diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 1c9c6834c100c..f0056cb79766a 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -1154,11 +1154,12 @@ pub fn expand_preparsed_format_args(
// account for `"` and account for raw strings `r#`
let padding = str_style.map(|i| i + 2).unwrap_or(1);
for sub in foreign::$kind::iter_subs(fmt_str, padding) {
- let trn = match sub.translate() {
- Some(trn) => trn,
+ let (trn, success) = match sub.translate() {
+ Ok(trn) => (trn, true),
+ Err(Some(msg)) => (msg, false),
// If it has no translation, don't call it out specifically.
- None => continue,
+ _ => continue,
};
let pos = sub.position();
@@ -1175,9 +1176,24 @@ pub fn expand_preparsed_format_args(
if let Some(inner_sp) = pos {
let sp = fmt_sp.from_inner(inner_sp);
- suggestions.push((sp, trn));
+
+ if success {
+ suggestions.push((sp, trn));
+ } else {
+ diag.span_note(
+ sp,
+ &format!("format specifiers use curly braces, and {}", trn),
+ );
+ }
} else {
- diag.help(&format!("`{}` should be written as `{}`", sub, trn));
+ if success {
+ diag.help(&format!("`{}` should be written as `{}`", sub, trn));
+ } else {
+ diag.note(&format!(
+ "`{}` should use curly braces, and {}",
+ sub, trn
+ ));
+ }
}
}
diff --git a/compiler/rustc_builtin_macros/src/format_foreign.rs b/compiler/rustc_builtin_macros/src/format_foreign.rs
index 0cc520e5bd1f0..bfddd7073ff2c 100644
--- a/compiler/rustc_builtin_macros/src/format_foreign.rs
+++ b/compiler/rustc_builtin_macros/src/format_foreign.rs
@@ -1,4 +1,4 @@
-pub mod printf {
+pub(crate) mod printf {
use super::strcursor::StrCursor as Cur;
use rustc_span::InnerSpan;
@@ -36,10 +36,10 @@ pub mod printf {
///
/// This ignores cases where the substitution does not have an exact equivalent, or where
/// the substitution would be unnecessary.
- pub fn translate(&self) -> Option<String> {
+ pub fn translate(&self) -> Result<String, Option<String>> {
match *self {
Substitution::Format(ref fmt) => fmt.translate(),
- Substitution::Escape => None,
+ Substitution::Escape => Err(None),
}
}
}
@@ -68,9 +68,9 @@ pub mod printf {
impl Format<'_> {
/// Translate this directive into an equivalent Rust formatting directive.
///
- /// Returns `None` in cases where the `printf` directive does not have an exact Rust
+ /// Returns `Err` in cases where the `printf` directive does not have an exact Rust
/// equivalent, rather than guessing.
- pub fn translate(&self) -> Option<String> {
+ pub fn translate(&self) -> Result<String, Option<String>> {
use std::fmt::Write;
let (c_alt, c_zero, c_left, c_plus) = {
@@ -84,7 +84,12 @@ pub mod printf {
'0' => c_zero = true,
'-' => c_left = true,
'+' => c_plus = true,
- _ => return None,
+ _ => {
+ return Err(Some(format!(
+ "the flag `{}` is unknown or unsupported",
+ c
+ )));
+ }
}
}
(c_alt, c_zero, c_left, c_plus)
@@ -104,7 +109,9 @@ pub mod printf {
let width = match self.width {
Some(Num::Next) => {
// NOTE: Rust doesn't support this.
- return None;
+ return Err(Some(
+ "you have to use a positional or named parameter for the width".to_string(),
+ ));
}
w @ Some(Num::Arg(_)) => w,
w @ Some(Num::Num(_)) => w,
@@ -125,13 +132,21 @@ pub mod printf {
"p" => (Some(self.type_), false, true),
"g" => (Some("e"), true, false),
"G" => (Some("E"), true, false),
- _ => return None,
+ _ => {
+ return Err(Some(format!(
+ "the conversion specifier `{}` is unknown or unsupported",
+ self.type_
+ )));
+ }
};
let (fill, width, precision) = match (is_int, width, precision) {
(true, Some(_), Some(_)) => {
// Rust can't duplicate this insanity.
- return None;
+ return Err(Some(
+ "width and precision cannot both be specified for integer conversions"
+ .to_string(),
+ ));
}
(true, None, Some(p)) => (Some("0"), Some(p), None),
(true, w, None) => (fill, w, None),
@@ -169,7 +184,17 @@ pub mod printf {
s.push('{');
if let Some(arg) = self.parameter {
- write!(s, "{}", arg.checked_sub(1)?).ok()?;
+ match write!(
+ s,
+ "{}",
+ match arg.checked_sub(1) {
+ Some(a) => a,
+ None => return Err(None),
+ }
+ ) {
+ Err(_) => return Err(None),
+ _ => {}
+ }
}
if has_options {
@@ -199,12 +224,18 @@ pub mod printf {
}
if let Some(width) = width {
- width.translate(&mut s).ok()?;
+ match width.translate(&mut s) {
+ Err(_) => return Err(None),
+ _ => {}
+ }
}
if let Some(precision) = precision {
s.push('.');
- precision.translate(&mut s).ok()?;
+ match precision.translate(&mut s) {
+ Err(_) => return Err(None),
+ _ => {}
+ }
}
if let Some(type_) = type_ {
@@ -213,7 +244,7 @@ pub mod printf {
}
s.push('}');
- Some(s)
+ Ok(s)
}
}
@@ -623,11 +654,11 @@ pub mod shell {
}
}
- pub fn translate(&self) -> Option<String> {
+ pub fn translate(&self) -> Result<String, Option<String>> {
match *self {
- Substitution::Ordinal(n, _) => Some(format!("{{{}}}", n)),
- Substitution::Name(n, _) => Some(format!("{{{}}}", n)),
- Substitution::Escape(_) => None,
+ Substitution::Ordinal(n, _) => Ok(format!("{{{}}}", n)),
+ Substitution::Name(n, _) => Ok(format!("{{{}}}", n)),
+ Substitution::Escape(_) => Err(None),
}
}
}
diff --git a/compiler/rustc_builtin_macros/src/format_foreign/printf/tests.rs b/compiler/rustc_builtin_macros/src/format_foreign/printf/tests.rs
index 33c54c9cee001..1336aab731674 100644
--- a/compiler/rustc_builtin_macros/src/format_foreign/printf/tests.rs
+++ b/compiler/rustc_builtin_macros/src/format_foreign/printf/tests.rs
@@ -3,7 +3,7 @@ use super::{iter_subs, parse_next_substitution as pns, Format as F, Num as N, Su
macro_rules! assert_eq_pnsat {
($lhs:expr, $rhs:expr) => {
assert_eq!(
- pns($lhs).and_then(|(s, _)| s.translate()),
+ pns($lhs).and_then(|(s, _)| s.translate().ok()),
$rhs.map(<String as From<&str>>::from)
)
};
@@ -98,7 +98,7 @@ fn test_parse() {
#[test]
fn test_iter() {
let s = "The %d'th word %% is: `%.*s` %!\n";
- let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate()).collect();
+ let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate().ok()).collect();
assert_eq!(
subs.iter().map(|ms| ms.as_ref().map(|s| &s[..])).collect::<Vec<_>>(),
vec![Some("{}"), None, Some("{:.*}"), None]
diff --git a/compiler/rustc_builtin_macros/src/format_foreign/shell/tests.rs b/compiler/rustc_builtin_macros/src/format_foreign/shell/tests.rs
index ed8fe81dfcdd8..f5f82732f2034 100644
--- a/compiler/rustc_builtin_macros/src/format_foreign/shell/tests.rs
+++ b/compiler/rustc_builtin_macros/src/format_foreign/shell/tests.rs
@@ -3,7 +3,7 @@ use super::{parse_next_substitution as pns, Substitution as S};
macro_rules! assert_eq_pnsat {
($lhs:expr, $rhs:expr) => {
assert_eq!(
- pns($lhs).and_then(|(f, _)| f.translate()),
+ pns($lhs).and_then(|(f, _)| f.translate().ok()),
$rhs.map(<String as From<&str>>::from)
)
};
@@ -37,7 +37,7 @@ fn test_parse() {
fn test_iter() {
use super::iter_subs;
let s = "The $0'th word $$ is: `$WORD` $!\n";
- let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate()).collect();
+ let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate().ok()).collect();
assert_eq!(
subs.iter().map(|ms| ms.as_ref().map(|s| &s[..])).collect::<Vec<_>>(),
vec![Some("{0}"), None, Some("{WORD}")]
diff --git a/src/test/ui/fmt/issue-89173.rs b/src/test/ui/fmt/issue-89173.rs
new file mode 100644
index 0000000000000..96277d4d0d9d7
--- /dev/null
+++ b/src/test/ui/fmt/issue-89173.rs
@@ -0,0 +1,14 @@
+// Regression test for #89173: Make sure a helpful note is issued for
+// printf-style format strings using `*` to specify the width.
+
+fn main() {
+ let num = 0x0abcde;
+ let width = 6;
+ print!("%0*x", width, num);
+ //~^ ERROR: multiple unused formatting arguments
+ //~| NOTE: multiple missing formatting specifiers
+ //~| NOTE: argument never used
+ //~| NOTE: argument never used
+ //~| NOTE: format specifiers use curly braces, and you have to use a positional or named parameter for the width
+ //~| NOTE: printf formatting not supported
+}
diff --git a/src/test/ui/fmt/issue-89173.stderr b/src/test/ui/fmt/issue-89173.stderr
new file mode 100644
index 0000000000000..7b21e0a4fc896
--- /dev/null
+++ b/src/test/ui/fmt/issue-89173.stderr
@@ -0,0 +1,18 @@
+error: multiple unused formatting arguments
+ --> $DIR/issue-89173.rs:7:20
+ |
+LL | print!("%0*x", width, num);
+ | ------ ^^^^^ ^^^ argument never used
+ | | |
+ | | argument never used
+ | multiple missing formatting specifiers
+ |
+note: format specifiers use curly braces, and you have to use a positional or named parameter for the width
+ --> $DIR/issue-89173.rs:7:13
+ |
+LL | print!("%0*x", width, num);
+ | ^^^^
+ = note: printf formatting not supported; see the documentation for `std::fmt`
+
+error: aborting due to previous error
+