use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
+use clippy_utils::is_diag_trait_item;
use clippy_utils::macros::FormatParamKind::{Implicit, Named, Numbered, Starred};
-use clippy_utils::macros::{is_format_macro, is_panic, FormatArgsExpn, FormatParam, FormatParamUsage};
+use clippy_utils::macros::{
+ is_format_macro, is_panic, root_macro_call, Count, FormatArg, FormatArgsExpn, FormatParam, FormatParamUsage,
+};
+use clippy_utils::msrvs::{self, Msrv};
use clippy_utils::source::snippet_opt;
-use clippy_utils::ty::implements_trait;
-use clippy_utils::{is_diag_trait_item, meets_msrv, msrvs};
+use clippy_utils::ty::{implements_trait, is_type_diagnostic_item};
use if_chain::if_chain;
use itertools::Itertools;
-use rustc_errors::Applicability;
+use rustc_errors::{
+ Applicability,
+ SuggestionStyle::{CompletelyHidden, ShowCode},
+};
use rustc_hir::{Expr, ExprKind, HirId, QPath};
use rustc_lint::{LateContext, LateLintPass, LintContext};
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;
"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>,
+ msrv: Msrv,
}
impl FormatArgs {
#[must_use]
- pub fn new(msrv: Option<RustcVersion>) -> Self {
+ pub fn new(msrv: Msrv) -> Self {
Self { msrv }
}
}
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, macro_def_id);
+ 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 self.msrv.meets(msrvs::FORMAT_ARGS_CAPTURE) {
+ check_uninlined_args(cx, &format_args, outermost_expn_data.call_site, macro_def_id);
}
}
}
extract_msrv_attr!(LateContext);
}
+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;
return;
}
- // Temporarily ignore multiline spans: https://github.com/rust-lang/rust/pull/102729#discussion_r988704308
- if fixes.iter().any(|(span, _)| cx.sess().source_map().is_multiline(*span)) {
- return;
- }
+ // multiline span display suggestion is sometimes broken: https://github.com/rust-lang/rust/pull/102729#discussion_r988704308
+ // in those cases, make the code suggestion hidden
+ let multiline_fix = fixes.iter().any(|(span, _)| cx.sess().source_map().is_multiline(*span));
span_lint_and_then(
cx,
call_site,
"variables can be used directly in the `format!` string",
|diag| {
- diag.multipart_suggestion("change this to", fixes, Applicability::MachineApplicable);
+ diag.multipart_suggestion_with_style(
+ "change this to",
+ fixes,
+ Applicability::MachineApplicable,
+ if multiline_fix { CompletelyHidden } else { ShowCode },
+ );
},
);
}
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);
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"
),
projects / rust.git / blobdiff