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Improve position named arguments lint underline and formatting names
For named arguments used as implicit position arguments, underline both the opening curly brace and either: * if there is formatting, the next character (which will either be the closing curl brace or the `:` denoting the start of formatting args) * if there is no formatting, the entire arg span (important if there is whitespace like `{ }`) This should make it more obvious where the named argument should be. Additionally, in the lint message, emit the formatting argument names without a dollar sign to avoid potentially confusion. Fixes #99907
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8 files changed

+305
-136
lines changed

8 files changed

+305
-136
lines changed

‎compiler/rustc_builtin_macros/src/format.rs

+61-25
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,7 @@ use smallvec::SmallVec;
1616

1717
use rustc_lint_defs::builtin::NAMED_ARGUMENTS_USED_POSITIONALLY;
1818
use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiagnostics, LintId};
19+
use rustc_parse_format::Count;
1920
use std::borrow::Cow;
2021
use std::collections::hash_map::Entry;
2122

@@ -57,26 +58,47 @@ struct PositionalNamedArg {
5758
replacement: Symbol,
5859
/// The span for the positional named argument (so the lint can point a message to it)
5960
positional_named_arg_span: Span,
61+
has_formatting: bool,
6062
}
6163

6264
impl PositionalNamedArg {
63-
/// Determines what span to replace with the name of the named argument
64-
fn get_span_to_replace(&self, cx: &Context<'_, '_>) -> Option<Span> {
65+
/// Determines:
66+
/// 1) span to be replaced with the name of the named argument and
67+
/// 2) span to be underlined for error messages
68+
fn get_positional_arg_spans(&self, cx: &Context<'_, '_>) -> (Option<Span>, Option<Span>) {
6569
if let Some(inner_span) = &self.inner_span_to_replace {
66-
return Some(
67-
cx.fmtsp.from_inner(InnerSpan { start: inner_span.start, end: inner_span.end }),
68-
);
70+
let span =
71+
cx.fmtsp.from_inner(InnerSpan { start: inner_span.start, end: inner_span.end });
72+
(Some(span), Some(span))
6973
} else if self.ty == PositionalNamedArgType::Arg {
70-
// In the case of a named argument whose position is implicit, there will not be a span
71-
// to replace. Instead, we insert the name after the `{`, which is the first character
72-
// of arg_span.
73-
return cx
74-
.arg_spans
75-
.get(self.cur_piece)
76-
.map(|arg_span| arg_span.with_lo(arg_span.lo() + BytePos(1)).shrink_to_lo());
74+
// In the case of a named argument whose position is implicit, if the argument *has*
75+
// formatting, there will not be a span to replace. Instead, we insert the name after
76+
// the `{`, which will be the first character of arg_span. If the argument does *not*
77+
// have formatting, there may or may not be a span to replace. This is because
78+
// whitespace is allowed in arguments without formatting (such as `format!("{ }", 1);`)
79+
// but is not allowed in arguments with formatting (an error will be generated in cases
80+
// like `format!("{ :1.1}", 1.0f32);`.
81+
// For the message span, if there is formatting, we want to use the opening `{` and the
82+
// next character, which will the `:` indicating the start of formatting. If there is
83+
// not any formatting, we want to underline the entire span.
84+
if self.has_formatting {
85+
cx.arg_spans.get(self.cur_piece).map_or((None, None), |arg_span| {
86+
(
87+
Some(arg_span.with_lo(arg_span.lo() + BytePos(1)).shrink_to_lo()),
88+
Some(arg_span.with_hi(arg_span.lo() + BytePos(2))),
89+
)
90+
})
91+
} else {
92+
cx.arg_spans.get(self.cur_piece).map_or((None, None), |arg_span| {
93+
let replace_start = arg_span.lo() + BytePos(1);
94+
let replace_end = arg_span.hi() - BytePos(1);
95+
let to_replace = arg_span.with_lo(replace_start).with_hi(replace_end);
96+
(Some(to_replace), Some(*arg_span))
97+
})
98+
}
99+
} else {
100+
(None, None)
77101
}
78-
79-
None
80102
}
81103
}
82104

@@ -117,10 +139,18 @@ impl PositionalNamedArgsLint {
117139
cur_piece: usize,
118140
inner_span_to_replace: Option<rustc_parse_format::InnerSpan>,
119141
names: &FxHashMap<Symbol, (usize, Span)>,
142+
has_formatting: bool,
120143
) {
121144
let start_of_named_args = total_args_length - names.len();
122145
if current_positional_arg >= start_of_named_args {
123-
self.maybe_push(format_argument_index, ty, cur_piece, inner_span_to_replace, names)
146+
self.maybe_push(
147+
format_argument_index,
148+
ty,
149+
cur_piece,
150+
inner_span_to_replace,
151+
names,
152+
has_formatting,
153+
)
124154
}
125155
}
126156

@@ -134,6 +164,7 @@ impl PositionalNamedArgsLint {
134164
cur_piece: usize,
135165
inner_span_to_replace: Option<rustc_parse_format::InnerSpan>,
136166
names: &FxHashMap<Symbol, (usize, Span)>,
167+
has_formatting: bool,
137168
) {
138169
let named_arg = names
139170
.iter()
@@ -156,6 +187,7 @@ impl PositionalNamedArgsLint {
156187
inner_span_to_replace,
157188
replacement,
158189
positional_named_arg_span,
190+
has_formatting,
159191
});
160192
}
161193
}
@@ -414,6 +446,9 @@ impl<'a, 'b> Context<'a, 'b> {
414446
PositionalNamedArgType::Precision,
415447
);
416448

449+
let has_precision = arg.format.precision != Count::CountImplied;
450+
let has_width = arg.format.width != Count::CountImplied;
451+
417452
// argument second, if it's an implicit positional parameter
418453
// it's written second, so it should come after width/precision.
419454
let pos = match arg.position {
@@ -426,6 +461,7 @@ impl<'a, 'b> Context<'a, 'b> {
426461
self.curpiece,
427462
arg_end,
428463
&self.names,
464+
has_precision || has_width,
429465
);
430466

431467
Exact(i)
@@ -439,6 +475,7 @@ impl<'a, 'b> Context<'a, 'b> {
439475
self.curpiece,
440476
None,
441477
&self.names,
478+
has_precision || has_width,
442479
);
443480
Exact(i)
444481
}
@@ -529,6 +566,7 @@ impl<'a, 'b> Context<'a, 'b> {
529566
self.curpiece,
530567
*inner_span,
531568
&self.names,
569+
true,
532570
);
533571
self.verify_arg_type(Exact(i), Count);
534572
}
@@ -1150,24 +1188,22 @@ pub fn expand_format_args_nl<'cx>(
11501188

11511189
fn create_lints_for_named_arguments_used_positionally(cx: &mut Context<'_, '_>) {
11521190
for named_arg in &cx.unused_names_lint.positional_named_args {
1153-
let arg_span = named_arg.get_span_to_replace(cx);
1191+
let (position_sp_to_replace, position_sp_for_msg) = named_arg.get_positional_arg_spans(cx);
11541192

11551193
let msg = format!("named argument `{}` is not used by name", named_arg.replacement);
1156-
let replacement = match named_arg.ty {
1157-
PositionalNamedArgType::Arg => named_arg.replacement.to_string(),
1158-
_ => named_arg.replacement.to_string() + "$",
1159-
};
11601194

11611195
cx.ecx.buffered_early_lint.push(BufferedEarlyLint {
11621196
span: MultiSpan::from_span(named_arg.positional_named_arg_span),
11631197
msg: msg.clone(),
11641198
node_id: ast::CRATE_NODE_ID,
11651199
lint_id: LintId::of(&NAMED_ARGUMENTS_USED_POSITIONALLY),
1166-
diagnostic: BuiltinLintDiagnostics::NamedArgumentUsedPositionally(
1167-
arg_span,
1168-
named_arg.positional_named_arg_span,
1169-
replacement,
1170-
),
1200+
diagnostic: BuiltinLintDiagnostics::NamedArgumentUsedPositionally {
1201+
position_sp_to_replace,
1202+
position_sp_for_msg,
1203+
named_arg_sp: named_arg.positional_named_arg_span,
1204+
named_arg_name: named_arg.replacement.to_string(),
1205+
is_formatting_arg: named_arg.ty != PositionalNamedArgType::Arg,
1206+
},
11711207
});
11721208
}
11731209
}

‎compiler/rustc_lint/src/context.rs

+11-6
Original file line numberDiff line numberDiff line change
@@ -856,13 +856,18 @@ pub trait LintContext: Sized {
856856
Applicability::MachineApplicable,
857857
);
858858
},
859-
BuiltinLintDiagnostics::NamedArgumentUsedPositionally(positional_arg, named_arg, name) => {
860-
db.span_label(named_arg, "this named argument is only referred to by position in formatting string");
861-
if let Some(positional_arg) = positional_arg {
862-
let msg = format!("this formatting argument uses named argument `{}` by position", name);
863-
db.span_label(positional_arg, msg);
859+
BuiltinLintDiagnostics::NamedArgumentUsedPositionally{ position_sp_to_replace, position_sp_for_msg, named_arg_sp, named_arg_name, is_formatting_arg} => {
860+
db.span_label(named_arg_sp, "this named argument is referred to by position in formatting string");
861+
if let Some(positional_arg_for_msg) = position_sp_for_msg {
862+
let msg = format!("this formatting argument uses named argument `{}` by position", named_arg_name);
863+
db.span_label(positional_arg_for_msg, msg);
864+
}
865+
866+
if let Some(positional_arg_to_replace) = position_sp_to_replace {
867+
let name = if is_formatting_arg { named_arg_name + "$" } else { named_arg_name };
868+
864869
db.span_suggestion_verbose(
865-
positional_arg,
870+
positional_arg_to_replace,
866871
"use the named argument by name to avoid ambiguity",
867872
name,
868873
Applicability::MaybeIncorrect,

‎compiler/rustc_lint_defs/src/lib.rs

+13-1
Original file line numberDiff line numberDiff line change
@@ -467,7 +467,19 @@ pub enum BuiltinLintDiagnostics {
467467
/// If true, the lifetime will be fully elided.
468468
use_span: Option<(Span, bool)>,
469469
},
470-
NamedArgumentUsedPositionally(Option<Span>, Span, String),
470+
NamedArgumentUsedPositionally {
471+
/// Span where the named argument is used by position and will be replaced with the named
472+
/// argument name
473+
position_sp_to_replace: Option<Span>,
474+
/// Span where the named argument is used by position and is used for lint messages
475+
position_sp_for_msg: Option<Span>,
476+
/// Span where the named argument's name is (so we know where to put the warning message)
477+
named_arg_sp: Span,
478+
/// String containing the named arguments name
479+
named_arg_name: String,
480+
/// Indicates if the named argument is used as a width/precision for formatting
481+
is_formatting_arg: bool,
482+
},
471483
}
472484

473485
/// Lints that are buffered up early on in the `Session` before the

‎src/test/ui/macros/issue-98466.stderr

+18-18
Original file line numberDiff line numberDiff line change
@@ -2,9 +2,9 @@ warning: named argument `_x` is not used by name
22
--> $DIR/issue-98466.rs:7:26
33
|
44
LL | println!("_x is {}", _x = 5);
5-
| - ^^ this named argument is only referred to by position in formatting string
6-
| |
7-
| this formatting argument uses named argument `_x` by position
5+
| -- ^^ this named argument is referred to by position in formatting string
6+
| |
7+
| this formatting argument uses named argument `_x` by position
88
|
99
= note: `#[warn(named_arguments_used_positionally)]` on by default
1010
help: use the named argument by name to avoid ambiguity
@@ -16,9 +16,9 @@ warning: named argument `y` is not used by name
1616
--> $DIR/issue-98466.rs:10:26
1717
|
1818
LL | println!("_x is {}", y = _x);
19-
| - ^ this named argument is only referred to by position in formatting string
20-
| |
21-
| this formatting argument uses named argument `y` by position
19+
| -- ^ this named argument is referred to by position in formatting string
20+
| |
21+
| this formatting argument uses named argument `y` by position
2222
|
2323
help: use the named argument by name to avoid ambiguity
2424
|
@@ -29,9 +29,9 @@ warning: named argument `y` is not used by name
2929
--> $DIR/issue-98466.rs:13:83
3030
|
3131
LL | println!("first positional arg {}, second positional arg {}, _x is {}", 1, 2, y = _x);
32-
| - ^ this named argument is only referred to by position in formatting string
33-
| |
34-
| this formatting argument uses named argument `y` by position
32+
| -- ^ this named argument is referred to by position in formatting string
33+
| |
34+
| this formatting argument uses named argument `y` by position
3535
|
3636
help: use the named argument by name to avoid ambiguity
3737
|
@@ -42,9 +42,9 @@ warning: named argument `_x` is not used by name
4242
--> $DIR/issue-98466.rs:19:34
4343
|
4444
LL | let _f = format!("_x is {}", _x = 5);
45-
| - ^^ this named argument is only referred to by position in formatting string
46-
| |
47-
| this formatting argument uses named argument `_x` by position
45+
| -- ^^ this named argument is referred to by position in formatting string
46+
| |
47+
| this formatting argument uses named argument `_x` by position
4848
|
4949
help: use the named argument by name to avoid ambiguity
5050
|
@@ -55,9 +55,9 @@ warning: named argument `y` is not used by name
5555
--> $DIR/issue-98466.rs:22:34
5656
|
5757
LL | let _f = format!("_x is {}", y = _x);
58-
| - ^ this named argument is only referred to by position in formatting string
59-
| |
60-
| this formatting argument uses named argument `y` by position
58+
| -- ^ this named argument is referred to by position in formatting string
59+
| |
60+
| this formatting argument uses named argument `y` by position
6161
|
6262
help: use the named argument by name to avoid ambiguity
6363
|
@@ -68,9 +68,9 @@ warning: named argument `y` is not used by name
6868
--> $DIR/issue-98466.rs:25:91
6969
|
7070
LL | let _f = format!("first positional arg {}, second positional arg {}, _x is {}", 1, 2, y = _x);
71-
| - ^ this named argument is only referred to by position in formatting string
72-
| |
73-
| this formatting argument uses named argument `y` by position
71+
| -- ^ this named argument is referred to by position in formatting string
72+
| |
73+
| this formatting argument uses named argument `y` by position
7474
|
7575
help: use the named argument by name to avoid ambiguity
7676
|

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