254 lines
8.6 KiB
Rust
254 lines
8.6 KiB
Rust
use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
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use clippy_utils::macros::{is_format_macro, root_macro_call_first_node, FormatArgsArg, FormatArgsExpn};
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use clippy_utils::{get_parent_as_impl, is_diag_trait_item, path_to_local, peel_ref_operators};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, Impl, ImplItem, ImplItemKind, QPath};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::{sym, symbol::kw, Symbol};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for format trait implementations (e.g. `Display`) with a recursive call to itself
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/// which uses `self` as a parameter.
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/// This is typically done indirectly with the `write!` macro or with `to_string()`.
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///
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/// ### Why is this bad?
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/// This will lead to infinite recursion and a stack overflow.
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///
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/// ### Example
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///
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/// ```rust
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/// use std::fmt;
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///
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/// struct Structure(i32);
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/// impl fmt::Display for Structure {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f, "{}", self.to_string())
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/// }
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/// }
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///
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/// ```
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/// Use instead:
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/// ```rust
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/// use std::fmt;
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///
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/// struct Structure(i32);
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/// impl fmt::Display for Structure {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f, "{}", self.0)
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/// }
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/// }
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/// ```
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#[clippy::version = "1.48.0"]
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pub RECURSIVE_FORMAT_IMPL,
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correctness,
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"Format trait method called while implementing the same Format trait"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for use of `println`, `print`, `eprintln` or `eprint` in an
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/// implementation of a formatting trait.
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///
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/// ### Why is this bad?
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/// Using a print macro is likely unintentional since formatting traits
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/// should write to the `Formatter`, not stdout/stderr.
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///
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/// ### Example
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/// ```rust
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/// use std::fmt::{Display, Error, Formatter};
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///
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/// struct S;
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/// impl Display for S {
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/// fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
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/// println!("S");
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///
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/// Ok(())
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/// }
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// use std::fmt::{Display, Error, Formatter};
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///
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/// struct S;
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/// impl Display for S {
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/// fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
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/// writeln!(f, "S");
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///
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/// Ok(())
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/// }
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/// }
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/// ```
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#[clippy::version = "1.61.0"]
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pub PRINT_IN_FORMAT_IMPL,
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suspicious,
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"use of a print macro in a formatting trait impl"
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}
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#[derive(Clone, Copy)]
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struct FormatTrait {
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/// e.g. `sym::Display`
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name: Symbol,
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/// `f` in `fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {}`
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formatter_name: Option<Symbol>,
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}
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#[derive(Default)]
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pub struct FormatImpl {
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// Whether we are inside Display or Debug trait impl - None for neither
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format_trait_impl: Option<FormatTrait>,
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}
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impl FormatImpl {
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pub fn new() -> Self {
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Self {
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format_trait_impl: None,
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}
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}
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}
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impl_lint_pass!(FormatImpl => [RECURSIVE_FORMAT_IMPL, PRINT_IN_FORMAT_IMPL]);
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impl<'tcx> LateLintPass<'tcx> for FormatImpl {
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fn check_impl_item(&mut self, cx: &LateContext<'_>, impl_item: &ImplItem<'_>) {
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self.format_trait_impl = is_format_trait_impl(cx, impl_item);
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}
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fn check_impl_item_post(&mut self, cx: &LateContext<'_>, impl_item: &ImplItem<'_>) {
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// Assume no nested Impl of Debug and Display within eachother
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if is_format_trait_impl(cx, impl_item).is_some() {
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self.format_trait_impl = None;
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}
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}
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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let Some(format_trait_impl) = self.format_trait_impl else { return };
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if format_trait_impl.name == sym::Display {
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check_to_string_in_display(cx, expr);
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}
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check_self_in_format_args(cx, expr, format_trait_impl);
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check_print_in_format_impl(cx, expr, format_trait_impl);
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}
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}
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fn check_to_string_in_display(cx: &LateContext<'_>, expr: &Expr<'_>) {
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if_chain! {
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// Get the hir_id of the object we are calling the method on
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if let ExprKind::MethodCall(path, [ref self_arg, ..], _) = expr.kind;
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// Is the method to_string() ?
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if path.ident.name == sym!(to_string);
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// Is the method a part of the ToString trait? (i.e. not to_string() implemented
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// separately)
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if let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
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if is_diag_trait_item(cx, expr_def_id, sym::ToString);
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// Is the method is called on self
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if let ExprKind::Path(QPath::Resolved(_, path)) = self_arg.kind;
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if let [segment] = path.segments;
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if segment.ident.name == kw::SelfLower;
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then {
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span_lint(
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cx,
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RECURSIVE_FORMAT_IMPL,
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expr.span,
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"using `self.to_string` in `fmt::Display` implementation will cause infinite recursion",
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);
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}
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}
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}
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fn check_self_in_format_args<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, impl_trait: FormatTrait) {
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// Check each arg in format calls - do we ever use Display on self (directly or via deref)?
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if_chain! {
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if let Some(outer_macro) = root_macro_call_first_node(cx, expr);
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if let macro_def_id = outer_macro.def_id;
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if let Some(format_args) = FormatArgsExpn::find_nested(cx, expr, outer_macro.expn);
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if is_format_macro(cx, macro_def_id);
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if let Some(args) = format_args.args();
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then {
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for arg in args {
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if arg.format_trait != impl_trait.name {
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continue;
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}
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check_format_arg_self(cx, expr, &arg, impl_trait);
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}
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}
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}
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}
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fn check_format_arg_self(cx: &LateContext<'_>, expr: &Expr<'_>, arg: &FormatArgsArg<'_>, impl_trait: FormatTrait) {
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// Handle multiple dereferencing of references e.g. &&self
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// Handle dereference of &self -> self that is equivalent (i.e. via *self in fmt() impl)
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// Since the argument to fmt is itself a reference: &self
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let reference = peel_ref_operators(cx, arg.value);
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let map = cx.tcx.hir();
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// Is the reference self?
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if path_to_local(reference).map(|x| map.name(x)) == Some(kw::SelfLower) {
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let FormatTrait { name, .. } = impl_trait;
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span_lint(
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cx,
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RECURSIVE_FORMAT_IMPL,
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expr.span,
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&format!("using `self` as `{name}` in `impl {name}` will cause infinite recursion"),
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);
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}
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}
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fn check_print_in_format_impl(cx: &LateContext<'_>, expr: &Expr<'_>, impl_trait: FormatTrait) {
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if_chain! {
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if let Some(macro_call) = root_macro_call_first_node(cx, expr);
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if let Some(name) = cx.tcx.get_diagnostic_name(macro_call.def_id);
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then {
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let replacement = match name {
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sym::print_macro | sym::eprint_macro => "write",
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sym::println_macro | sym::eprintln_macro => "writeln",
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_ => return,
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};
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let name = name.as_str().strip_suffix("_macro").unwrap();
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span_lint_and_sugg(
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cx,
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PRINT_IN_FORMAT_IMPL,
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macro_call.span,
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&format!("use of `{}!` in `{}` impl", name, impl_trait.name),
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"replace with",
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if let Some(formatter_name) = impl_trait.formatter_name {
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format!("{}!({}, ..)", replacement, formatter_name)
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} else {
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format!("{}!(..)", replacement)
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},
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Applicability::HasPlaceholders,
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);
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}
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}
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}
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fn is_format_trait_impl(cx: &LateContext<'_>, impl_item: &ImplItem<'_>) -> Option<FormatTrait> {
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if_chain! {
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if impl_item.ident.name == sym::fmt;
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if let ImplItemKind::Fn(_, body_id) = impl_item.kind;
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if let Some(Impl { of_trait: Some(trait_ref),..}) = get_parent_as_impl(cx.tcx, impl_item.hir_id());
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if let Some(did) = trait_ref.trait_def_id();
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if let Some(name) = cx.tcx.get_diagnostic_name(did);
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if matches!(name, sym::Debug | sym::Display);
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then {
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let body = cx.tcx.hir().body(body_id);
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let formatter_name = body.params.get(1)
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.and_then(|param| param.pat.simple_ident())
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.map(|ident| ident.name);
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Some(FormatTrait {
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name,
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formatter_name,
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})
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} else {
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None
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}
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}
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}
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