Fix incorrect span when using byte-escaped rbrace

Fix #103826.

compiler/rustc_parse_format/src/lib.rs

@@ -38,6 +38,24 @@ impl InnerSpan {
     }
 }
 
+/// The location and before/after width of a character whose width has changed from its source code
+/// representation
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub struct InnerWidthMapping {
+    /// Index of the character in the source
+    pub position: usize,
+    /// The inner width in characters
+    pub before: usize,
+    /// The transformed width in characters
+    pub after: usize,
+}
+
+impl InnerWidthMapping {
+    pub fn new(position: usize, before: usize, after: usize) -> InnerWidthMapping {
+        InnerWidthMapping { position, before, after }
+    }
+}
+
 /// The type of format string that we are parsing.
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub enum ParseMode {
@@ -200,8 +218,8 @@ pub struct Parser<'a> {
     style: Option<usize>,
     /// Start and end byte offset of every successfully parsed argument
     pub arg_places: Vec<InnerSpan>,
-    /// Characters that need to be shifted
-    skips: Vec<usize>,
+    /// Characters whose length has been changed from their in-code representation
+    width_map: Vec<InnerWidthMapping>,
     /// Span of the last opening brace seen, used for error reporting
     last_opening_brace: Option<InnerSpan>,
     /// Whether the source string is comes from `println!` as opposed to `format!` or `print!`
@@ -224,7 +242,7 @@ impl<'a> Iterator for Parser<'a> {
                 '{' => {
                     let curr_last_brace = self.last_opening_brace;
                     let byte_pos = self.to_span_index(pos);
-                    let lbrace_end = self.to_span_index(pos + 1);
+                    let lbrace_end = InnerOffset(byte_pos.0 + self.to_span_width(pos));
                     self.last_opening_brace = Some(byte_pos.to(lbrace_end));
                     self.cur.next();
                     if self.consume('{') {
@@ -233,12 +251,15 @@ impl<'a> Iterator for Parser<'a> {
                         Some(String(self.string(pos + 1)))
                     } else {
                         let arg = self.argument(lbrace_end);
-                        if let Some(rbrace_byte_idx) = self.must_consume('}') {
-                            let lbrace_inner_offset = self.to_span_index(pos);
-                            let rbrace_inner_offset = self.to_span_index(rbrace_byte_idx);
+                        if let Some(rbrace_pos) = self.must_consume('}') {
                             if self.is_literal {
+                                let lbrace_byte_pos = self.to_span_index(pos);
+                                let rbrace_byte_pos = self.to_span_index(rbrace_pos);
+
+                                let width = self.to_span_width(rbrace_pos);
+
                                 self.arg_places.push(
-                                    lbrace_inner_offset.to(InnerOffset(rbrace_inner_offset.0 + 1)),
+                                    lbrace_byte_pos.to(InnerOffset(rbrace_byte_pos.0 + width)),
                                 );
                             }
                         } else {
@@ -285,7 +306,7 @@ impl<'a> Parser<'a> {
         append_newline: bool,
         mode: ParseMode,
     ) -> Parser<'a> {
-        let (skips, is_literal) = find_skips_from_snippet(snippet, style);
+        let (width_map, is_literal) = find_width_map_from_snippet(snippet, style);
         Parser {
             mode,
             input: s,
@@ -294,7 +315,7 @@ impl<'a> Parser<'a> {
             curarg: 0,
             style,
             arg_places: vec![],
-            skips,
+            width_map,
             last_opening_brace: None,
             append_newline,
             is_literal,
@@ -367,21 +388,34 @@ impl<'a> Parser<'a> {
         None
     }
 
+    fn remap_pos(&self, mut pos: usize) -> InnerOffset {
+        for width in &self.width_map {
+            if pos > width.position {
+                pos += width.before - width.after;
+            } else if pos == width.position && width.after == 0 {
+                pos += width.before;
+            } else {
+                break;
+            }
+        }
+
+        InnerOffset(pos)
+    }
+
     fn to_span_index(&self, pos: usize) -> InnerOffset {
-        let mut pos = pos;
         // This handles the raw string case, the raw argument is the number of #
         // in r###"..."### (we need to add one because of the `r`).
         let raw = self.style.map_or(0, |raw| raw + 1);
-        for skip in &self.skips {
-            if pos > *skip {
-                pos += 1;
-            } else if pos == *skip && raw == 0 {
-                pos += 1;
-            } else {
-                break;
-            }
+        let pos = self.remap_pos(pos);
+        InnerOffset(raw + pos.0 + 1)
+    }
+
+    fn to_span_width(&self, pos: usize) -> usize {
+        let pos = self.remap_pos(pos);
+        match self.width_map.iter().find(|w| w.position == pos.0) {
+            Some(w) => w.before,
+            None => 1,
         }
-        InnerOffset(raw + pos + 1)
     }
 
     fn span(&self, start_pos: usize, end_pos: usize) -> InnerSpan {
@@ -809,10 +843,10 @@ impl<'a> Parser<'a> {
 /// Finds the indices of all characters that have been processed and differ between the actual
 /// written code (code snippet) and the `InternedString` that gets processed in the `Parser`
 /// in order to properly synthesise the intra-string `Span`s for error diagnostics.
-fn find_skips_from_snippet(
+fn find_width_map_from_snippet(
     snippet: Option<string::String>,
     str_style: Option<usize>,
-) -> (Vec<usize>, bool) {
+) -> (Vec<InnerWidthMapping>, bool) {
     let snippet = match snippet {
         Some(ref s) if s.starts_with('"') || s.starts_with("r\"") || s.starts_with("r#") => s,
         _ => return (vec![], false),
@@ -825,43 +859,39 @@ fn find_skips_from_snippet(
     let snippet = &snippet[1..snippet.len() - 1];
 
     let mut s = snippet.char_indices();
-    let mut skips = vec![];
+    let mut width_mappings = vec![];
     while let Some((pos, c)) = s.next() {
         match (c, s.clone().next()) {
             // skip whitespace and empty lines ending in '\\'
-            ('\\', Some((next_pos, '\n'))) => {
-                skips.push(pos);
-                skips.push(next_pos);
+            ('\\', Some((_, '\n'))) => {
                 let _ = s.next();
+                let mut width = 2;
 
-                while let Some((pos, c)) = s.clone().next() {
+                while let Some((_, c)) = s.clone().next() {
                     if matches!(c, ' ' | '\n' | '\t') {
-                        skips.push(pos);
+                        width += 1;
                         let _ = s.next();
                     } else {
                         break;
                     }
                 }
+
+                width_mappings.push(InnerWidthMapping::new(pos, width, 0));
             }
-            ('\\', Some((next_pos, 'n' | 't' | 'r' | '0' | '\\' | '\'' | '\"'))) => {
-                skips.push(next_pos);
+            ('\\', Some((_, 'n' | 't' | 'r' | '0' | '\\' | '\'' | '\"'))) => {
+                width_mappings.push(InnerWidthMapping::new(pos, 2, 1));
                 let _ = s.next();
             }
             ('\\', Some((_, 'x'))) => {
-                for _ in 0..3 {
-                    // consume `\xAB` literal
-                    if let Some((pos, _)) = s.next() {
-                        skips.push(pos);
-                    } else {
-                        break;
-                    }
-                }
+                // consume `\xAB` literal
+                s.nth(2);
+                width_mappings.push(InnerWidthMapping::new(pos, 4, 1));
             }
             ('\\', Some((_, 'u'))) => {
-                if let Some((pos, _)) = s.next() {
-                    skips.push(pos);
-                }
-                if let Some((next_pos, next_c)) = s.next() {
+                let mut width = 2;
+                let _ = s.next();
+
+                if let Some((_, next_c)) = s.next() {
                     if next_c == '{' {
                         // consume up to 6 hexanumeric chars
                         let digits_len =
@@ -881,31 +911,32 @@ fn find_skips_from_snippet(
                         let required_skips = digits_len.saturating_sub(len_utf8.saturating_sub(1));
 
                         // skip '{' and '}' also
-                        for pos in (next_pos..).take(required_skips + 2) {
-                            skips.push(pos)
-                        }
+                        width += required_skips + 2;
 
                         s.nth(digits_len);
                     } else if next_c.is_digit(16) {
-                        skips.push(next_pos);
+                        width += 1;
+
                         // We suggest adding `{` and `}` when appropriate, accept it here as if
                         // it were correct
                         let mut i = 0; // consume up to 6 hexanumeric chars
-                        while let (Some((next_pos, c)), _) = (s.next(), i < 6) {
+                        while let (Some((_, c)), _) = (s.next(), i < 6) {
                             if c.is_digit(16) {
-                                skips.push(next_pos);
+                                width += 1;
                             } else {
                                 break;
                             }
                             i += 1;
                         }
                     }
                 }
+
+                width_mappings.push(InnerWidthMapping::new(pos, width, 1));
             }
             _ => {}
         }
     }
-    (skips, true)
+    (width_mappings, true)
 }
 
 #[cfg(test)]

src/test/ui/fmt/issue-103826.rs

@@ -0,0 +1,8 @@
+fn main() {
+    format!("{\x7D");
+    //~^ ERROR 1 positional argument in format string, but no arguments were given
+    format!("\x7B\x7D");
+    //~^ ERROR 1 positional argument in format string, but no arguments were given
+    format!("{\x7D {\x7D");
+    //~^ ERROR 2 positional arguments in format string, but no arguments were given
+}

src/test/ui/fmt/issue-103826.stderr

@@ -0,0 +1,20 @@
+error: 1 positional argument in format string, but no arguments were given
+  --> $DIR/issue-103826.rs:2:14
+   |
+LL |     format!("{\x7D");
+   |              ^^^^^
+
+error: 1 positional argument in format string, but no arguments were given
+  --> $DIR/issue-103826.rs:4:14
+   |
+LL |     format!("\x7B\x7D");
+   |              ^^^^^^^^
+
+error: 2 positional arguments in format string, but no arguments were given
+  --> $DIR/issue-103826.rs:6:14
+   |
+LL |     format!("{\x7D {\x7D");
+   |              ^^^^^ ^^^^^
+
+error: aborting due to 3 previous errors
+