compiler/rustc_parse/src/lexer/unescape_error_reporting.rs

   1 //! Utilities for rendering escape sequence errors as diagnostics.
   2
   3 use std::iter::once;
   4 use std::ops::Range;
   5
   6 use rustc_errors::{pluralize, Applicability, Handler};
   7 use rustc_lexer::unescape::{EscapeError, Mode};
   8 use rustc_span::{BytePos, Span};
   9
  10 pub(crate) fn emit_unescape_error(
  11     handler: &Handler,
  12     // interior part of the literal, without quotes
  13     lit: &str,
  14     // full span of the literal, including quotes
  15     span_with_quotes: Span,
  16     // interior span of the literal, without quotes
  17     span: Span,
  18     mode: Mode,
  19     // range of the error inside `lit`
  20     range: Range<usize>,
  21     error: EscapeError,
  22 ) {
  23     tracing::debug!(
  24         "emit_unescape_error: {:?}, {:?}, {:?}, {:?}, {:?}",
  25         lit,
  26         span_with_quotes,
  27         mode,
  28         range,
  29         error
  30     );
  31     let last_char = || {
  32         let c = lit[range.clone()].chars().rev().next().unwrap();
  33         let span = span.with_lo(span.hi() - BytePos(c.len_utf8() as u32));
  34         (c, span)
  35     };
  36     match error {
  37         EscapeError::LoneSurrogateUnicodeEscape => {
  38             handler
  39                 .struct_span_err(span, "invalid unicode character escape")
  40                 .span_label(span, "invalid escape")
  41                 .help("unicode escape must not be a surrogate")
  42                 .emit();
  43         }
  44         EscapeError::OutOfRangeUnicodeEscape => {
  45             handler
  46                 .struct_span_err(span, "invalid unicode character escape")
  47                 .span_label(span, "invalid escape")
  48                 .help("unicode escape must be at most 10FFFF")
  49                 .emit();
  50         }
  51         EscapeError::MoreThanOneChar => {
  52             use unicode_normalization::{char::is_combining_mark, UnicodeNormalization};
  53
  54             let mut has_help = false;
  55             let mut handler = handler.struct_span_err(
  56                 span_with_quotes,
  57                 "character literal may only contain one codepoint",
  58             );
  59
  60             if lit.chars().skip(1).all(|c| is_combining_mark(c)) {
  61                 let escaped_marks =
  62                     lit.chars().skip(1).map(|c| c.escape_default().to_string()).collect::<Vec<_>>();
  63                 handler.span_note(
  64                     span,
  65                     &format!(
  66                         "this `{}` is followed by the combining mark{} `{}`",
  67                         lit.chars().next().unwrap(),
  68                         pluralize!(escaped_marks.len()),
  69                         escaped_marks.join(""),
  70                     ),
  71                 );
  72                 let normalized = lit.nfc().to_string();
  73                 if normalized.chars().count() == 1 {
  74                     has_help = true;
  75                     handler.span_suggestion(
  76                         span,
  77                         &format!(
  78                             "consider using the normalized form `{}` of this character",
  79                             normalized.chars().next().unwrap().escape_default()
  80                         ),
  81                         normalized,
  82                         Applicability::MachineApplicable,
  83                     );
  84                 }
  85             } else {
  86                 let printable: Vec<char> = lit
  87                     .chars()
  88                     .filter(|&x| {
  89                         unicode_width::UnicodeWidthChar::width(x).unwrap_or(0) != 0
  90                             && !x.is_whitespace()
  91                     })
  92                     .collect();
  93
  94                 if let [ch] = printable.as_slice() {
  95                     has_help = true;
  96
  97                     handler.span_note(
  98                         span,
  99                         &format!(
 100                             "there are non-printing characters, the full sequence is `{}`",
 101                             lit.escape_default(),
 102                         ),
 103                     );
 104
 105                     handler.span_suggestion(
 106                         span,
 107                         "consider removing the non-printing characters",
 108                         ch.to_string(),
 109                         Applicability::MaybeIncorrect,
 110                     );
 111                 }
 112             }
 113
 114             if !has_help {
 115                 let (prefix, msg) = if mode.is_bytes() {
 116                     ("b", "if you meant to write a byte string literal, use double quotes")
 117                 } else {
 118                     ("", "if you meant to write a `str` literal, use double quotes")
 119                 };
 120
 121                 handler.span_suggestion(
 122                     span_with_quotes,
 123                     msg,
 124                     format!("{}\"{}\"", prefix, lit),
 125                     Applicability::MachineApplicable,
 126                 );
 127             }
 128
 129             handler.emit();
 130         }
 131         EscapeError::EscapeOnlyChar => {
 132             let (c, char_span) = last_char();
 133
 134             let msg = if mode.is_bytes() {
 135                 "byte constant must be escaped"
 136             } else {
 137                 "character constant must be escaped"
 138             };
 139             handler
 140                 .struct_span_err(span, &format!("{}: `{}`", msg, escaped_char(c)))
 141                 .span_suggestion(
 142                     char_span,
 143                     "escape the character",
 144                     c.escape_default().to_string(),
 145                     Applicability::MachineApplicable,
 146                 )
 147                 .emit()
 148         }
 149         EscapeError::BareCarriageReturn => {
 150             let msg = if mode.in_double_quotes() {
 151                 "bare CR not allowed in string, use `\\r` instead"
 152             } else {
 153                 "character constant must be escaped: `\\r`"
 154             };
 155             handler
 156                 .struct_span_err(span, msg)
 157                 .span_suggestion(
 158                     span,
 159                     "escape the character",
 160                     "\\r".to_string(),
 161                     Applicability::MachineApplicable,
 162                 )
 163                 .emit();
 164         }
 165         EscapeError::BareCarriageReturnInRawString => {
 166             assert!(mode.in_double_quotes());
 167             let msg = "bare CR not allowed in raw string";
 168             handler.span_err(span, msg);
 169         }
 170         EscapeError::InvalidEscape => {
 171             let (c, span) = last_char();
 172
 173             let label =
 174                 if mode.is_bytes() { "unknown byte escape" } else { "unknown character escape" };
 175             let ec = escaped_char(c);
 176             let mut diag = handler.struct_span_err(span, &format!("{}: `{}`", label, ec));
 177             diag.span_label(span, label);
 178             if c == '{' || c == '}' && !mode.is_bytes() {
 179                 diag.help(
 180                     "if used in a formatting string, curly braces are escaped with `{{` and `}}`",
 181                 );
 182             } else if c == '\r' {
 183                 diag.help(
 184                     "this is an isolated carriage return; consider checking your editor and \
 185                      version control settings",
 186                 );
 187             } else {
 188                 diag.help(
 189                     "for more information, visit \
 190                      <https://static.rust-lang.org/doc/master/reference.html#literals>",
 191                 );
 192             }
 193             diag.emit();
 194         }
 195         EscapeError::TooShortHexEscape => {
 196             handler.span_err(span, "numeric character escape is too short")
 197         }
 198         EscapeError::InvalidCharInHexEscape | EscapeError::InvalidCharInUnicodeEscape => {
 199             let (c, span) = last_char();
 200
 201             let msg = if error == EscapeError::InvalidCharInHexEscape {
 202                 "invalid character in numeric character escape"
 203             } else {
 204                 "invalid character in unicode escape"
 205             };
 206             let c = escaped_char(c);
 207
 208             handler
 209                 .struct_span_err(span, &format!("{}: `{}`", msg, c))
 210                 .span_label(span, msg)
 211                 .emit();
 212         }
 213         EscapeError::NonAsciiCharInByte => {
 214             assert!(mode.is_bytes());
 215             let (c, span) = last_char();
 216             let mut err = handler.struct_span_err(span, "non-ASCII character in byte constant");
 217             let postfix = if unicode_width::UnicodeWidthChar::width(c).unwrap_or(1) == 0 {
 218                 format!(" but is {:?}", c)
 219             } else {
 220                 String::new()
 221             };
 222             err.span_label(span, &format!("byte constant must be ASCII{}", postfix));
 223             if (c as u32) <= 0xFF {
 224                 err.span_suggestion(
 225                     span,
 226                     &format!(
 227                         "if you meant to use the unicode code point for {:?}, use a \\xHH escape",
 228                         c
 229                     ),
 230                     format!("\\x{:X}", c as u32),
 231                     Applicability::MaybeIncorrect,
 232                 );
 233             } else if matches!(mode, Mode::Byte) {
 234                 err.span_label(span, "this multibyte character does not fit into a single byte");
 235             } else if matches!(mode, Mode::ByteStr) {
 236                 let mut utf8 = String::new();
 237                 utf8.push(c);
 238                 err.span_suggestion(
 239                     span,
 240                     &format!(
 241                         "if you meant to use the UTF-8 encoding of {:?}, use \\xHH escapes",
 242                         c
 243                     ),
 244                     utf8.as_bytes()
 245                         .iter()
 246                         .map(|b: &u8| format!("\\x{:X}", *b))
 247                         .fold("".to_string(), |a, c| a + &c),
 248                     Applicability::MaybeIncorrect,
 249                 );
 250             }
 251             err.emit();
 252         }
 253         EscapeError::NonAsciiCharInByteString => {
 254             assert!(mode.is_bytes());
 255             let (c, span) = last_char();
 256             let postfix = if unicode_width::UnicodeWidthChar::width(c).unwrap_or(1) == 0 {
 257                 format!(" but is {:?}", c)
 258             } else {
 259                 String::new()
 260             };
 261             handler
 262                 .struct_span_err(span, "raw byte string must be ASCII")
 263                 .span_label(span, &format!("must be ASCII{}", postfix))
 264                 .emit();
 265         }
 266         EscapeError::OutOfRangeHexEscape => {
 267             handler
 268                 .struct_span_err(span, "out of range hex escape")
 269                 .span_label(span, "must be a character in the range [\\x00-\\x7f]")
 270                 .emit();
 271         }
 272         EscapeError::LeadingUnderscoreUnicodeEscape => {
 273             let (c, span) = last_char();
 274             let msg = "invalid start of unicode escape";
 275             handler
 276                 .struct_span_err(span, &format!("{}: `{}`", msg, c))
 277                 .span_label(span, msg)
 278                 .emit();
 279         }
 280         EscapeError::OverlongUnicodeEscape => {
 281             handler
 282                 .struct_span_err(span, "overlong unicode escape")
 283                 .span_label(span, "must have at most 6 hex digits")
 284                 .emit();
 285         }
 286         EscapeError::UnclosedUnicodeEscape => handler
 287             .struct_span_err(span, "unterminated unicode escape")
 288             .span_label(span, "missing a closing `}`")
 289             .span_suggestion_verbose(
 290                 span.shrink_to_hi(),
 291                 "terminate the unicode escape",
 292                 "}".to_string(),
 293                 Applicability::MaybeIncorrect,
 294             )
 295             .emit(),
 296         EscapeError::NoBraceInUnicodeEscape => {
 297             let msg = "incorrect unicode escape sequence";
 298             let mut diag = handler.struct_span_err(span, msg);
 299
 300             let mut suggestion = "\\u{".to_owned();
 301             let mut suggestion_len = 0;
 302             let (c, char_span) = last_char();
 303             let chars = once(c).chain(lit[range.end..].chars());
 304             for c in chars.take(6).take_while(|c| c.is_digit(16)) {
 305                 suggestion.push(c);
 306                 suggestion_len += c.len_utf8();
 307             }
 308
 309             if suggestion_len > 0 {
 310                 suggestion.push('}');
 311                 let hi = char_span.lo() + BytePos(suggestion_len as u32);
 312                 diag.span_suggestion(
 313                     span.with_hi(hi),
 314                     "format of unicode escape sequences uses braces",
 315                     suggestion,
 316                     Applicability::MaybeIncorrect,
 317                 );
 318             } else {
 319                 diag.span_label(span, msg);
 320                 diag.help("format of unicode escape sequences is `\\u{...}`");
 321             }
 322
 323             diag.emit();
 324         }
 325         EscapeError::UnicodeEscapeInByte => {
 326             let msg = "unicode escape in byte string";
 327             handler
 328                 .struct_span_err(span, msg)
 329                 .span_label(span, msg)
 330                 .help("unicode escape sequences cannot be used as a byte or in a byte string")
 331                 .emit();
 332         }
 333         EscapeError::EmptyUnicodeEscape => {
 334             handler
 335                 .struct_span_err(span, "empty unicode escape")
 336                 .span_label(span, "this escape must have at least 1 hex digit")
 337                 .emit();
 338         }
 339         EscapeError::ZeroChars => {
 340             let msg = "empty character literal";
 341             handler.struct_span_err(span, msg).span_label(span, msg).emit()
 342         }
 343         EscapeError::LoneSlash => {
 344             let msg = "invalid trailing slash in literal";
 345             handler.struct_span_err(span, msg).span_label(span, msg).emit();
 346         }
 347         EscapeError::UnskippedWhitespaceWarning => {
 348             let (c, char_span) = last_char();
 349             let msg =
 350                 format!("non-ASCII whitespace symbol '{}' is not skipped", c.escape_unicode());
 351             handler.struct_span_warn(span, &msg).span_label(char_span, &msg).emit();
 352         }
 353         EscapeError::MultipleSkippedLinesWarning => {
 354             let msg = "multiple lines skipped by escaped newline";
 355             let bottom_msg = "skipping everything up to and including this point";
 356             handler.struct_span_warn(span, msg).span_label(span, bottom_msg).emit();
 357         }
 358     }
 359 }
 360
 361 /// Pushes a character to a message string for error reporting
 362 pub(crate) fn escaped_char(c: char) -> String {
 363     match c {
 364         '\u{20}'..='\u{7e}' => {
 365             // Don't escape \, ' or " for user-facing messages
 366             c.to_string()
 367         }
 368         _ => c.escape_default().to_string(),
 369     }
 370 }