|
| 1 | +use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then}; |
| 2 | +use clippy_utils::higher::{FormatArgsArg, FormatArgsExpn, FormatExpn}; |
| 3 | +use clippy_utils::source::snippet_opt; |
| 4 | +use clippy_utils::ty::implements_trait; |
| 5 | +use clippy_utils::{is_diag_trait_item, match_def_path, paths}; |
| 6 | +use if_chain::if_chain; |
| 7 | +use rustc_errors::Applicability; |
| 8 | +use rustc_hir::{Expr, ExprKind}; |
| 9 | +use rustc_lint::{LateContext, LateLintPass}; |
| 10 | +use rustc_middle::ty::adjustment::{Adjust, Adjustment}; |
| 11 | +use rustc_middle::ty::Ty; |
| 12 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 13 | +use rustc_span::{sym, BytePos, ExpnData, ExpnKind, Span, Symbol}; |
| 14 | + |
| 15 | +declare_clippy_lint! { |
| 16 | + /// ### What it does |
| 17 | + /// Detects `format!` within the arguments of another macro that does |
| 18 | + /// formatting such as `format!` itself, `write!` or `println!`. Suggests |
| 19 | + /// inlining the `format!` call. |
| 20 | + /// |
| 21 | + /// ### Why is this bad? |
| 22 | + /// The recommended code is both shorter and avoids a temporary allocation. |
| 23 | + /// |
| 24 | + /// ### Example |
| 25 | + /// ```rust |
| 26 | + /// # use std::panic::Location; |
| 27 | + /// println!("error: {}", format!("something failed at {}", Location::caller())); |
| 28 | + /// ``` |
| 29 | + /// Use instead: |
| 30 | + /// ```rust |
| 31 | + /// # use std::panic::Location; |
| 32 | + /// println!("error: something failed at {}", Location::caller()); |
| 33 | + /// ``` |
| 34 | + pub FORMAT_IN_FORMAT_ARGS, |
| 35 | + perf, |
| 36 | + "`format!` used in a macro that does formatting" |
| 37 | +} |
| 38 | + |
| 39 | +declare_clippy_lint! { |
| 40 | + /// ### What it does |
| 41 | + /// Checks for [`ToString::to_string`](https://doc.rust-lang.org/std/string/trait.ToString.html#tymethod.to_string) |
| 42 | + /// applied to a type that implements [`Display`](https://doc.rust-lang.org/std/fmt/trait.Display.html) |
| 43 | + /// in a macro that does formatting. |
| 44 | + /// |
| 45 | + /// ### Why is this bad? |
| 46 | + /// Since the type implements `Display`, the use of `to_string` is |
| 47 | + /// unnecessary. |
| 48 | + /// |
| 49 | + /// ### Example |
| 50 | + /// ```rust |
| 51 | + /// # use std::panic::Location; |
| 52 | + /// println!("error: something failed at {}", Location::caller().to_string()); |
| 53 | + /// ``` |
| 54 | + /// Use instead: |
| 55 | + /// ```rust |
| 56 | + /// # use std::panic::Location; |
| 57 | + /// println!("error: something failed at {}", Location::caller()); |
| 58 | + /// ``` |
| 59 | + pub TO_STRING_IN_FORMAT_ARGS, |
| 60 | + perf, |
| 61 | + "`to_string` applied to a type that implements `Display` in format args" |
| 62 | +} |
| 63 | + |
| 64 | +declare_lint_pass!(FormatArgs => [FORMAT_IN_FORMAT_ARGS, TO_STRING_IN_FORMAT_ARGS]); |
| 65 | + |
| 66 | +const FORMAT_MACRO_PATHS: &[&[&str]] = &[ |
| 67 | + &paths::FORMAT_ARGS_MACRO, |
| 68 | + &paths::ASSERT_EQ_MACRO, |
| 69 | + &paths::ASSERT_MACRO, |
| 70 | + &paths::ASSERT_NE_MACRO, |
| 71 | + &paths::EPRINT_MACRO, |
| 72 | + &paths::EPRINTLN_MACRO, |
| 73 | + &paths::PRINT_MACRO, |
| 74 | + &paths::PRINTLN_MACRO, |
| 75 | + &paths::WRITE_MACRO, |
| 76 | + &paths::WRITELN_MACRO, |
| 77 | +]; |
| 78 | + |
| 79 | +const FORMAT_MACRO_DIAG_ITEMS: &[Symbol] = &[sym::format_macro, sym::std_panic_macro]; |
| 80 | + |
| 81 | +impl<'tcx> LateLintPass<'tcx> for FormatArgs { |
| 82 | + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { |
| 83 | + if_chain! { |
| 84 | + if let Some(format_args) = FormatArgsExpn::parse(expr); |
| 85 | + let expr_expn_data = expr.span.ctxt().outer_expn_data(); |
| 86 | + let outermost_expn_data = outermost_expn_data(expr_expn_data); |
| 87 | + if let Some(macro_def_id) = outermost_expn_data.macro_def_id; |
| 88 | + if FORMAT_MACRO_PATHS |
| 89 | + .iter() |
| 90 | + .any(|path| match_def_path(cx, macro_def_id, path)) |
| 91 | + || FORMAT_MACRO_DIAG_ITEMS |
| 92 | + .iter() |
| 93 | + .any(|diag_item| cx.tcx.is_diagnostic_item(*diag_item, macro_def_id)); |
| 94 | + if let ExpnKind::Macro(_, name) = outermost_expn_data.kind; |
| 95 | + if let Some(args) = format_args.args(); |
| 96 | + then { |
| 97 | + for (i, arg) in args.iter().enumerate() { |
| 98 | + if !arg.is_display() { |
| 99 | + continue; |
| 100 | + } |
| 101 | + if arg.has_string_formatting() { |
| 102 | + continue; |
| 103 | + } |
| 104 | + if is_aliased(&args, i) { |
| 105 | + continue; |
| 106 | + } |
| 107 | + check_format_in_format_args(cx, outermost_expn_data.call_site, name, arg); |
| 108 | + check_to_string_in_format_args(cx, name, arg); |
| 109 | + } |
| 110 | + } |
| 111 | + } |
| 112 | + } |
| 113 | +} |
| 114 | + |
| 115 | +fn outermost_expn_data(expn_data: ExpnData) -> ExpnData { |
| 116 | + if expn_data.call_site.from_expansion() { |
| 117 | + outermost_expn_data(expn_data.call_site.ctxt().outer_expn_data()) |
| 118 | + } else { |
| 119 | + expn_data |
| 120 | + } |
| 121 | +} |
| 122 | + |
| 123 | +fn check_format_in_format_args(cx: &LateContext<'_>, call_site: Span, name: Symbol, arg: &FormatArgsArg<'_>) { |
| 124 | + if_chain! { |
| 125 | + if FormatExpn::parse(arg.value).is_some(); |
| 126 | + if !arg.value.span.ctxt().outer_expn_data().call_site.from_expansion(); |
| 127 | + then { |
| 128 | + span_lint_and_then( |
| 129 | + cx, |
| 130 | + FORMAT_IN_FORMAT_ARGS, |
| 131 | + trim_semicolon(cx, call_site), |
| 132 | + &format!("`format!` in `{}!` args", name), |
| 133 | + |diag| { |
| 134 | + diag.help(&format!( |
| 135 | + "combine the `format!(..)` arguments with the outer `{}!(..)` call", |
| 136 | + name |
| 137 | + )); |
| 138 | + diag.help("or consider changing `format!` to `format_args!`"); |
| 139 | + }, |
| 140 | + ); |
| 141 | + } |
| 142 | + } |
| 143 | +} |
| 144 | + |
| 145 | +fn check_to_string_in_format_args<'tcx>(cx: &LateContext<'tcx>, name: Symbol, arg: &FormatArgsArg<'tcx>) { |
| 146 | + let value = arg.value; |
| 147 | + if_chain! { |
| 148 | + if !value.span.from_expansion(); |
| 149 | + if let ExprKind::MethodCall(_, _, [receiver], _) = value.kind; |
| 150 | + if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(value.hir_id); |
| 151 | + if is_diag_trait_item(cx, method_def_id, sym::ToString); |
| 152 | + let receiver_ty = cx.typeck_results().expr_ty(receiver); |
| 153 | + if let Some(display_trait_id) = cx.tcx.get_diagnostic_item(sym::Display); |
| 154 | + if let Some(receiver_snippet) = snippet_opt(cx, receiver.span); |
| 155 | + then { |
| 156 | + let (n_needed_derefs, target) = count_needed_derefs( |
| 157 | + receiver_ty, |
| 158 | + cx.typeck_results().expr_adjustments(receiver).iter(), |
| 159 | + ); |
| 160 | + if implements_trait(cx, target, display_trait_id, &[]) { |
| 161 | + if n_needed_derefs == 0 { |
| 162 | + span_lint_and_sugg( |
| 163 | + cx, |
| 164 | + TO_STRING_IN_FORMAT_ARGS, |
| 165 | + value.span.with_lo(receiver.span.hi()), |
| 166 | + &format!("`to_string` applied to a type that implements `Display` in `{}!` args", name), |
| 167 | + "remove this", |
| 168 | + String::new(), |
| 169 | + Applicability::MachineApplicable, |
| 170 | + ); |
| 171 | + } else { |
| 172 | + span_lint_and_sugg( |
| 173 | + cx, |
| 174 | + TO_STRING_IN_FORMAT_ARGS, |
| 175 | + value.span, |
| 176 | + &format!("`to_string` applied to a type that implements `Display` in `{}!` args", name), |
| 177 | + "use this", |
| 178 | + format!("{:*>width$}{}", "", receiver_snippet, width = n_needed_derefs), |
| 179 | + Applicability::MachineApplicable, |
| 180 | + ); |
| 181 | + } |
| 182 | + } |
| 183 | + } |
| 184 | + } |
| 185 | +} |
| 186 | + |
| 187 | +// Returns true if `args[i]` "refers to" or "is referred to by" another argument. |
| 188 | +fn is_aliased(args: &[FormatArgsArg<'_>], i: usize) -> bool { |
| 189 | + let value = args[i].value; |
| 190 | + args.iter() |
| 191 | + .enumerate() |
| 192 | + .any(|(j, arg)| i != j && std::ptr::eq(value, arg.value)) |
| 193 | +} |
| 194 | + |
| 195 | +fn trim_semicolon(cx: &LateContext<'_>, span: Span) -> Span { |
| 196 | + snippet_opt(cx, span).map_or(span, |snippet| { |
| 197 | + let snippet = snippet.trim_end_matches(';'); |
| 198 | + span.with_hi(span.lo() + BytePos(u32::try_from(snippet.len()).unwrap())) |
| 199 | + }) |
| 200 | +} |
| 201 | + |
| 202 | +fn count_needed_derefs<'tcx, I>(mut ty: Ty<'tcx>, mut iter: I) -> (usize, Ty<'tcx>) |
| 203 | +where |
| 204 | + I: Iterator<Item = &'tcx Adjustment<'tcx>>, |
| 205 | +{ |
| 206 | + let mut n_total = 0; |
| 207 | + let mut n_needed = 0; |
| 208 | + loop { |
| 209 | + if let Some(Adjustment { |
| 210 | + kind: Adjust::Deref(overloaded_deref), |
| 211 | + target, |
| 212 | + }) = iter.next() |
| 213 | + { |
| 214 | + n_total += 1; |
| 215 | + if overloaded_deref.is_some() { |
| 216 | + n_needed = n_total; |
| 217 | + } |
| 218 | + ty = target; |
| 219 | + } else { |
| 220 | + return (n_needed, ty); |
| 221 | + } |
| 222 | + } |
| 223 | +} |
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