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The to_string_in_display lint is renamed to recursive_format_impl A check is added for the use of self formatted with Display or Debug inside any format string in the same impl The to_string_in_display check is kept as is - like in the format_in_format_args lint For now only Display and Debug are checked This could also be extended to other Format traits (Binary, etc.)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,269 @@ | ||
| use clippy_utils::diagnostics::span_lint; | ||
| use clippy_utils::macros::{FormatArgsArg, FormatArgsExpn}; | ||
| use clippy_utils::{is_diag_trait_item, match_def_path, path_to_local_id, paths}; | ||
| use if_chain::if_chain; | ||
| use rustc_hir::{Expr, ExprKind, HirId, Impl, ImplItem, ImplItemKind, Item, ItemKind, UnOp}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_tool_lint, impl_lint_pass}; | ||
| use rustc_span::{sym, ExpnData, ExpnKind, Symbol}; | ||
|
|
||
| const FORMAT_MACRO_PATHS: &[&[&str]] = &[ | ||
| &paths::FORMAT_ARGS_MACRO, | ||
| &paths::ASSERT_EQ_MACRO, | ||
| &paths::ASSERT_MACRO, | ||
| &paths::ASSERT_NE_MACRO, | ||
| &paths::EPRINT_MACRO, | ||
| &paths::EPRINTLN_MACRO, | ||
| &paths::PRINT_MACRO, | ||
| &paths::PRINTLN_MACRO, | ||
| &paths::WRITE_MACRO, | ||
| &paths::WRITELN_MACRO, | ||
| ]; | ||
|
|
||
| #[derive(Clone, Copy)] | ||
| enum ImplTrait { | ||
| Debug, | ||
| Display, | ||
| } | ||
|
|
||
| const FORMAT_MACRO_DIAG_ITEMS: &[Symbol] = &[sym::format_macro, sym::std_panic_macro]; | ||
|
|
||
| fn outermost_expn_data(expn_data: ExpnData) -> ExpnData { | ||
| if expn_data.call_site.from_expansion() { | ||
| outermost_expn_data(expn_data.call_site.ctxt().outer_expn_data()) | ||
| } else { | ||
| expn_data | ||
| } | ||
| } | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Checks for recursive use of `Display` or `Debug` traits inside their implementation. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// This is unconditional recursion and so will lead to infinite | ||
| /// recursion and a stack overflow. | ||
| /// | ||
| /// ### Example | ||
| /// | ||
| /// ```rust | ||
| /// use std::fmt; | ||
| /// | ||
| /// struct Structure(i32); | ||
| /// impl fmt::Display for Structure { | ||
| /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | ||
| /// write!(f, "{}", self.to_string()) | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust | ||
| /// use std::fmt; | ||
| /// | ||
| /// struct Structure(i32); | ||
| /// impl fmt::Display for Structure { | ||
| /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | ||
| /// write!(f, "{}", self.0) | ||
| /// } | ||
| /// } | ||
| /// ``` | ||
| #[clippy::version = "1.48.0"] | ||
| pub RECURSIVE_FORMAT_IMPL, | ||
| correctness, | ||
| "Format trait method called while implementing the same Format trait" | ||
| } | ||
|
|
||
| #[derive(Default)] | ||
| pub struct RecursiveFormatImpl { | ||
| // Whether we are inside Display or Debug trait impl - None for neither | ||
| format_trait_impl: Option<ImplTrait>, | ||
| // hir_id of self parameter of method inside Display Impl - i.e. fmt(&self) | ||
| self_hir_id: Option<HirId>, | ||
| } | ||
|
|
||
| impl RecursiveFormatImpl { | ||
| pub fn new() -> Self { | ||
| Self { | ||
| format_trait_impl: None, | ||
| self_hir_id: None, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl_lint_pass!(RecursiveFormatImpl => [RECURSIVE_FORMAT_IMPL]); | ||
|
|
||
| impl LateLintPass<'_> for RecursiveFormatImpl { | ||
| fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) { | ||
| if let Some(format_trait_impl) = is_format_trait_impl(cx, item) { | ||
| self.format_trait_impl = Some(format_trait_impl); | ||
| } | ||
| } | ||
|
|
||
| fn check_item_post(&mut self, cx: &LateContext<'_>, item: &Item<'_>) { | ||
| // Assume no nested Impl of Debug and Display within eachother | ||
| if is_format_trait_impl(cx, item).is_some() { | ||
| self.format_trait_impl = None; | ||
| self.self_hir_id = None; | ||
| } | ||
| } | ||
|
|
||
| fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &ImplItem<'_>) { | ||
| if_chain! { | ||
| // If we are in Display or Debug impl, then get hir_id for self in method impl - i.e. fmt(&self) | ||
| if self.format_trait_impl.is_some(); | ||
| if let ImplItemKind::Fn(.., body_id) = &impl_item.kind; | ||
| let body = cx.tcx.hir().body(*body_id); | ||
| if !body.params.is_empty(); | ||
| then { | ||
| let self_param = &body.params[0]; | ||
| self.self_hir_id = Some(self_param.pat.hir_id); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) { | ||
| if let Some(self_hir_id) = self.self_hir_id { | ||
| match self.format_trait_impl { | ||
| Some(ImplTrait::Display) => { | ||
| check_to_string_in_display(cx, expr, self_hir_id); | ||
| check_self_in_format_args(cx, expr, self_hir_id, ImplTrait::Display); | ||
| }, | ||
| Some(ImplTrait::Debug) => { | ||
| check_self_in_format_args(cx, expr, self_hir_id, ImplTrait::Debug); | ||
| }, | ||
| None => {}, | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_to_string_in_display(cx: &LateContext<'_>, expr: &Expr<'_>, self_hir_id: HirId) { | ||
| if_chain! { | ||
| // Get the hir_id of the object we are calling the method on | ||
| if let ExprKind::MethodCall(path, _, [ref self_arg, ..], _) = expr.kind; | ||
| // Is the method to_string() ? | ||
| if path.ident.name == sym!(to_string); | ||
| // Is the method a part of the ToString trait? (i.e. not to_string() implemented | ||
| // separately) | ||
| if let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id); | ||
| if is_diag_trait_item(cx, expr_def_id, sym::ToString); | ||
| // Is the method is called on self | ||
| if path_to_local_id(self_arg, self_hir_id); | ||
| then { | ||
| span_lint( | ||
| cx, | ||
| RECURSIVE_FORMAT_IMPL, | ||
| expr.span, | ||
| "using `to_string` in `fmt::Display` implementation might lead to infinite recursion", | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_self_in_format_args(cx: &LateContext<'_>, expr: &Expr<'_>, self_hir_id: HirId, impl_trait: ImplTrait) { | ||
| // Check each arg in format calls - do we ever use Display on self (directly or via deref)? | ||
| if_chain! { | ||
| if let Some(format_args) = FormatArgsExpn::parse(cx, expr); | ||
| let expr_expn_data = expr.span.ctxt().outer_expn_data(); | ||
| let outermost_expn_data = outermost_expn_data(expr_expn_data); | ||
| if let Some(macro_def_id) = outermost_expn_data.macro_def_id; | ||
| if FORMAT_MACRO_PATHS | ||
| .iter() | ||
| .any(|path| match_def_path(cx, macro_def_id, path)) | ||
| || FORMAT_MACRO_DIAG_ITEMS | ||
| .iter() | ||
| .any(|diag_item| cx.tcx.is_diagnostic_item(*diag_item, macro_def_id)); | ||
| if let ExpnKind::Macro(_, _name) = outermost_expn_data.kind; | ||
| if let Some(args) = format_args.args(); | ||
| then { | ||
| for (_i, arg) in args.iter().enumerate() { | ||
| match impl_trait { | ||
| // In Display, we only care about Display (it is okay to use Debug) | ||
| ImplTrait::Display => { | ||
| if arg.format_trait != sym::Display { | ||
| continue; | ||
| }}, | ||
| // In Debug, we only care about Debug (it is okay to use Display and ToString) | ||
| ImplTrait::Debug => { | ||
| if arg.format_trait != sym::Debug { | ||
| continue; | ||
| }}, | ||
|
|
||
| }; | ||
| check_format_arg_self(cx, expr, self_hir_id, arg, impl_trait); | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_format_arg_self( | ||
| cx: &LateContext<'_>, | ||
| expr: &Expr<'_>, | ||
| self_hir_id: HirId, | ||
| arg: &FormatArgsArg<'_>, | ||
| impl_trait: ImplTrait, | ||
| ) { | ||
| // Handle multiple dereferencing of references e.g. &&self | ||
| // Handle single dereference of &self -> self that is equivalent (i.e. via *self in fmt() impl) | ||
| // Since the argument to fmt is itself a reference: &self | ||
| let reference = single_deref(deref_expr(arg.value)); | ||
| if path_to_local_id(reference, self_hir_id) { | ||
| match impl_trait { | ||
| ImplTrait::Display => { | ||
| span_lint( | ||
| cx, | ||
| RECURSIVE_FORMAT_IMPL, | ||
| expr.span, | ||
| "using `self` as Display in `fmt::Display` implementation might lead to infinite recursion", | ||
| ); | ||
| }, | ||
| ImplTrait::Debug => { | ||
| span_lint( | ||
| cx, | ||
| RECURSIVE_FORMAT_IMPL, | ||
| expr.span, | ||
| "using `self` as Debug in `fmt::Debug` implementation might lead to infinite recursion", | ||
| ); | ||
| }, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn deref_expr<'a, 'b>(expr: &'a Expr<'b>) -> &'a Expr<'b> { | ||
| if let ExprKind::AddrOf(_, _, reference) = expr.kind { | ||
| deref_expr(reference) | ||
| } else { | ||
| expr | ||
| } | ||
| } | ||
|
|
||
| fn single_deref<'a, 'b>(expr: &'a Expr<'b>) -> &'a Expr<'b> { | ||
| if let ExprKind::Unary(UnOp::Deref, ex) = expr.kind { | ||
| ex | ||
| } else { | ||
| expr | ||
| } | ||
| } | ||
|
|
||
| fn is_format_trait_impl(cx: &LateContext<'_>, item: &Item<'_>) -> Option<ImplTrait> { | ||
| if_chain! { | ||
| // Are we at an Impl? | ||
| if let ItemKind::Impl(Impl { of_trait: Some(trait_ref), .. }) = &item.kind; | ||
| if let Some(did) = trait_ref.trait_def_id(); | ||
| then { | ||
| // Is it for Display trait? | ||
| if match_def_path(cx, did, &paths::DISPLAY_TRAIT) { | ||
| Some(ImplTrait::Display) | ||
| } | ||
| // Is it for Debug trait? | ||
| else if match_def_path(cx, did, &paths::DEBUG_TRAIT) { | ||
| Some(ImplTrait::Debug) | ||
| } else { | ||
| None | ||
| } | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
| } |
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