Rollup merge of #92460 - dwrensha:fix-92267, r=petrochenkov

[rustc_builtin_macros] add indices to format_foreign::printf::Substitution::Escape

Fixes #92267.

The problem was that the escape string "%%" does not need to appear at the very beginning of the format string, but
the iterator implementation assumed that it did.

The solution follows the pattern used by `format_foregin::shell::Subtitution::Escape`: https://github.com/rust-lang/rust/blob/8ed935e92dfb09ae388344b12284bf5110cf9265/compiler/rustc_builtin_macros/src/format_foreign.rs#L629

compiler/rustc_builtin_macros/src/format_foreign.rs

@@ -7,28 +7,29 @@ pub(crate) mod printf {
  pub enum Substitution<'a> {
  /// A formatted output substitution with its internal byte offset.
  Format(Format<'a>),
- /// A literal `%%` escape.
- Escape,
+ /// A literal `%%` escape, with its start and end indices.
+ Escape((usize, usize)),
  }
 
  impl<'a> Substitution<'a> {
  pub fn as_str(&self) -> &str {
  match *self {
  Substitution::Format(ref fmt) => fmt.span,
- Substitution::Escape => "%%",
+ Substitution::Escape(_) => "%%",
  }
  }
 
  pub fn position(&self) -> Option<InnerSpan> {
  match *self {
  Substitution::Format(ref fmt) => Some(fmt.position),
- _ => None,
+ Substitution::Escape((start, end)) => Some(InnerSpan::new(start, end)),
  }
  }
 
  pub fn set_position(&mut self, start: usize, end: usize) {
- if let Substitution::Format(ref mut fmt) = self {
- fmt.position = InnerSpan::new(start, end);
+ match self {
+ Substitution::Format(ref mut fmt) => fmt.position = InnerSpan::new(start, end),
+ Substitution::Escape(ref mut pos) => *pos = (start, end),
  }
  }
 
@@ -39,7 +40,7 @@ pub(crate) mod printf {
  pub fn translate(&self) -> Result<String, Option<String>> {
  match *self {
  Substitution::Format(ref fmt) => fmt.translate(),
- Substitution::Escape => Err(None),
+ Substitution::Escape(_) => Err(None),
  }
  }
  }
@@ -304,14 +305,9 @@ pub(crate) mod printf {
  fn next(&mut self) -> Option<Self::Item> {
  let (mut sub, tail) = parse_next_substitution(self.s)?;
  self.s = tail;
- match sub {
- Substitution::Format(_) => {
- if let Some(inner_span) = sub.position() {
- sub.set_position(inner_span.start + self.pos, inner_span.end + self.pos);
- self.pos += inner_span.end;
- }
- }
- Substitution::Escape => self.pos += 2,
+ if let Some(InnerSpan { start, end }) = sub.position() {
+ sub.set_position(start + self.pos, end + self.pos);
+ self.pos += end;
  }
  Some(sub)
  }
@@ -340,7 +336,7 @@ pub(crate) mod printf {
  let at = {
  let start = s.find('%')?;
  if let '%' = s[start + 1..].chars().next()? {
- return Some((Substitution::Escape, &s[start + 2..]));
+ return Some((Substitution::Escape((start, start + 2)), &s[start + 2..]));
  }
 
  Cur::new_at(s, start)

compiler/rustc_builtin_macros/src/format_foreign/printf/tests.rs

@@ -13,9 +13,9 @@ macro_rules! assert_eq_pnsat {
 fn test_escape() {
  assert_eq!(pns("has no escapes"), None);
  assert_eq!(pns("has no escapes, either %"), None);
- assert_eq!(pns("*so* has a %% escape"), Some((S::Escape, " escape")));
- assert_eq!(pns("%% leading escape"), Some((S::Escape, " leading escape")));
- assert_eq!(pns("trailing escape %%"), Some((S::Escape, "")));
+ assert_eq!(pns("*so* has a %% escape"), Some((S::Escape((11, 13)), " escape")));
+ assert_eq!(pns("%% leading escape"), Some((S::Escape((0, 2)), " leading escape")));
+ assert_eq!(pns("trailing escape %%"), Some((S::Escape((16, 18)), "")));
 }
 
 #[test]

src/test/ui/macros/issue-92267.rs

@@ -0,0 +1,3 @@
+// check-fail
+
+pub fn main() { println!("🦀%%%", 0) } //~ ERROR argument never used

src/test/ui/macros/issue-92267.stderr

@@ -0,0 +1,16 @@
+error: argument never used
+ --> $DIR/issue-92267.rs:3:34
+ |
+LL | pub fn main() { println!("🦀%%%", 0) }
+ | ^ argument never used
+ |
+note: format specifiers use curly braces, and the conversion specifier `
+ ` is unknown or unsupported
+ --> $DIR/issue-92267.rs:3:30
+ |
+LL | pub fn main() { println!("🦀%%%", 0) }
+ | ^^
+ = note: printf formatting not supported; see the documentation for `std::fmt`
+
+error: aborting due to previous error
+