diff options
Diffstat (limited to 'clippy_lints/src/format_args.rs')
| -rw-r--r-- | clippy_lints/src/format_args.rs | 183 |
1 files changed, 149 insertions, 34 deletions
diff --git a/clippy_lints/src/format_args.rs b/clippy_lints/src/format_args.rs index 99bef62f814..4c4a1e06cd4 100644 --- a/clippy_lints/src/format_args.rs +++ b/clippy_lints/src/format_args.rs @@ -1,8 +1,10 @@ use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then}; use clippy_utils::macros::FormatParamKind::{Implicit, Named, Numbered, Starred}; -use clippy_utils::macros::{is_format_macro, FormatArgsExpn, FormatParam, FormatParamUsage}; +use clippy_utils::macros::{ + is_format_macro, is_panic, root_macro_call, Count, FormatArg, FormatArgsExpn, FormatParam, FormatParamUsage, +}; use clippy_utils::source::snippet_opt; -use clippy_utils::ty::implements_trait; +use clippy_utils::ty::{implements_trait, is_type_diagnostic_item}; use clippy_utils::{is_diag_trait_item, meets_msrv, msrvs}; use if_chain::if_chain; use itertools::Itertools; @@ -13,6 +15,8 @@ use rustc_middle::ty::adjustment::{Adjust, Adjustment}; use rustc_middle::ty::Ty; use rustc_semver::RustcVersion; use rustc_session::{declare_tool_lint, impl_lint_pass}; +use rustc_span::def_id::DefId; +use rustc_span::edition::Edition::Edition2021; use rustc_span::{sym, ExpnData, ExpnKind, Span, Symbol}; declare_clippy_lint! { @@ -111,11 +115,47 @@ declare_clippy_lint! { /// nothing will be suggested, e.g. `println!("{0}={1}", var, 1+2)`. #[clippy::version = "1.65.0"] pub UNINLINED_FORMAT_ARGS, - pedantic, + style, "using non-inlined variables in `format!` calls" } -impl_lint_pass!(FormatArgs => [FORMAT_IN_FORMAT_ARGS, UNINLINED_FORMAT_ARGS, TO_STRING_IN_FORMAT_ARGS]); +declare_clippy_lint! { + /// ### What it does + /// Detects [formatting parameters] that have no effect on the output of + /// `format!()`, `println!()` or similar macros. + /// + /// ### Why is this bad? + /// Shorter format specifiers are easier to read, it may also indicate that + /// an expected formatting operation such as adding padding isn't happening. + /// + /// ### Example + /// ```rust + /// println!("{:.}", 1.0); + /// + /// println!("not padded: {:5}", format_args!("...")); + /// ``` + /// Use instead: + /// ```rust + /// println!("{}", 1.0); + /// + /// println!("not padded: {}", format_args!("...")); + /// // OR + /// println!("padded: {:5}", format!("...")); + /// ``` + /// + /// [formatting parameters]: https://doc.rust-lang.org/std/fmt/index.html#formatting-parameters + #[clippy::version = "1.66.0"] + pub UNUSED_FORMAT_SPECS, + complexity, + "use of a format specifier that has no effect" +} + +impl_lint_pass!(FormatArgs => [ + FORMAT_IN_FORMAT_ARGS, + TO_STRING_IN_FORMAT_ARGS, + UNINLINED_FORMAT_ARGS, + UNUSED_FORMAT_SPECS, +]); pub struct FormatArgs { msrv: Option<RustcVersion>, @@ -130,27 +170,26 @@ impl FormatArgs { 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(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 is_format_macro(cx, macro_def_id); - if let ExpnKind::Macro(_, name) = outermost_expn_data.kind; - then { - for arg in &format_args.args { - if !arg.format.is_default() { - continue; - } - if is_aliased(&format_args, arg.param.value.hir_id) { - continue; - } - check_format_in_format_args(cx, outermost_expn_data.call_site, name, arg.param.value); - check_to_string_in_format_args(cx, name, arg.param.value); + 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) + && let Some(macro_def_id) = outermost_expn_data.macro_def_id + && is_format_macro(cx, macro_def_id) + && let ExpnKind::Macro(_, name) = outermost_expn_data.kind + { + for arg in &format_args.args { + check_unused_format_specifier(cx, arg); + if !arg.format.is_default() { + continue; } - if meets_msrv(self.msrv, msrvs::FORMAT_ARGS_CAPTURE) { - check_uninlined_args(cx, &format_args, outermost_expn_data.call_site); + if is_aliased(&format_args, arg.param.value.hir_id) { + continue; } + check_format_in_format_args(cx, outermost_expn_data.call_site, name, arg.param.value); + check_to_string_in_format_args(cx, name, arg.param.value); + } + if meets_msrv(self.msrv, msrvs::FORMAT_ARGS_CAPTURE) { + check_uninlined_args(cx, &format_args, outermost_expn_data.call_site, macro_def_id); } } } @@ -158,10 +197,84 @@ impl<'tcx> LateLintPass<'tcx> for FormatArgs { extract_msrv_attr!(LateContext); } -fn check_uninlined_args(cx: &LateContext<'_>, args: &FormatArgsExpn<'_>, call_site: Span) { +fn check_unused_format_specifier(cx: &LateContext<'_>, arg: &FormatArg<'_>) { + let param_ty = cx.typeck_results().expr_ty(arg.param.value).peel_refs(); + + if let Count::Implied(Some(mut span)) = arg.format.precision + && !span.is_empty() + { + span_lint_and_then( + cx, + UNUSED_FORMAT_SPECS, + span, + "empty precision specifier has no effect", + |diag| { + if param_ty.is_floating_point() { + diag.note("a precision specifier is not required to format floats"); + } + + if arg.format.is_default() { + // If there's no other specifiers remove the `:` too + span = arg.format_span(); + } + + diag.span_suggestion_verbose(span, "remove the `.`", "", Applicability::MachineApplicable); + }, + ); + } + + if is_type_diagnostic_item(cx, param_ty, sym::Arguments) && !arg.format.is_default_for_trait() { + span_lint_and_then( + cx, + UNUSED_FORMAT_SPECS, + arg.span, + "format specifiers have no effect on `format_args!()`", + |diag| { + let mut suggest_format = |spec, span| { + let message = format!("for the {spec} to apply consider using `format!()`"); + + if let Some(mac_call) = root_macro_call(arg.param.value.span) + && cx.tcx.is_diagnostic_item(sym::format_args_macro, mac_call.def_id) + && arg.span.eq_ctxt(mac_call.span) + { + diag.span_suggestion( + cx.sess().source_map().span_until_char(mac_call.span, '!'), + message, + "format", + Applicability::MaybeIncorrect, + ); + } else if let Some(span) = span { + diag.span_help(span, message); + } + }; + + if !arg.format.width.is_implied() { + suggest_format("width", arg.format.width.span()); + } + + if !arg.format.precision.is_implied() { + suggest_format("precision", arg.format.precision.span()); + } + + diag.span_suggestion_verbose( + arg.format_span(), + "if the current behavior is intentional, remove the format specifiers", + "", + Applicability::MaybeIncorrect, + ); + }, + ); + } +} + +fn check_uninlined_args(cx: &LateContext<'_>, args: &FormatArgsExpn<'_>, call_site: Span, def_id: DefId) { if args.format_string.span.from_expansion() { return; } + if call_site.edition() < Edition2021 && is_panic(cx, def_id) { + // panic! before 2021 edition considers a single string argument as non-format + return; + } let mut fixes = Vec::new(); // If any of the arguments are referenced by an index number, @@ -217,12 +330,7 @@ fn outermost_expn_data(expn_data: ExpnData) -> ExpnData { } } -fn check_format_in_format_args( - cx: &LateContext<'_>, - call_site: Span, - name: Symbol, - arg: &Expr<'_>, -) { +fn check_format_in_format_args(cx: &LateContext<'_>, call_site: Span, name: Symbol, arg: &Expr<'_>) { let expn_data = arg.span.ctxt().outer_expn_data(); if expn_data.call_site.from_expansion() { return; @@ -248,7 +356,7 @@ fn check_format_in_format_args( fn check_to_string_in_format_args(cx: &LateContext<'_>, name: Symbol, value: &Expr<'_>) { if_chain! { if !value.span.from_expansion(); - if let ExprKind::MethodCall(_, receiver, [], _) = value.kind; + if let ExprKind::MethodCall(_, receiver, [], to_string_span) = 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); @@ -264,7 +372,7 @@ fn check_to_string_in_format_args(cx: &LateContext<'_>, name: Symbol, value: &Ex span_lint_and_sugg( cx, TO_STRING_IN_FORMAT_ARGS, - value.span.with_lo(receiver.span.hi()), + to_string_span.with_lo(receiver.span.hi()), &format!( "`to_string` applied to a type that implements `Display` in `{name}!` args" ), @@ -295,7 +403,10 @@ fn check_to_string_in_format_args(cx: &LateContext<'_>, name: Symbol, value: &Ex /// Returns true if `hir_id` is referred to by multiple format params fn is_aliased(args: &FormatArgsExpn<'_>, hir_id: HirId) -> bool { - args.params().filter(|param| param.value.hir_id == hir_id).at_most_one().is_err() + args.params() + .filter(|param| param.value.hir_id == hir_id) + .at_most_one() + .is_err() } fn count_needed_derefs<'tcx, I>(mut ty: Ty<'tcx>, mut iter: I) -> (usize, Ty<'tcx>) @@ -305,7 +416,11 @@ where let mut n_total = 0; let mut n_needed = 0; loop { - if let Some(Adjustment { kind: Adjust::Deref(overloaded_deref), target }) = iter.next() { + if let Some(Adjustment { + kind: Adjust::Deref(overloaded_deref), + target, + }) = iter.next() + { n_total += 1; if overloaded_deref.is_some() { n_needed = n_total; |