diff --git a/CHANGELOG.md b/CHANGELOG.md index 461adb729..ff5aebbc8 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -973,6 +973,8 @@ Released 2018-09-13 [`ineffective_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#ineffective_bit_mask [`infallible_destructuring_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#infallible_destructuring_match [`infinite_iter`]: https://rust-lang.github.io/rust-clippy/master/index.html#infinite_iter +[`inherent_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#inherent_to_string +[`inherent_to_string_shadow_display`]: https://rust-lang.github.io/rust-clippy/master/index.html#inherent_to_string_shadow_display [`inline_always`]: https://rust-lang.github.io/rust-clippy/master/index.html#inline_always [`inline_fn_without_body`]: https://rust-lang.github.io/rust-clippy/master/index.html#inline_fn_without_body [`int_plus_one`]: https://rust-lang.github.io/rust-clippy/master/index.html#int_plus_one diff --git a/README.md b/README.md index 24bda9bbe..1e649d898 100644 --- a/README.md +++ b/README.md @@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code. -[There are 306 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html) +[There are 308 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html) We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you: diff --git a/clippy_lints/src/inherent_to_string.rs b/clippy_lints/src/inherent_to_string.rs new file mode 100644 index 000000000..57ffdf78d --- /dev/null +++ b/clippy_lints/src/inherent_to_string.rs @@ -0,0 +1,148 @@ +use if_chain::if_chain; +use rustc::hir::{ImplItem, ImplItemKind}; +use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; +use rustc::{declare_lint_pass, declare_tool_lint}; + +use crate::utils::{ + get_trait_def_id, implements_trait, in_macro_or_desugar, match_type, paths, return_ty, span_help_and_lint, + trait_ref_of_method, walk_ptrs_ty, +}; + +declare_clippy_lint! { + /// **What id does:** Checks for the definition of inherent methods with a signature of `to_string(&self) -> String`. + /// + /// **Why is this bad?** This method is also implicitly defined if a type implements the `Display` trait. As the functionality of `Display` is much more versatile, it should be preferred. + /// + /// **Known problems:** None + /// + /// ** Example:** + /// + /// ```rust,ignore + /// // Bad + /// pub struct A; + /// + /// impl A { + /// pub fn to_string(&self) -> String { + /// "I am A".to_string() + /// } + /// } + /// // Good + /// use std::fmt; + /// + /// pub struct A; + /// + /// impl fmt::Display for A { + /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + /// write!(f, "I am A") + /// } + /// } + /// ``` + pub INHERENT_TO_STRING, + style, + "type implements inherent method 'to_string()', but should instead implement the 'Display' trait" +} + +declare_clippy_lint! { + /// **What id does:** Checks for the definition of inherent methods with a signature of `to_string(&self) -> String` and if the type implementing this method also implements the `Display` trait. + /// + /// **Why is this bad?** This method is also implicitly defined if a type implements the 'Display' trait. The less versatile inherent method will then shadow the implementation introduced by `Display`. + /// + /// **Known problems:** The inherent method will shadow the implementation by `Display`. If they behave differently, this may lead to confusing situations for users of the respective type. + /// + /// ** Example:** + /// + /// ```rust,ignore + /// // Bad + /// use std::fmt; + /// + /// pub struct A; + /// + /// impl A { + /// pub fn to_string(&self) -> String { + /// "I am A".to_string() + /// } + /// } + /// + /// impl fmt::Display for A { + /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + /// write!(f, "I am A, too") + /// } + /// } + /// // Good + /// use std::fmt; + /// + /// pub struct A; + /// + /// impl fmt::Display for A { + /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + /// write!(f, "I am A") + /// } + /// } + /// ``` + pub INHERENT_TO_STRING_SHADOW_DISPLAY, + correctness, + "type implements inherent method 'to_string()', which gets shadowed by the implementation of the 'Display' trait " +} + +declare_lint_pass!(InherentToString => [INHERENT_TO_STRING, INHERENT_TO_STRING_SHADOW_DISPLAY]); + +impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InherentToString { + fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, impl_item: &'tcx ImplItem) { + if in_macro_or_desugar(impl_item.span) { + return; + } + + if_chain! { + // Check if item is a method, called to_string and has a parameter 'self' + if let ImplItemKind::Method(ref signature, _) = impl_item.node; + if impl_item.ident.name.as_str() == "to_string"; + let decl = &signature.decl; + if decl.implicit_self.has_implicit_self(); + + // Check if return type is String + if match_type(cx, return_ty(cx, impl_item.hir_id), &paths::STRING); + + // Filters instances of to_string which are required by a trait + if trait_ref_of_method(cx, impl_item.hir_id).is_none(); + + then { + show_lint(cx, impl_item); + } + } + } +} + +fn show_lint(cx: &LateContext<'_, '_>, item: &ImplItem) { + let display_trait_id = + get_trait_def_id(cx, &["core", "fmt", "Display"]).expect("Failed to get trait ID of 'Display'!"); + + // Get the real type of 'self' + let fn_def_id = cx.tcx.hir().local_def_id(item.hir_id); + let self_type = cx.tcx.fn_sig(fn_def_id).input(0); + let self_type = walk_ptrs_ty(self_type.skip_binder()); + + // Emit either a warning or an error + if implements_trait(cx, self_type, display_trait_id, &[]) { + span_help_and_lint( + cx, + INHERENT_TO_STRING_SHADOW_DISPLAY, + item.span, + &format!( + "type '{}' implements inherent method 'to_string() -> String' which shadows the implementation of 'Display'", + self_type.to_string() + ), + &format!("remove the inherent method from type '{}'", self_type.to_string()) + ); + } else { + span_help_and_lint( + cx, + INHERENT_TO_STRING, + item.span, + &format!( + "implementation of inherent method 'to_string() -> String' for type '{}'", + self_type.to_string() + ), + &format!("implement trait 'Display' for type '{}' instead", self_type.to_string()), + ); + } +} diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 369a736aa..de7a213d7 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -195,6 +195,7 @@ pub mod indexing_slicing; pub mod infallible_destructuring_match; pub mod infinite_iter; pub mod inherent_impl; +pub mod inherent_to_string; pub mod inline_fn_without_body; pub mod int_plus_one; pub mod integer_division; @@ -585,6 +586,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) { reg.register_late_lint_pass(box path_buf_push_overwrite::PathBufPushOverwrite); reg.register_late_lint_pass(box checked_conversions::CheckedConversions); reg.register_late_lint_pass(box integer_division::IntegerDivision); + reg.register_late_lint_pass(box inherent_to_string::InherentToString); reg.register_lint_group("clippy::restriction", Some("clippy_restriction"), vec![ arithmetic::FLOAT_ARITHMETIC, @@ -725,6 +727,8 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) { indexing_slicing::OUT_OF_BOUNDS_INDEXING, infallible_destructuring_match::INFALLIBLE_DESTRUCTURING_MATCH, infinite_iter::INFINITE_ITER, + inherent_to_string::INHERENT_TO_STRING, + inherent_to_string::INHERENT_TO_STRING_SHADOW_DISPLAY, inline_fn_without_body::INLINE_FN_WITHOUT_BODY, int_plus_one::INT_PLUS_ONE, invalid_ref::INVALID_REF, @@ -913,6 +917,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) { formatting::SUSPICIOUS_ASSIGNMENT_FORMATTING, formatting::SUSPICIOUS_ELSE_FORMATTING, infallible_destructuring_match::INFALLIBLE_DESTRUCTURING_MATCH, + inherent_to_string::INHERENT_TO_STRING, len_zero::LEN_WITHOUT_IS_EMPTY, len_zero::LEN_ZERO, let_if_seq::USELESS_LET_IF_SEQ, @@ -1075,6 +1080,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) { functions::NOT_UNSAFE_PTR_ARG_DEREF, indexing_slicing::OUT_OF_BOUNDS_INDEXING, infinite_iter::INFINITE_ITER, + inherent_to_string::INHERENT_TO_STRING_SHADOW_DISPLAY, inline_fn_without_body::INLINE_FN_WITHOUT_BODY, invalid_ref::INVALID_REF, literal_representation::MISTYPED_LITERAL_SUFFIXES, diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 8c49a3b18..59eb92593 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -6,7 +6,7 @@ pub use lint::Lint; pub use lint::LINT_LEVELS; // begin lint list, do not remove this comment, it’s used in `update_lints` -pub const ALL_LINTS: [Lint; 306] = [ +pub const ALL_LINTS: [Lint; 308] = [ Lint { name: "absurd_extreme_comparisons", group: "correctness", @@ -728,6 +728,20 @@ pub const ALL_LINTS: [Lint; 306] = [ deprecation: None, module: "infinite_iter", }, + Lint { + name: "inherent_to_string", + group: "style", + desc: "type implements inherent method \'to_string()\', but should instead implement the \'Display\' trait", + deprecation: None, + module: "inherent_to_string", + }, + Lint { + name: "inherent_to_string_shadow_display", + group: "correctness", + desc: "type implements inherent method \'to_string()\', which gets shadowed by the implementation of the \'Display\' trait ", + deprecation: None, + module: "inherent_to_string", + }, Lint { name: "inline_always", group: "pedantic", diff --git a/tests/ui/inherent_to_string.rs b/tests/ui/inherent_to_string.rs new file mode 100644 index 000000000..78f24a3c9 --- /dev/null +++ b/tests/ui/inherent_to_string.rs @@ -0,0 +1,84 @@ +#![warn(clippy::inherent_to_string)] +//#![deny(clippy::inherent_to_string_shadow)] + +use std::fmt; + +trait FalsePositive { + fn to_string(&self) -> String; +} + +struct A; +struct B; +struct C; +struct D; +struct E; + +impl A { + // Should be detected; emit warning + fn to_string(&self) -> String { + "A.to_string()".to_string() + } + + // Should not be detected as it does not match the function signature + fn to_str(&self) -> String { + "A.to_str()".to_string() + } +} + +// Should not be detected as it is a free function +fn to_string() -> String { + "free to_string()".to_string() +} + +impl B { + // Should not be detected, wrong return type + fn to_string(&self) -> i32 { + 42 + } +} + +impl C { + // Should be detected and emit error as C also implements Display + fn to_string(&self) -> String { + "C.to_string()".to_string() + } +} + +impl fmt::Display for C { + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { + write!(f, "impl Display for C") + } +} + +impl FalsePositive for D { + // Should not be detected, as it is a trait function + fn to_string(&self) -> String { + "impl FalsePositive for D".to_string() + } +} + +impl E { + // Should not be detected, as it is not bound to an instance + fn to_string() -> String { + "E::to_string()".to_string() + } +} + +fn main() { + let a = A; + a.to_string(); + a.to_str(); + + to_string(); + + let b = B; + b.to_string(); + + let c = C; + C.to_string(); + + let d = D; + d.to_string(); + + E::to_string(); +} diff --git a/tests/ui/inherent_to_string.stderr b/tests/ui/inherent_to_string.stderr new file mode 100644 index 000000000..85fb06a22 --- /dev/null +++ b/tests/ui/inherent_to_string.stderr @@ -0,0 +1,24 @@ +error: implementation of inherent method 'to_string() -> String' for type 'A' + --> $DIR/inherent_to_string.rs:18:5 + | +LL | / fn to_string(&self) -> String { +LL | | "A.to_string()".to_string() +LL | | } + | |_____^ + | + = note: `-D clippy::inherent-to-string` implied by `-D warnings` + = help: implement trait 'Display' for type 'A' instead + +error: type 'C' implements inherent method 'to_string() -> String' which shadows the implementation of 'Display' + --> $DIR/inherent_to_string.rs:42:5 + | +LL | / fn to_string(&self) -> String { +LL | | "C.to_string()".to_string() +LL | | } + | |_____^ + | + = note: #[deny(clippy::inherent_to_string_shadow_display)] on by default + = help: remove the inherent method from type 'C' + +error: aborting due to 2 previous errors +