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Migrate format_args.rs to rustc_ast::FormatArgs
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No longer lints empty precisions `{:.}` as the spans aren't available
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@Alexendoo
Alexendoo committed Mar 28, 2023
1 parent 70db226 commit 066949c
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Showing 11 changed files with 265 additions and 239 deletions.
1 change: 1 addition & 0 deletions clippy_lints/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ keywords = ["clippy", "lint", "plugin"]
edition = "2021"

[dependencies]
arrayvec = { version = "0.7", default-features = false }
cargo_metadata = "0.15.3"
clippy_utils = { path = "../clippy_utils" }
declare_clippy_lint = { path = "../declare_clippy_lint" }
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211 changes: 125 additions & 86 deletions clippy_lints/src/format_args.rs
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Original file line number Diff line number Diff line change
@@ -1,27 +1,31 @@
use arrayvec::ArrayVec;
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, NamedInline, Numbered, Starred};
use clippy_utils::macros::{
is_assert_macro, is_format_macro, is_panic, root_macro_call, Count, FormatArg, FormatArgsExpn, FormatParam,
FormatParamUsage,
find_format_arg_expr, find_format_args, format_arg_removal_span, format_placeholder_format_span, is_assert_macro,
is_format_macro, is_panic, root_macro_call, root_macro_call_first_node, FormatParamUsage,
};
use clippy_utils::msrvs::{self, Msrv};
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::{implements_trait, is_type_lang_item};
use if_chain::if_chain;
use itertools::Itertools;
use rustc_ast::{
FormatArgPosition, FormatArgPositionKind, FormatArgsPiece, FormatArgumentKind, FormatCount, FormatOptions,
FormatPlaceholder, FormatTrait,
};
use rustc_errors::{
Applicability,
SuggestionStyle::{CompletelyHidden, ShowCode},
};
use rustc_hir::{Expr, ExprKind, HirId, LangItem, QPath};
use rustc_hir::{Expr, ExprKind, LangItem};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::ty::adjustment::{Adjust, Adjustment};
use rustc_middle::ty::Ty;
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};
use rustc_span::{sym, Span, Symbol};

declare_clippy_lint! {
/// ### What it does
Expand Down Expand Up @@ -184,111 +188,121 @@ impl FormatArgs {

impl<'tcx> LateLintPass<'tcx> for FormatArgs {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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 is_aliased(&format_args, arg.param.value.hir_id) {
continue;
let Some(macro_call) = root_macro_call_first_node(cx, expr) else { return };
if !is_format_macro(cx, macro_call.def_id) {
return;
}
let name = cx.tcx.item_name(macro_call.def_id);

find_format_args(cx, expr, macro_call.expn, |format_args| {
for piece in &format_args.template {
if let FormatArgsPiece::Placeholder(placeholder) = piece
&& let Ok(index) = placeholder.argument.index
&& let Some(arg) = format_args.arguments.all_args().get(index)
{
let arg_expr = find_format_arg_expr(expr, arg);

check_unused_format_specifier(cx, placeholder, arg_expr);

if placeholder.format_trait != FormatTrait::Display
|| placeholder.format_options != FormatOptions::default()
|| is_aliased(format_args, index)
{
continue;
}

if let Ok(arg_hir_expr) = arg_expr {
check_format_in_format_args(cx, macro_call.span, name, arg_hir_expr);
check_to_string_in_format_args(cx, name, arg_hir_expr);
}
}
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, self.ignore_mixed);
check_uninlined_args(cx, &format_args, macro_call.span, macro_call.def_id, self.ignore_mixed);
}
}
});
}

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();
fn check_unused_format_specifier(
cx: &LateContext<'_>,
placeholder: &FormatPlaceholder,
arg_expr: Result<&Expr<'_>, &rustc_ast::Expr>,
) {
let ty_or_ast_expr = arg_expr.map(|expr| cx.typeck_results().expr_ty(expr).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");
}
let is_format_args = match ty_or_ast_expr {
Ok(ty) => is_type_lang_item(cx, ty, LangItem::FormatArguments),
// TODO: Change to .peel_parens_and_refs() after https://github.com/rust-lang/rust/pull/106824
Err(expr) => matches!(expr.peel_parens().kind, rustc_ast::ExprKind::FormatArgs(_)),
};

if arg.format.is_default() {
// If there's no other specifiers remove the `:` too
span = arg.format_span();
}
let options = &placeholder.format_options;

diag.span_suggestion_verbose(span, "remove the `.`", "", Applicability::MachineApplicable);
},
);
}
let arg_span = match arg_expr {
Ok(expr) => expr.span,
Err(expr) => expr.span,
};

if is_type_lang_item(cx, param_ty, LangItem::FormatArguments) && !arg.format.is_default_for_trait() {
if let Some(placeholder_span) = placeholder.span
&& is_format_args
&& *options != FormatOptions::default()
{
span_lint_and_then(
cx,
UNUSED_FORMAT_SPECS,
arg.span,
placeholder_span,
"format specifiers have no effect on `format_args!()`",
|diag| {
let mut suggest_format = |spec, span| {
let mut suggest_format = |spec| {
let message = format!("for the {spec} to apply consider using `format!()`");

if let Some(mac_call) = root_macro_call(arg.param.value.span)
if let Some(mac_call) = root_macro_call(arg_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);
} else {
diag.help(message);
}
};

if !arg.format.width.is_implied() {
suggest_format("width", arg.format.width.span());
if options.width.is_some() {
suggest_format("width");
}

if !arg.format.precision.is_implied() {
suggest_format("precision", arg.format.precision.span());
if options.precision.is_some() {
suggest_format("precision");
}

diag.span_suggestion_verbose(
arg.format_span(),
"if the current behavior is intentional, remove the format specifiers",
"",
Applicability::MaybeIncorrect,
);
if let Some(format_span) = format_placeholder_format_span(placeholder) {
diag.span_suggestion_verbose(
format_span,
"if the current behavior is intentional, remove the format specifiers",
"",
Applicability::MaybeIncorrect,
);
}
},
);
}
}

fn check_uninlined_args(
cx: &LateContext<'_>,
args: &FormatArgsExpn<'_>,
args: &rustc_ast::FormatArgs,
call_site: Span,
def_id: DefId,
ignore_mixed: bool,
) {
if args.format_string.span.from_expansion() {
if args.span.from_expansion() {
return;
}
if call_site.edition() < Edition2021 && (is_panic(cx, def_id) || is_assert_macro(cx, def_id)) {
Expand All @@ -303,7 +317,13 @@ fn check_uninlined_args(
// 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, ignore_mixed)) || fixes.is_empty() {
for (pos, usage) in format_arg_positions(args) {
if !check_one_arg(args, pos, usage, &mut fixes, ignore_mixed) {
return;
}
}

if fixes.is_empty() {
return;
}

Expand Down Expand Up @@ -332,38 +352,36 @@ fn check_uninlined_args(
}

fn check_one_arg(
args: &FormatArgsExpn<'_>,
param: &FormatParam<'_>,
args: &rustc_ast::FormatArgs,
pos: &FormatArgPosition,
usage: FormatParamUsage,
fixes: &mut Vec<(Span, String)>,
ignore_mixed: bool,
) -> bool {
if matches!(param.kind, Implicit | Starred | Named(_) | Numbered)
&& let ExprKind::Path(QPath::Resolved(None, path)) = param.value.kind
&& let [segment] = path.segments
let index = pos.index.unwrap();
let arg = &args.arguments.all_args()[index];

if !matches!(arg.kind, FormatArgumentKind::Captured(_))
&& let rustc_ast::ExprKind::Path(None, path) = &arg.expr.kind
&& let [segment] = path.segments.as_slice()
&& segment.args.is_none()
&& let Some(arg_span) = args.value_with_prev_comma_span(param.value.hir_id)
&& let Some(arg_span) = format_arg_removal_span(args, index)
&& let Some(pos_span) = pos.span
{
let replacement = match param.usage {
let replacement = match 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((pos_span, replacement));
fixes.push((arg_span, String::new()));
true // successful inlining, continue checking
} else {
// Do not continue inlining (return false) in case
// * if we can't inline a numbered argument, e.g. `print!("{0} ...", foo.bar, ...)`
// * if allow_mixed_uninlined_format_args is false and this arg hasn't been inlined already
param.kind != Numbered && (!ignore_mixed || matches!(param.kind, NamedInline(_)))
}
}

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
pos.kind != FormatArgPositionKind::Number
&& (!ignore_mixed || matches!(arg.kind, FormatArgumentKind::Captured(_)))
}
}

Expand Down Expand Up @@ -438,10 +456,31 @@ 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)
fn format_arg_positions(
format_args: &rustc_ast::FormatArgs,
) -> impl Iterator<Item = (&FormatArgPosition, FormatParamUsage)> {
format_args.template.iter().flat_map(|piece| match piece {
FormatArgsPiece::Placeholder(placeholder) => {
let mut positions = ArrayVec::<_, 3>::new();

positions.push((&placeholder.argument, FormatParamUsage::Argument));
if let Some(FormatCount::Argument(position)) = &placeholder.format_options.width {
positions.push((position, FormatParamUsage::Width));
}
if let Some(FormatCount::Argument(position)) = &placeholder.format_options.precision {
positions.push((position, FormatParamUsage::Precision));
}

positions
},
FormatArgsPiece::Literal(_) => ArrayVec::new(),
})
}

/// Returns true if the format argument at `index` is referred to by multiple format params
fn is_aliased(format_args: &rustc_ast::FormatArgs, index: usize) -> bool {
format_arg_positions(format_args)
.filter(|(position, _)| position.index == Ok(index))
.at_most_one()
.is_err()
}
Expand Down
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