use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
-use clippy_utils::is_diag_trait_item;
-use clippy_utils::macros::{is_format_macro, FormatArgsExpn};
+use clippy_utils::macros::FormatParamKind::{Implicit, Named, Numbered, Starred};
+use clippy_utils::macros::{is_format_macro, FormatArgsExpn, FormatParam, FormatParamUsage};
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::implements_trait;
+use clippy_utils::{is_diag_trait_item, meets_msrv, msrvs};
use if_chain::if_chain;
use itertools::Itertools;
use rustc_errors::Applicability;
-use rustc_hir::{Expr, ExprKind, HirId};
-use rustc_lint::{LateContext, LateLintPass};
+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_session::{declare_lint_pass, declare_tool_lint};
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::{sym, ExpnData, ExpnKind, Span, Symbol};
declare_clippy_lint! {
"`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]);
+declare_clippy_lint! {
+ /// ### What it does
+ /// Detect when a variable is not inlined in a format string,
+ /// and suggests to inline it.
+ ///
+ /// ### Why is this bad?
+ /// Non-inlined code is slightly more difficult to read and understand,
+ /// as it requires arguments to be matched against the format string.
+ /// The inlined syntax, where allowed, is simpler.
+ ///
+ /// ### Example
+ /// ```rust
+ /// # let var = 42;
+ /// # let width = 1;
+ /// # let prec = 2;
+ /// format!("{}", var);
+ /// format!("{v:?}", v = var);
+ /// format!("{0} {0}", var);
+ /// format!("{0:1$}", var, width);
+ /// format!("{:.*}", prec, var);
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// # let var = 42;
+ /// # let width = 1;
+ /// # let prec = 2;
+ /// format!("{var}");
+ /// format!("{var:?}");
+ /// format!("{var} {var}");
+ /// format!("{var:width$}");
+ /// format!("{var:.prec$}");
+ /// ```
+ ///
+ /// ### Known Problems
+ ///
+ /// There may be a false positive if the format string is expanded from certain proc macros:
+ ///
+ /// ```ignore
+ /// println!(indoc!("{}"), var);
+ /// ```
+ ///
+ /// If a format string contains a numbered argument that cannot be inlined
+ /// nothing will be suggested, e.g. `println!("{0}={1}", var, 1+2)`.
+ #[clippy::version = "1.65.0"]
+ pub UNINLINED_FORMAT_ARGS,
+ pedantic,
+ "using non-inlined variables in `format!` calls"
+}
+
+impl_lint_pass!(FormatArgs => [FORMAT_IN_FORMAT_ARGS, UNINLINED_FORMAT_ARGS, TO_STRING_IN_FORMAT_ARGS]);
+
+pub struct FormatArgs {
+ msrv: Option<RustcVersion>,
+}
+
+impl FormatArgs {
+ #[must_use]
+ pub fn new(msrv: Option<RustcVersion>) -> Self {
+ Self { msrv }
+ }
+}
impl<'tcx> LateLintPass<'tcx> for FormatArgs {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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);
+ }
}
}
}
+
+ extract_msrv_attr!(LateContext);
+}
+
+fn check_uninlined_args(cx: &LateContext<'_>, args: &FormatArgsExpn<'_>, call_site: Span) {
+ if args.format_string.span.from_expansion() {
+ return;
+ }
+
+ let mut fixes = Vec::new();
+ // If any of the arguments are referenced by an index number,
+ // and that argument is not a simple variable and cannot be inlined,
+ // we cannot remove any other arguments in the format string,
+ // because the index numbers might be wrong after inlining.
+ // Example of an un-inlinable format: print!("{}{1}", foo, 2)
+ if !args.params().all(|p| check_one_arg(args, &p, &mut fixes)) || fixes.is_empty() {
+ 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;
+ }
+
+ span_lint_and_then(
+ cx,
+ UNINLINED_FORMAT_ARGS,
+ call_site,
+ "variables can be used directly in the `format!` string",
+ |diag| {
+ diag.multipart_suggestion("change this to", fixes, Applicability::MachineApplicable);
+ },
+ );
+}
+
+fn check_one_arg(args: &FormatArgsExpn<'_>, param: &FormatParam<'_>, fixes: &mut Vec<(Span, String)>) -> bool {
+ if matches!(param.kind, Implicit | Starred | Named(_) | Numbered)
+ && let ExprKind::Path(QPath::Resolved(None, path)) = param.value.kind
+ && let [segment] = path.segments
+ && let Some(arg_span) = args.value_with_prev_comma_span(param.value.hir_id)
+ {
+ let replacement = match param.usage {
+ FormatParamUsage::Argument => segment.ident.name.to_string(),
+ FormatParamUsage::Width => format!("{}$", segment.ident.name),
+ FormatParamUsage::Precision => format!(".{}$", segment.ident.name),
+ };
+ fixes.push((param.span, replacement));
+ fixes.push((arg_span, String::new()));
+ true // successful inlining, continue checking
+ } else {
+ // if we can't inline a numbered argument, we can't continue
+ param.kind != Numbered
+ }
}
fn outermost_expn_data(expn_data: ExpnData) -> ExpnData {
cx,
FORMAT_IN_FORMAT_ARGS,
call_site,
- &format!("`format!` in `{}!` args", name),
+ &format!("`format!` in `{name}!` args"),
|diag| {
diag.help(&format!(
- "combine the `format!(..)` arguments with the outer `{}!(..)` call",
- name
+ "combine the `format!(..)` arguments with the outer `{name}!(..)` call"
));
diag.help("or consider changing `format!` to `format_args!`");
},
TO_STRING_IN_FORMAT_ARGS,
value.span.with_lo(receiver.span.hi()),
&format!(
- "`to_string` applied to a type that implements `Display` in `{}!` args",
- name
+ "`to_string` applied to a type that implements `Display` in `{name}!` args"
),
"remove this",
String::new(),
TO_STRING_IN_FORMAT_ARGS,
value.span,
&format!(
- "`to_string` applied to a type that implements `Display` in `{}!` args",
- name
+ "`to_string` applied to a type that implements `Display` in `{name}!` args"
),
"use this",
format!(
- "{}{:*>width$}{}",
+ "{}{:*>n_needed_derefs$}{receiver_snippet}",
if needs_ref { "&" } else { "" },
- "",
- receiver_snippet,
- width = n_needed_derefs
+ ""
),
Applicability::MachineApplicable,
);
}
}
-// Returns true if `hir_id` is referred to by multiple format params
+/// 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()
}
projects / rust.git / blobdiff