a better panic message", kind, none_value)); } } /// lint use of `ok().expect()` for `Result`s fn lint_ok_expect(cx: &LateContext, expr: &hir::Expr, ok_args: &[hir::Expr]) { // lint if the caller of `ok()` is a `Result` if match_type(cx, cx.tcx.tables().expr_ty(&ok_args[0]), &paths::RESULT) { let result_type = cx.tcx.tables().expr_ty(&ok_args[0]); if let Some(error_type) = get_error_type(cx, result_type) { if has_debug_impl(error_type, cx) { span_lint(cx, OK_EXPECT, expr.span, "called `ok().expect()` on a Result value. You can call `expect` directly on the `Result`"); } } } } /// lint use of `map().unwrap_or()` for `Option`s fn lint_map_unwrap_or(cx: &LateContext, expr: &hir::Expr, map_args: &[hir::Expr], unwrap_args: &[hir::Expr]) { // lint if the caller of `map()` is an `Option` if match_type(cx, cx.tcx.tables().expr_ty(&map_args[0]), &paths::OPTION) { // lint message let msg = "called `map(f).unwrap_or(a)` on an Option value. This can be done more directly by calling \ `map_or(a, f)` instead"; // get snippets for args to map() and unwrap_or() let map_snippet = snippet(cx, map_args[1].span, ".."); let unwrap_snippet = snippet(cx, unwrap_args[1].span, ".."); // lint, with note if neither arg is > 1 line and both map() and // unwrap_or() have the same span let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1; let same_span = map_args[1].span.expn_id == unwrap_args[1].span.expn_id; if same_span && !multiline { span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span, &format!("replace `map({0}).unwrap_or({1})` with `map_or({1}, {0})`", map_snippet, unwrap_snippet)); } else if same_span && multiline { span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg); }; } } /// lint use of `map().unwrap_or_else()` for `Option`s fn lint_map_unwrap_or_else(cx: &LateContext, expr: &hir::Expr, map_args: &[hir::Expr], unwrap_args: &[hir::Expr]) { // lint if the caller of `map()` is an `Option` if match_type(cx, cx.tcx.tables().expr_ty(&map_args[0]), &paths::OPTION) { // lint message let msg = "called `map(f).unwrap_or_else(g)` on an Option value. This can be done more directly by calling \ `map_or_else(g, f)` instead"; // get snippets for args to map() and unwrap_or_else() let map_snippet = snippet(cx, map_args[1].span, ".."); let unwrap_snippet = snippet(cx, unwrap_args[1].span, ".."); // lint, with note if neither arg is > 1 line and both map() and // unwrap_or_else() have the same span let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1; let same_span = map_args[1].span.expn_id == unwrap_args[1].span.expn_id; if same_span && !multiline { span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg, expr.span, &format!("replace `map({0}).unwrap_or_else({1})` with `with map_or_else({1}, {0})`", map_snippet, unwrap_snippet)); } else if same_span && multiline { span_lint(cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg); }; } } /// lint use of `filter().next()` for `Iterators` fn lint_filter_next(cx: &LateContext, expr: &hir::Expr, filter_args: &[hir::Expr]) { // lint if caller of `.filter().next()` is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \ `.find(p)` instead."; let filter_snippet = snippet(cx, filter_args[1].span, ".."); if filter_snippet.lines().count() <= 1 { // add note if not multi-line span_note_and_lint(cx, FILTER_NEXT, expr.span, msg, expr.span, &format!("replace `filter({0}).next()` with `find({0})`", filter_snippet)); } else { span_lint(cx, FILTER_NEXT, expr.span, msg); } } } /// lint use of `filter().map()` for `Iterators` fn lint_filter_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &[hir::Expr], _map_args: &[hir::Expr]) { // lint if caller of `.filter().map()` is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { let msg = "called `filter(p).map(q)` on an `Iterator`. \ This is more succinctly expressed by calling `.filter_map(..)` instead."; span_lint(cx, FILTER_MAP, expr.span, msg); } } /// lint use of `filter().map()` for `Iterators` fn lint_filter_map_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &[hir::Expr], _map_args: &[hir::Expr]) { // lint if caller of `.filter().map()` is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { let msg = "called `filter_map(p).map(q)` on an `Iterator`. \ This is more succinctly expressed by only calling `.filter_map(..)` instead."; span_lint(cx, FILTER_MAP, expr.span, msg); } } /// lint use of `filter().flat_map()` for `Iterators` fn lint_filter_flat_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &[hir::Expr], _map_args: &[hir::Expr]) { // lint if caller of `.filter().flat_map()` is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { let msg = "called `filter(p).flat_map(q)` on an `Iterator`. \ This is more succinctly expressed by calling `.flat_map(..)` \ and filtering by returning an empty Iterator."; span_lint(cx, FILTER_MAP, expr.span, msg); } } /// lint use of `filter_map().flat_map()` for `Iterators` fn lint_filter_map_flat_map(cx: &LateContext, expr: &hir::Expr, _filter_args: &[hir::Expr], _map_args: &[hir::Expr]) { // lint if caller of `.filter_map().flat_map()` is an Iterator if match_trait_method(cx, expr, &paths::ITERATOR) { let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`. \ This is more succinctly expressed by calling `.flat_map(..)` \ and filtering by returning an empty Iterator."; span_lint(cx, FILTER_MAP, expr.span, msg); } } /// lint searching an Iterator followed by `is_some()` fn lint_search_is_some(cx: &LateContext, expr: &hir::Expr, search_method: &str, search_args: &[hir::Expr], is_some_args: &[hir::Expr]) { // lint if caller of search is an Iterator if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) { let msg = format!("called `is_some()` after searching an `Iterator` with {}. This is more succinctly \ expressed by calling `any()`.", search_method); let search_snippet = snippet(cx, search_args[1].span, ".."); if search_snippet.lines().count() <= 1 { // add note if not multi-line span_note_and_lint(cx, SEARCH_IS_SOME, expr.span, &msg, expr.span, &format!("replace `{0}({1}).is_some()` with `any({1})`", search_method, search_snippet)); } else { span_lint(cx, SEARCH_IS_SOME, expr.span, &msg); } } } /// Checks for the `CHARS_NEXT_CMP` lint. fn lint_chars_next(cx: &LateContext, expr: &hir::Expr, chain: &hir::Expr, other: &hir::Expr, eq: bool) -> bool { if_let_chain! {[ let Some(args) = method_chain_args(chain, &["chars", "next"]), let hir::ExprCall(ref fun, ref arg_char) = other.node, arg_char.len() == 1, let hir::ExprPath(ref qpath) = fun.node, let Some(segment) = single_segment_path(qpath), &*segment.name.as_str() == "Some" ], { let self_ty = walk_ptrs_ty(cx.tcx.tables().expr_ty_adjusted(&args[0][0])); if self_ty.sty != ty::TyStr { return false; } span_lint_and_then(cx, CHARS_NEXT_CMP, expr.span, "you should use the `starts_with` method", |db| { let sugg = format!("{}{}.starts_with({})", if eq { "" } else { "!" }, snippet(cx, args[0][0].span, "_"), snippet(cx, arg_char[0].span, "_") ); db.span_suggestion(expr.span, "like this", sugg); }); return true; }} false } /// lint for length-1 `str`s for methods in `PATTERN_METHODS` fn lint_single_char_pattern(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr) { if let Ok(ConstVal::Str(r)) = eval_const_expr_partial(cx.tcx, arg, ExprTypeChecked, None) { if r.len() == 1 { let hint = snippet(cx, expr.span, "..").replace(&format!("\"{}\"", r), &format!("'{}'", r)); span_lint_and_then(cx, SINGLE_CHAR_PATTERN, arg.span, "single-character string constant used as pattern", |db| { db.span_suggestion(expr.span, "try using a char instead:", hint); }); } } } /// Given a `Result` type, return its error type (`E`). fn get_error_type<'a>(cx: &LateContext, ty: ty::Ty<'a>) -> Option> { if let ty::TyAdt(_, substs) = ty.sty { if match_type(cx, ty, &paths::RESULT) { substs.types().nth(1) } else { None } } else { None } } /// This checks whether a given type is known to implement Debug. fn has_debug_impl<'a, 'b>(ty: ty::Ty<'a>, cx: &LateContext<'b, 'a>) -> bool { match cx.tcx.lang_items.debug_trait() { Some(debug) => implements_trait(cx, ty, debug, Vec::new()), None => false, } } enum Convention { Eq(&'static str), StartsWith(&'static str), } #[cfg_attr(rustfmt, rustfmt_skip)] const CONVENTIONS: [(Convention, &'static [SelfKind]); 6] = [ (Convention::Eq("new"), &[SelfKind::No]), (Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]), (Convention::StartsWith("from_"), &[SelfKind::No]), (Convention::StartsWith("into_"), &[SelfKind::Value]), (Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]), (Convention::StartsWith("to_"), &[SelfKind::Ref]), ]; #[cfg_attr(rustfmt, rustfmt_skip)] const TRAIT_METHODS: [(&'static str, usize, SelfKind, OutType, &'static str); 30] = [ ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"), ("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"), ("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"), ("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"), ("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"), ("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"), ("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"), ("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"), ("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"), ("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"), ("default", 0, SelfKind::No, OutType::Any, "std::default::Default"), ("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"), ("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"), ("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"), ("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"), ("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"), ("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"), ("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"), ("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"), ("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"), ("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"), ("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"), ("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"), ("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"), ("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"), ("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"), ("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"), ("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"), ("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"), ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"), ]; #[cfg_attr(rustfmt, rustfmt_skip)] const PATTERN_METHODS: [(&'static str, usize); 17] = [ ("contains", 1), ("starts_with", 1), ("ends_with", 1), ("find", 1), ("rfind", 1), ("split", 1), ("rsplit", 1), ("split_terminator", 1), ("rsplit_terminator", 1), ("splitn", 2), ("rsplitn", 2), ("matches", 1), ("rmatches", 1), ("match_indices", 1), ("rmatch_indices", 1), ("trim_left_matches", 1), ("trim_right_matches", 1), ]; #[derive(Clone, Copy)] enum SelfKind { Value, Ref, RefMut, No, } impl SelfKind { fn matches(self, slf: &hir::ExplicitSelf, allow_value_for_ref: bool) -> bool { match (self, &slf.node) { (SelfKind::Value, &hir::SelfKind::Value(_)) | (SelfKind::Ref, &hir::SelfKind::Region(_, hir::Mutability::MutImmutable)) | (SelfKind::RefMut, &hir::SelfKind::Region(_, hir::Mutability::MutMutable)) => true, (SelfKind::Ref, &hir::SelfKind::Value(_)) | (SelfKind::RefMut, &hir::SelfKind::Value(_)) => allow_value_for_ref, (_, &hir::SelfKind::Explicit(ref ty, _)) => self.matches_explicit_type(ty, allow_value_for_ref), _ => false, } } fn matches_explicit_type(self, ty: &hir::Ty, allow_value_for_ref: bool) -> bool { match (self, &ty.node) { (SelfKind::Value, &hir::TyPath(..)) | (SelfKind::Ref, &hir::TyRptr(_, hir::MutTy { mutbl: hir::Mutability::MutImmutable, .. })) | (SelfKind::RefMut, &hir::TyRptr(_, hir::MutTy { mutbl: hir::Mutability::MutMutable, .. })) => true, (SelfKind::Ref, &hir::TyPath(..)) | (SelfKind::RefMut, &hir::TyPath(..)) => allow_value_for_ref, _ => false, } } fn description(&self) -> &'static str { match *self { SelfKind::Value => "self by value", SelfKind::Ref => "self by reference", SelfKind::RefMut => "self by mutable reference", SelfKind::No => "no self", } } } impl Convention { fn check(&self, other: &str) -> bool { match *self { Convention::Eq(this) => this == other, Convention::StartsWith(this) => other.starts_with(this) && this != other, } } } impl fmt::Display for Convention { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { match *self { Convention::Eq(this) => this.fmt(f), Convention::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)), } } } #[derive(Clone, Copy)] enum OutType { Unit, Bool, Any, Ref, } impl OutType { fn matches(&self, ty: &hir::FunctionRetTy) -> bool { match (self, ty) { (&OutType::Unit, &hir::DefaultReturn(_)) => true, (&OutType::Unit, &hir::Return(ref ty)) if ty.node == hir::TyTup(vec![].into()) => true, (&OutType::Bool, &hir::Return(ref ty)) if is_bool(ty) => true, (&OutType::Any, &hir::Return(ref ty)) if ty.node != hir::TyTup(vec![].into()) => true, (&OutType::Ref, &hir::Return(ref ty)) => matches!(ty.node, hir::TyRptr(_, _)), _ => false, } } } fn is_bool(ty: &hir::Ty) -> bool { if let hir::TyPath(ref p) = ty.node { match_path(p, &["bool"]) } else { false } }