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Auto merge of rust-lang#7743 - smoelius:master, r=camsteffen
Add `format_in_format_args` and `to_string_in_format_args` lints Fixes rust-lang#7667 and rust-lang#7729 I put these in `perf` since that was one of `@jplatte's` suggestions, and `redundant_clone` (which I consider to be similar) lives there as well. However, I am open to changing the category or anything else. r? `@camsteffen` changelog: Add `format_in_format_args` and `to_string_in_format_args` lints
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,223 @@ | ||
| use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then}; | ||
| use clippy_utils::higher::{FormatArgsArg, FormatArgsExpn, FormatExpn}; | ||
| use clippy_utils::source::snippet_opt; | ||
| use clippy_utils::ty::implements_trait; | ||
| use clippy_utils::{is_diag_trait_item, match_def_path, paths}; | ||
| use if_chain::if_chain; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::{Expr, ExprKind}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_middle::ty::adjustment::{Adjust, Adjustment}; | ||
| use rustc_middle::ty::Ty; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
| use rustc_span::{sym, BytePos, ExpnData, ExpnKind, Span, Symbol}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Detects `format!` within the arguments of another macro that does | ||
| /// formatting such as `format!` itself, `write!` or `println!`. Suggests | ||
| /// inlining the `format!` call. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// The recommended code is both shorter and avoids a temporary allocation. | ||
| /// | ||
| /// ### Example | ||
| /// ```rust | ||
| /// # use std::panic::Location; | ||
| /// println!("error: {}", format!("something failed at {}", Location::caller())); | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust | ||
| /// # use std::panic::Location; | ||
| /// println!("error: something failed at {}", Location::caller()); | ||
| /// ``` | ||
| pub FORMAT_IN_FORMAT_ARGS, | ||
| perf, | ||
| "`format!` used in a macro that does formatting" | ||
| } | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Checks for [`ToString::to_string`](https://doc.rust-lang.org/std/string/trait.ToString.html#tymethod.to_string) | ||
| /// applied to a type that implements [`Display`](https://doc.rust-lang.org/std/fmt/trait.Display.html) | ||
| /// in a macro that does formatting. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// Since the type implements `Display`, the use of `to_string` is | ||
| /// unnecessary. | ||
| /// | ||
| /// ### Example | ||
| /// ```rust | ||
| /// # use std::panic::Location; | ||
| /// println!("error: something failed at {}", Location::caller().to_string()); | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust | ||
| /// # use std::panic::Location; | ||
| /// println!("error: something failed at {}", Location::caller()); | ||
| /// ``` | ||
| pub TO_STRING_IN_FORMAT_ARGS, | ||
| perf, | ||
| "`to_string` applied to a type that implements `Display` in format args" | ||
| } | ||
|
|
||
| declare_lint_pass!(FormatArgs => [FORMAT_IN_FORMAT_ARGS, TO_STRING_IN_FORMAT_ARGS]); | ||
|
|
||
| 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, | ||
| ]; | ||
|
|
||
| const FORMAT_MACRO_DIAG_ITEMS: &[Symbol] = &[sym::format_macro, sym::std_panic_macro]; | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for FormatArgs { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { | ||
| if_chain! { | ||
| if let Some(format_args) = FormatArgsExpn::parse(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() { | ||
| if !arg.is_display() { | ||
| continue; | ||
| } | ||
| if arg.has_string_formatting() { | ||
| continue; | ||
| } | ||
| if is_aliased(&args, i) { | ||
| continue; | ||
| } | ||
| check_format_in_format_args(cx, outermost_expn_data.call_site, name, arg); | ||
| check_to_string_in_format_args(cx, name, arg); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| 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 | ||
| } | ||
| } | ||
|
|
||
| fn check_format_in_format_args(cx: &LateContext<'_>, call_site: Span, name: Symbol, arg: &FormatArgsArg<'_>) { | ||
| if_chain! { | ||
| if FormatExpn::parse(arg.value).is_some(); | ||
| if !arg.value.span.ctxt().outer_expn_data().call_site.from_expansion(); | ||
| then { | ||
| span_lint_and_then( | ||
| cx, | ||
| FORMAT_IN_FORMAT_ARGS, | ||
| trim_semicolon(cx, call_site), | ||
| &format!("`format!` in `{}!` args", name), | ||
| |diag| { | ||
| diag.help(&format!( | ||
| "combine the `format!(..)` arguments with the outer `{}!(..)` call", | ||
| name | ||
| )); | ||
| diag.help("or consider changing `format!` to `format_args!`"); | ||
| }, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_to_string_in_format_args<'tcx>(cx: &LateContext<'tcx>, name: Symbol, arg: &FormatArgsArg<'tcx>) { | ||
| let value = arg.value; | ||
| if_chain! { | ||
| if !value.span.from_expansion(); | ||
| if let ExprKind::MethodCall(_, _, [receiver], _) = value.kind; | ||
| if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(value.hir_id); | ||
| if is_diag_trait_item(cx, method_def_id, sym::ToString); | ||
| let receiver_ty = cx.typeck_results().expr_ty(receiver); | ||
| if let Some(display_trait_id) = cx.tcx.get_diagnostic_item(sym::Display); | ||
| if let Some(receiver_snippet) = snippet_opt(cx, receiver.span); | ||
| then { | ||
| let (n_needed_derefs, target) = count_needed_derefs( | ||
| receiver_ty, | ||
| cx.typeck_results().expr_adjustments(receiver).iter(), | ||
| ); | ||
| if implements_trait(cx, target, display_trait_id, &[]) { | ||
| if n_needed_derefs == 0 { | ||
| span_lint_and_sugg( | ||
| cx, | ||
| TO_STRING_IN_FORMAT_ARGS, | ||
| value.span.with_lo(receiver.span.hi()), | ||
| &format!("`to_string` applied to a type that implements `Display` in `{}!` args", name), | ||
| "remove this", | ||
| String::new(), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } else { | ||
| span_lint_and_sugg( | ||
| cx, | ||
| TO_STRING_IN_FORMAT_ARGS, | ||
| value.span, | ||
| &format!("`to_string` applied to a type that implements `Display` in `{}!` args", name), | ||
| "use this", | ||
| format!("{:*>width$}{}", "", receiver_snippet, width = n_needed_derefs), | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // Returns true if `args[i]` "refers to" or "is referred to by" another argument. | ||
| fn is_aliased(args: &[FormatArgsArg<'_>], i: usize) -> bool { | ||
| let value = args[i].value; | ||
| args.iter() | ||
| .enumerate() | ||
| .any(|(j, arg)| i != j && std::ptr::eq(value, arg.value)) | ||
| } | ||
|
|
||
| fn trim_semicolon(cx: &LateContext<'_>, span: Span) -> Span { | ||
| snippet_opt(cx, span).map_or(span, |snippet| { | ||
| let snippet = snippet.trim_end_matches(';'); | ||
| span.with_hi(span.lo() + BytePos(u32::try_from(snippet.len()).unwrap())) | ||
| }) | ||
| } | ||
|
|
||
| fn count_needed_derefs<'tcx, I>(mut ty: Ty<'tcx>, mut iter: I) -> (usize, Ty<'tcx>) | ||
| where | ||
| I: Iterator<Item = &'tcx Adjustment<'tcx>>, | ||
| { | ||
| let mut n_total = 0; | ||
| let mut n_needed = 0; | ||
| loop { | ||
| if let Some(Adjustment { | ||
| kind: Adjust::Deref(overloaded_deref), | ||
| target, | ||
| }) = iter.next() | ||
| { | ||
| n_total += 1; | ||
| if overloaded_deref.is_some() { | ||
| n_needed = n_total; | ||
| } | ||
| ty = target; | ||
| } else { | ||
| return (n_needed, ty); | ||
| } | ||
| } | ||
| } |
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