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Diffstat (limited to 'third_party/rust/regex-syntax/src/ast/mod.rs')
| -rw-r--r-- | third_party/rust/regex-syntax/src/ast/mod.rs | 1502 |
1 files changed, 1502 insertions, 0 deletions
diff --git a/third_party/rust/regex-syntax/src/ast/mod.rs b/third_party/rust/regex-syntax/src/ast/mod.rs new file mode 100644 index 0000000000..387ea3a698 --- /dev/null +++ b/third_party/rust/regex-syntax/src/ast/mod.rs @@ -0,0 +1,1502 @@ +/*! +Defines an abstract syntax for regular expressions. +*/ + +use std::cmp::Ordering; +use std::error; +use std::fmt; + +pub use crate::ast::visitor::{visit, Visitor}; + +pub mod parse; +pub mod print; +mod visitor; + +/// An error that occurred while parsing a regular expression into an abstract +/// syntax tree. +/// +/// Note that not all ASTs represents a valid regular expression. For example, +/// an AST is constructed without error for `\p{Quux}`, but `Quux` is not a +/// valid Unicode property name. That particular error is reported when +/// translating an AST to the high-level intermediate representation (`HIR`). +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Error { + /// The kind of error. + kind: ErrorKind, + /// The original pattern that the parser generated the error from. Every + /// span in an error is a valid range into this string. + pattern: String, + /// The span of this error. + span: Span, +} + +impl Error { + /// Return the type of this error. + pub fn kind(&self) -> &ErrorKind { + &self.kind + } + + /// The original pattern string in which this error occurred. + /// + /// Every span reported by this error is reported in terms of this string. + pub fn pattern(&self) -> &str { + &self.pattern + } + + /// Return the span at which this error occurred. + pub fn span(&self) -> &Span { + &self.span + } + + /// Return an auxiliary span. This span exists only for some errors that + /// benefit from being able to point to two locations in the original + /// regular expression. For example, "duplicate" errors will have the + /// main error position set to the duplicate occurrence while its + /// auxiliary span will be set to the initial occurrence. + pub fn auxiliary_span(&self) -> Option<&Span> { + use self::ErrorKind::*; + match self.kind { + FlagDuplicate { ref original } => Some(original), + FlagRepeatedNegation { ref original, .. } => Some(original), + GroupNameDuplicate { ref original, .. } => Some(original), + _ => None, + } + } +} + +/// The type of an error that occurred while building an AST. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ErrorKind { + /// The capturing group limit was exceeded. + /// + /// Note that this represents a limit on the total number of capturing + /// groups in a regex and not necessarily the number of nested capturing + /// groups. That is, the nest limit can be low and it is still possible for + /// this error to occur. + CaptureLimitExceeded, + /// An invalid escape sequence was found in a character class set. + ClassEscapeInvalid, + /// An invalid character class range was found. An invalid range is any + /// range where the start is greater than the end. + ClassRangeInvalid, + /// An invalid range boundary was found in a character class. Range + /// boundaries must be a single literal codepoint, but this error indicates + /// that something else was found, such as a nested class. + ClassRangeLiteral, + /// An opening `[` was found with no corresponding closing `]`. + ClassUnclosed, + /// Note that this error variant is no longer used. Namely, a decimal + /// number can only appear as a repetition quantifier. When the number + /// in a repetition quantifier is empty, then it gets its own specialized + /// error, `RepetitionCountDecimalEmpty`. + DecimalEmpty, + /// An invalid decimal number was given where one was expected. + DecimalInvalid, + /// A bracketed hex literal was empty. + EscapeHexEmpty, + /// A bracketed hex literal did not correspond to a Unicode scalar value. + EscapeHexInvalid, + /// An invalid hexadecimal digit was found. + EscapeHexInvalidDigit, + /// EOF was found before an escape sequence was completed. + EscapeUnexpectedEof, + /// An unrecognized escape sequence. + EscapeUnrecognized, + /// A dangling negation was used when setting flags, e.g., `i-`. + FlagDanglingNegation, + /// A flag was used twice, e.g., `i-i`. + FlagDuplicate { + /// The position of the original flag. The error position + /// points to the duplicate flag. + original: Span, + }, + /// The negation operator was used twice, e.g., `-i-s`. + FlagRepeatedNegation { + /// The position of the original negation operator. The error position + /// points to the duplicate negation operator. + original: Span, + }, + /// Expected a flag but got EOF, e.g., `(?`. + FlagUnexpectedEof, + /// Unrecognized flag, e.g., `a`. + FlagUnrecognized, + /// A duplicate capture name was found. + GroupNameDuplicate { + /// The position of the initial occurrence of the capture name. The + /// error position itself points to the duplicate occurrence. + original: Span, + }, + /// A capture group name is empty, e.g., `(?P<>abc)`. + GroupNameEmpty, + /// An invalid character was seen for a capture group name. This includes + /// errors where the first character is a digit (even though subsequent + /// characters are allowed to be digits). + GroupNameInvalid, + /// A closing `>` could not be found for a capture group name. + GroupNameUnexpectedEof, + /// An unclosed group, e.g., `(ab`. + /// + /// The span of this error corresponds to the unclosed parenthesis. + GroupUnclosed, + /// An unopened group, e.g., `ab)`. + GroupUnopened, + /// The nest limit was exceeded. The limit stored here is the limit + /// configured in the parser. + NestLimitExceeded(u32), + /// The range provided in a counted repetition operator is invalid. The + /// range is invalid if the start is greater than the end. + RepetitionCountInvalid, + /// An opening `{` was not followed by a valid decimal value. + /// For example, `x{}` or `x{]}` would fail. + RepetitionCountDecimalEmpty, + /// An opening `{` was found with no corresponding closing `}`. + RepetitionCountUnclosed, + /// A repetition operator was applied to a missing sub-expression. This + /// occurs, for example, in the regex consisting of just a `*` or even + /// `(?i)*`. It is, however, possible to create a repetition operating on + /// an empty sub-expression. For example, `()*` is still considered valid. + RepetitionMissing, + /// The Unicode class is not valid. This typically occurs when a `\p` is + /// followed by something other than a `{`. + UnicodeClassInvalid, + /// When octal support is disabled, this error is produced when an octal + /// escape is used. The octal escape is assumed to be an invocation of + /// a backreference, which is the common case. + UnsupportedBackreference, + /// When syntax similar to PCRE's look-around is used, this error is + /// returned. Some example syntaxes that are rejected include, but are + /// not necessarily limited to, `(?=re)`, `(?!re)`, `(?<=re)` and + /// `(?<!re)`. Note that all of these syntaxes are otherwise invalid; this + /// error is used to improve the user experience. + UnsupportedLookAround, + /// Hints that destructuring should not be exhaustive. + /// + /// This enum may grow additional variants, so this makes sure clients + /// don't count on exhaustive matching. (Otherwise, adding a new variant + /// could break existing code.) + #[doc(hidden)] + __Nonexhaustive, +} + +impl error::Error for Error { + // TODO: Remove this method entirely on the next breaking semver release. + #[allow(deprecated)] + fn description(&self) -> &str { + use self::ErrorKind::*; + match self.kind { + CaptureLimitExceeded => "capture group limit exceeded", + ClassEscapeInvalid => "invalid escape sequence in character class", + ClassRangeInvalid => "invalid character class range", + ClassRangeLiteral => "invalid range boundary, must be a literal", + ClassUnclosed => "unclosed character class", + DecimalEmpty => "empty decimal literal", + DecimalInvalid => "invalid decimal literal", + EscapeHexEmpty => "empty hexadecimal literal", + EscapeHexInvalid => "invalid hexadecimal literal", + EscapeHexInvalidDigit => "invalid hexadecimal digit", + EscapeUnexpectedEof => "unexpected eof (escape sequence)", + EscapeUnrecognized => "unrecognized escape sequence", + FlagDanglingNegation => "dangling flag negation operator", + FlagDuplicate { .. } => "duplicate flag", + FlagRepeatedNegation { .. } => "repeated negation", + FlagUnexpectedEof => "unexpected eof (flag)", + FlagUnrecognized => "unrecognized flag", + GroupNameDuplicate { .. } => "duplicate capture group name", + GroupNameEmpty => "empty capture group name", + GroupNameInvalid => "invalid capture group name", + GroupNameUnexpectedEof => "unclosed capture group name", + GroupUnclosed => "unclosed group", + GroupUnopened => "unopened group", + NestLimitExceeded(_) => "nest limit exceeded", + RepetitionCountInvalid => "invalid repetition count range", + RepetitionCountUnclosed => "unclosed counted repetition", + RepetitionMissing => "repetition operator missing expression", + UnicodeClassInvalid => "invalid Unicode character class", + UnsupportedBackreference => "backreferences are not supported", + UnsupportedLookAround => "look-around is not supported", + _ => unreachable!(), + } + } +} + +impl fmt::Display for Error { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + crate::error::Formatter::from(self).fmt(f) + } +} + +impl fmt::Display for ErrorKind { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + use self::ErrorKind::*; + match *self { + CaptureLimitExceeded => write!( + f, + "exceeded the maximum number of \ + capturing groups ({})", + ::std::u32::MAX + ), + ClassEscapeInvalid => { + write!(f, "invalid escape sequence found in character class") + } + ClassRangeInvalid => write!( + f, + "invalid character class range, \ + the start must be <= the end" + ), + ClassRangeLiteral => { + write!(f, "invalid range boundary, must be a literal") + } + ClassUnclosed => write!(f, "unclosed character class"), + DecimalEmpty => write!(f, "decimal literal empty"), + DecimalInvalid => write!(f, "decimal literal invalid"), + EscapeHexEmpty => write!(f, "hexadecimal literal empty"), + EscapeHexInvalid => { + write!(f, "hexadecimal literal is not a Unicode scalar value") + } + EscapeHexInvalidDigit => write!(f, "invalid hexadecimal digit"), + EscapeUnexpectedEof => write!( + f, + "incomplete escape sequence, \ + reached end of pattern prematurely" + ), + EscapeUnrecognized => write!(f, "unrecognized escape sequence"), + FlagDanglingNegation => { + write!(f, "dangling flag negation operator") + } + FlagDuplicate { .. } => write!(f, "duplicate flag"), + FlagRepeatedNegation { .. } => { + write!(f, "flag negation operator repeated") + } + FlagUnexpectedEof => { + write!(f, "expected flag but got end of regex") + } + FlagUnrecognized => write!(f, "unrecognized flag"), + GroupNameDuplicate { .. } => { + write!(f, "duplicate capture group name") + } + GroupNameEmpty => write!(f, "empty capture group name"), + GroupNameInvalid => write!(f, "invalid capture group character"), + GroupNameUnexpectedEof => write!(f, "unclosed capture group name"), + GroupUnclosed => write!(f, "unclosed group"), + GroupUnopened => write!(f, "unopened group"), + NestLimitExceeded(limit) => write!( + f, + "exceed the maximum number of \ + nested parentheses/brackets ({})", + limit + ), + RepetitionCountInvalid => write!( + f, + "invalid repetition count range, \ + the start must be <= the end" + ), + RepetitionCountDecimalEmpty => { + write!(f, "repetition quantifier expects a valid decimal") + } + RepetitionCountUnclosed => { + write!(f, "unclosed counted repetition") + } + RepetitionMissing => { + write!(f, "repetition operator missing expression") + } + UnicodeClassInvalid => { + write!(f, "invalid Unicode character class") + } + UnsupportedBackreference => { + write!(f, "backreferences are not supported") + } + UnsupportedLookAround => write!( + f, + "look-around, including look-ahead and look-behind, \ + is not supported" + ), + _ => unreachable!(), + } + } +} + +/// Span represents the position information of a single AST item. +/// +/// All span positions are absolute byte offsets that can be used on the +/// original regular expression that was parsed. +#[derive(Clone, Copy, Eq, PartialEq)] +pub struct Span { + /// The start byte offset. + pub start: Position, + /// The end byte offset. + pub end: Position, +} + +impl fmt::Debug for Span { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "Span({:?}, {:?})", self.start, self.end) + } +} + +impl Ord for Span { + fn cmp(&self, other: &Span) -> Ordering { + (&self.start, &self.end).cmp(&(&other.start, &other.end)) + } +} + +impl PartialOrd for Span { + fn partial_cmp(&self, other: &Span) -> Option<Ordering> { + Some(self.cmp(other)) + } +} + +/// A single position in a regular expression. +/// +/// A position encodes one half of a span, and include the byte offset, line +/// number and column number. +#[derive(Clone, Copy, Eq, PartialEq)] +pub struct Position { + /// The absolute offset of this position, starting at `0` from the + /// beginning of the regular expression pattern string. + pub offset: usize, + /// The line number, starting at `1`. + pub line: usize, + /// The approximate column number, starting at `1`. + pub column: usize, +} + +impl fmt::Debug for Position { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!( + f, + "Position(o: {:?}, l: {:?}, c: {:?})", + self.offset, self.line, self.column + ) + } +} + +impl Ord for Position { + fn cmp(&self, other: &Position) -> Ordering { + self.offset.cmp(&other.offset) + } +} + +impl PartialOrd for Position { + fn partial_cmp(&self, other: &Position) -> Option<Ordering> { + Some(self.cmp(other)) + } +} + +impl Span { + /// Create a new span with the given positions. + pub fn new(start: Position, end: Position) -> Span { + Span { start, end } + } + + /// Create a new span using the given position as the start and end. + pub fn splat(pos: Position) -> Span { + Span::new(pos, pos) + } + + /// Create a new span by replacing the starting the position with the one + /// given. + pub fn with_start(self, pos: Position) -> Span { + Span { start: pos, ..self } + } + + /// Create a new span by replacing the ending the position with the one + /// given. + pub fn with_end(self, pos: Position) -> Span { + Span { end: pos, ..self } + } + + /// Returns true if and only if this span occurs on a single line. + pub fn is_one_line(&self) -> bool { + self.start.line == self.end.line + } + + /// Returns true if and only if this span is empty. That is, it points to + /// a single position in the concrete syntax of a regular expression. + pub fn is_empty(&self) -> bool { + self.start.offset == self.end.offset + } +} + +impl Position { + /// Create a new position with the given information. + /// + /// `offset` is the absolute offset of the position, starting at `0` from + /// the beginning of the regular expression pattern string. + /// + /// `line` is the line number, starting at `1`. + /// + /// `column` is the approximate column number, starting at `1`. + pub fn new(offset: usize, line: usize, column: usize) -> Position { + Position { offset, line, column } + } +} + +/// An abstract syntax tree for a singular expression along with comments +/// found. +/// +/// Comments are not stored in the tree itself to avoid complexity. Each +/// comment contains a span of precisely where it occurred in the original +/// regular expression. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct WithComments { + /// The actual ast. + pub ast: Ast, + /// All comments found in the original regular expression. + pub comments: Vec<Comment>, +} + +/// A comment from a regular expression with an associated span. +/// +/// A regular expression can only contain comments when the `x` flag is +/// enabled. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Comment { + /// The span of this comment, including the beginning `#` and ending `\n`. + pub span: Span, + /// The comment text, starting with the first character following the `#` + /// and ending with the last character preceding the `\n`. + pub comment: String, +} + +/// An abstract syntax tree for a single regular expression. +/// +/// An `Ast`'s `fmt::Display` implementation uses constant stack space and heap +/// space proportional to the size of the `Ast`. +/// +/// This type defines its own destructor that uses constant stack space and +/// heap space proportional to the size of the `Ast`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum Ast { + /// An empty regex that matches everything. + Empty(Span), + /// A set of flags, e.g., `(?is)`. + Flags(SetFlags), + /// A single character literal, which includes escape sequences. + Literal(Literal), + /// The "any character" class. + Dot(Span), + /// A single zero-width assertion. + Assertion(Assertion), + /// A single character class. This includes all forms of character classes + /// except for `.`. e.g., `\d`, `\pN`, `[a-z]` and `[[:alpha:]]`. + Class(Class), + /// A repetition operator applied to an arbitrary regular expression. + Repetition(Repetition), + /// A grouped regular expression. + Group(Group), + /// An alternation of regular expressions. + Alternation(Alternation), + /// A concatenation of regular expressions. + Concat(Concat), +} + +impl Ast { + /// Return the span of this abstract syntax tree. + pub fn span(&self) -> &Span { + match *self { + Ast::Empty(ref span) => span, + Ast::Flags(ref x) => &x.span, + Ast::Literal(ref x) => &x.span, + Ast::Dot(ref span) => span, + Ast::Assertion(ref x) => &x.span, + Ast::Class(ref x) => x.span(), + Ast::Repetition(ref x) => &x.span, + Ast::Group(ref x) => &x.span, + Ast::Alternation(ref x) => &x.span, + Ast::Concat(ref x) => &x.span, + } + } + + /// Return true if and only if this Ast is empty. + pub fn is_empty(&self) -> bool { + match *self { + Ast::Empty(_) => true, + _ => false, + } + } + + /// Returns true if and only if this AST has any (including possibly empty) + /// subexpressions. + fn has_subexprs(&self) -> bool { + match *self { + Ast::Empty(_) + | Ast::Flags(_) + | Ast::Literal(_) + | Ast::Dot(_) + | Ast::Assertion(_) => false, + Ast::Class(_) + | Ast::Repetition(_) + | Ast::Group(_) + | Ast::Alternation(_) + | Ast::Concat(_) => true, + } + } +} + +/// Print a display representation of this Ast. +/// +/// This does not preserve any of the original whitespace formatting that may +/// have originally been present in the concrete syntax from which this Ast +/// was generated. +/// +/// This implementation uses constant stack space and heap space proportional +/// to the size of the `Ast`. +impl fmt::Display for Ast { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + use crate::ast::print::Printer; + Printer::new().print(self, f) + } +} + +/// An alternation of regular expressions. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Alternation { + /// The span of this alternation. + pub span: Span, + /// The alternate regular expressions. + pub asts: Vec<Ast>, +} + +impl Alternation { + /// Return this alternation as an AST. + /// + /// If this alternation contains zero ASTs, then Ast::Empty is + /// returned. If this alternation contains exactly 1 AST, then the + /// corresponding AST is returned. Otherwise, Ast::Alternation is returned. + pub fn into_ast(mut self) -> Ast { + match self.asts.len() { + 0 => Ast::Empty(self.span), + 1 => self.asts.pop().unwrap(), + _ => Ast::Alternation(self), + } + } +} + +/// A concatenation of regular expressions. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Concat { + /// The span of this concatenation. + pub span: Span, + /// The concatenation regular expressions. + pub asts: Vec<Ast>, +} + +impl Concat { + /// Return this concatenation as an AST. + /// + /// If this concatenation contains zero ASTs, then Ast::Empty is + /// returned. If this concatenation contains exactly 1 AST, then the + /// corresponding AST is returned. Otherwise, Ast::Concat is returned. + pub fn into_ast(mut self) -> Ast { + match self.asts.len() { + 0 => Ast::Empty(self.span), + 1 => self.asts.pop().unwrap(), + _ => Ast::Concat(self), + } + } +} + +/// A single literal expression. +/// +/// A literal corresponds to a single Unicode scalar value. Literals may be +/// represented in their literal form, e.g., `a` or in their escaped form, +/// e.g., `\x61`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Literal { + /// The span of this literal. + pub span: Span, + /// The kind of this literal. + pub kind: LiteralKind, + /// The Unicode scalar value corresponding to this literal. + pub c: char, +} + +impl Literal { + /// If this literal was written as a `\x` hex escape, then this returns + /// the corresponding byte value. Otherwise, this returns `None`. + pub fn byte(&self) -> Option<u8> { + let short_hex = LiteralKind::HexFixed(HexLiteralKind::X); + if self.c as u32 <= 255 && self.kind == short_hex { + Some(self.c as u8) + } else { + None + } + } +} + +/// The kind of a single literal expression. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum LiteralKind { + /// The literal is written verbatim, e.g., `a` or `☃`. + Verbatim, + /// The literal is written as an escape because it is punctuation, e.g., + /// `\*` or `\[`. + Punctuation, + /// The literal is written as an octal escape, e.g., `\141`. + Octal, + /// The literal is written as a hex code with a fixed number of digits + /// depending on the type of the escape, e.g., `\x61` or or `\u0061` or + /// `\U00000061`. + HexFixed(HexLiteralKind), + /// The literal is written as a hex code with a bracketed number of + /// digits. The only restriction is that the bracketed hex code must refer + /// to a valid Unicode scalar value. + HexBrace(HexLiteralKind), + /// The literal is written as a specially recognized escape, e.g., `\f` + /// or `\n`. + Special(SpecialLiteralKind), +} + +/// The type of a special literal. +/// +/// A special literal is a special escape sequence recognized by the regex +/// parser, e.g., `\f` or `\n`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum SpecialLiteralKind { + /// Bell, spelled `\a` (`\x07`). + Bell, + /// Form feed, spelled `\f` (`\x0C`). + FormFeed, + /// Tab, spelled `\t` (`\x09`). + Tab, + /// Line feed, spelled `\n` (`\x0A`). + LineFeed, + /// Carriage return, spelled `\r` (`\x0D`). + CarriageReturn, + /// Vertical tab, spelled `\v` (`\x0B`). + VerticalTab, + /// Space, spelled `\ ` (`\x20`). Note that this can only appear when + /// parsing in verbose mode. + Space, +} + +/// The type of a Unicode hex literal. +/// +/// Note that all variants behave the same when used with brackets. They only +/// differ when used without brackets in the number of hex digits that must +/// follow. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum HexLiteralKind { + /// A `\x` prefix. When used without brackets, this form is limited to + /// two digits. + X, + /// A `\u` prefix. When used without brackets, this form is limited to + /// four digits. + UnicodeShort, + /// A `\U` prefix. When used without brackets, this form is limited to + /// eight digits. + UnicodeLong, +} + +impl HexLiteralKind { + /// The number of digits that must be used with this literal form when + /// used without brackets. When used with brackets, there is no + /// restriction on the number of digits. + pub fn digits(&self) -> u32 { + match *self { + HexLiteralKind::X => 2, + HexLiteralKind::UnicodeShort => 4, + HexLiteralKind::UnicodeLong => 8, + } + } +} + +/// A single character class expression. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum Class { + /// A Unicode character class, e.g., `\pL` or `\p{Greek}`. + Unicode(ClassUnicode), + /// A perl character class, e.g., `\d` or `\W`. + Perl(ClassPerl), + /// A bracketed character class set, which may contain zero or more + /// character ranges and/or zero or more nested classes. e.g., + /// `[a-zA-Z\pL]`. + Bracketed(ClassBracketed), +} + +impl Class { + /// Return the span of this character class. + pub fn span(&self) -> &Span { + match *self { + Class::Perl(ref x) => &x.span, + Class::Unicode(ref x) => &x.span, + Class::Bracketed(ref x) => &x.span, + } + } +} + +/// A Perl character class. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassPerl { + /// The span of this class. + pub span: Span, + /// The kind of Perl class. + pub kind: ClassPerlKind, + /// Whether the class is negated or not. e.g., `\d` is not negated but + /// `\D` is. + pub negated: bool, +} + +/// The available Perl character classes. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ClassPerlKind { + /// Decimal numbers. + Digit, + /// Whitespace. + Space, + /// Word characters. + Word, +} + +/// An ASCII character class. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassAscii { + /// The span of this class. + pub span: Span, + /// The kind of ASCII class. + pub kind: ClassAsciiKind, + /// Whether the class is negated or not. e.g., `[[:alpha:]]` is not negated + /// but `[[:^alpha:]]` is. + pub negated: bool, +} + +/// The available ASCII character classes. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ClassAsciiKind { + /// `[0-9A-Za-z]` + Alnum, + /// `[A-Za-z]` + Alpha, + /// `[\x00-\x7F]` + Ascii, + /// `[ \t]` + Blank, + /// `[\x00-\x1F\x7F]` + Cntrl, + /// `[0-9]` + Digit, + /// `[!-~]` + Graph, + /// `[a-z]` + Lower, + /// `[ -~]` + Print, + /// `[!-/:-@\[-`{-~]` + Punct, + /// `[\t\n\v\f\r ]` + Space, + /// `[A-Z]` + Upper, + /// `[0-9A-Za-z_]` + Word, + /// `[0-9A-Fa-f]` + Xdigit, +} + +impl ClassAsciiKind { + /// Return the corresponding ClassAsciiKind variant for the given name. + /// + /// The name given should correspond to the lowercase version of the + /// variant name. e.g., `cntrl` is the name for `ClassAsciiKind::Cntrl`. + /// + /// If no variant with the corresponding name exists, then `None` is + /// returned. + pub fn from_name(name: &str) -> Option<ClassAsciiKind> { + use self::ClassAsciiKind::*; + match name { + "alnum" => Some(Alnum), + "alpha" => Some(Alpha), + "ascii" => Some(Ascii), + "blank" => Some(Blank), + "cntrl" => Some(Cntrl), + "digit" => Some(Digit), + "graph" => Some(Graph), + "lower" => Some(Lower), + "print" => Some(Print), + "punct" => Some(Punct), + "space" => Some(Space), + "upper" => Some(Upper), + "word" => Some(Word), + "xdigit" => Some(Xdigit), + _ => None, + } + } +} + +/// A Unicode character class. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassUnicode { + /// The span of this class. + pub span: Span, + /// Whether this class is negated or not. + /// + /// Note: be careful when using this attribute. This specifically refers + /// to whether the class is written as `\p` or `\P`, where the latter + /// is `negated = true`. However, it also possible to write something like + /// `\P{scx!=Katakana}` which is actually equivalent to + /// `\p{scx=Katakana}` and is therefore not actually negated even though + /// `negated = true` here. To test whether this class is truly negated + /// or not, use the `is_negated` method. + pub negated: bool, + /// The kind of Unicode class. + pub kind: ClassUnicodeKind, +} + +impl ClassUnicode { + /// Returns true if this class has been negated. + /// + /// Note that this takes the Unicode op into account, if it's present. + /// e.g., `is_negated` for `\P{scx!=Katakana}` will return `false`. + pub fn is_negated(&self) -> bool { + match self.kind { + ClassUnicodeKind::NamedValue { + op: ClassUnicodeOpKind::NotEqual, + .. + } => !self.negated, + _ => self.negated, + } + } +} + +/// The available forms of Unicode character classes. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ClassUnicodeKind { + /// A one letter abbreviated class, e.g., `\pN`. + OneLetter(char), + /// A binary property, general category or script. The string may be + /// empty. + Named(String), + /// A property name and an associated value. + NamedValue { + /// The type of Unicode op used to associate `name` with `value`. + op: ClassUnicodeOpKind, + /// The property name (which may be empty). + name: String, + /// The property value (which may be empty). + value: String, + }, +} + +/// The type of op used in a Unicode character class. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ClassUnicodeOpKind { + /// A property set to a specific value, e.g., `\p{scx=Katakana}`. + Equal, + /// A property set to a specific value using a colon, e.g., + /// `\p{scx:Katakana}`. + Colon, + /// A property that isn't a particular value, e.g., `\p{scx!=Katakana}`. + NotEqual, +} + +impl ClassUnicodeOpKind { + /// Whether the op is an equality op or not. + pub fn is_equal(&self) -> bool { + match *self { + ClassUnicodeOpKind::Equal | ClassUnicodeOpKind::Colon => true, + _ => false, + } + } +} + +/// A bracketed character class, e.g., `[a-z0-9]`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassBracketed { + /// The span of this class. + pub span: Span, + /// Whether this class is negated or not. e.g., `[a]` is not negated but + /// `[^a]` is. + pub negated: bool, + /// The type of this set. A set is either a normal union of things, e.g., + /// `[abc]` or a result of applying set operations, e.g., `[\pL--c]`. + pub kind: ClassSet, +} + +/// A character class set. +/// +/// This type corresponds to the internal structure of a bracketed character +/// class. That is, every bracketed character is one of two types: a union of +/// items (literals, ranges, other bracketed classes) or a tree of binary set +/// operations. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ClassSet { + /// An item, which can be a single literal, range, nested character class + /// or a union of items. + Item(ClassSetItem), + /// A single binary operation (i.e., &&, -- or ~~). + BinaryOp(ClassSetBinaryOp), +} + +impl ClassSet { + /// Build a set from a union. + pub fn union(ast: ClassSetUnion) -> ClassSet { + ClassSet::Item(ClassSetItem::Union(ast)) + } + + /// Return the span of this character class set. + pub fn span(&self) -> &Span { + match *self { + ClassSet::Item(ref x) => x.span(), + ClassSet::BinaryOp(ref x) => &x.span, + } + } + + /// Return true if and only if this class set is empty. + fn is_empty(&self) -> bool { + match *self { + ClassSet::Item(ClassSetItem::Empty(_)) => true, + _ => false, + } + } +} + +/// A single component of a character class set. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum ClassSetItem { + /// An empty item. + /// + /// Note that a bracketed character class cannot contain a single empty + /// item. Empty items can appear when using one of the binary operators. + /// For example, `[&&]` is the intersection of two empty classes. + Empty(Span), + /// A single literal. + Literal(Literal), + /// A range between two literals. + Range(ClassSetRange), + /// An ASCII character class, e.g., `[:alnum:]` or `[:punct:]`. + Ascii(ClassAscii), + /// A Unicode character class, e.g., `\pL` or `\p{Greek}`. + Unicode(ClassUnicode), + /// A perl character class, e.g., `\d` or `\W`. + Perl(ClassPerl), + /// A bracketed character class set, which may contain zero or more + /// character ranges and/or zero or more nested classes. e.g., + /// `[a-zA-Z\pL]`. + Bracketed(Box<ClassBracketed>), + /// A union of items. + Union(ClassSetUnion), +} + +impl ClassSetItem { + /// Return the span of this character class set item. + pub fn span(&self) -> &Span { + match *self { + ClassSetItem::Empty(ref span) => span, + ClassSetItem::Literal(ref x) => &x.span, + ClassSetItem::Range(ref x) => &x.span, + ClassSetItem::Ascii(ref x) => &x.span, + ClassSetItem::Perl(ref x) => &x.span, + ClassSetItem::Unicode(ref x) => &x.span, + ClassSetItem::Bracketed(ref x) => &x.span, + ClassSetItem::Union(ref x) => &x.span, + } + } +} + +/// A single character class range in a set. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassSetRange { + /// The span of this range. + pub span: Span, + /// The start of this range. + pub start: Literal, + /// The end of this range. + pub end: Literal, +} + +impl ClassSetRange { + /// Returns true if and only if this character class range is valid. + /// + /// The only case where a range is invalid is if its start is greater than + /// its end. + pub fn is_valid(&self) -> bool { + self.start.c <= self.end.c + } +} + +/// A union of items inside a character class set. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassSetUnion { + /// The span of the items in this operation. e.g., the `a-z0-9` in + /// `[^a-z0-9]` + pub span: Span, + /// The sequence of items that make up this union. + pub items: Vec<ClassSetItem>, +} + +impl ClassSetUnion { + /// Push a new item in this union. + /// + /// The ending position of this union's span is updated to the ending + /// position of the span of the item given. If the union is empty, then + /// the starting position of this union is set to the starting position + /// of this item. + /// + /// In other words, if you only use this method to add items to a union + /// and you set the spans on each item correctly, then you should never + /// need to adjust the span of the union directly. + pub fn push(&mut self, item: ClassSetItem) { + if self.items.is_empty() { + self.span.start = item.span().start; + } + self.span.end = item.span().end; + self.items.push(item); + } + + /// Return this union as a character class set item. + /// + /// If this union contains zero items, then an empty union is + /// returned. If this concatenation contains exactly 1 item, then the + /// corresponding item is returned. Otherwise, ClassSetItem::Union is + /// returned. + pub fn into_item(mut self) -> ClassSetItem { + match self.items.len() { + 0 => ClassSetItem::Empty(self.span), + 1 => self.items.pop().unwrap(), + _ => ClassSetItem::Union(self), + } + } +} + +/// A Unicode character class set operation. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct ClassSetBinaryOp { + /// The span of this operation. e.g., the `a-z--[h-p]` in `[a-z--h-p]`. + pub span: Span, + /// The type of this set operation. + pub kind: ClassSetBinaryOpKind, + /// The left hand side of the operation. + pub lhs: Box<ClassSet>, + /// The right hand side of the operation. + pub rhs: Box<ClassSet>, +} + +/// The type of a Unicode character class set operation. +/// +/// Note that this doesn't explicitly represent union since there is no +/// explicit union operator. Concatenation inside a character class corresponds +/// to the union operation. +#[derive(Clone, Copy, Debug, Eq, PartialEq)] +pub enum ClassSetBinaryOpKind { + /// The intersection of two sets, e.g., `\pN&&[a-z]`. + Intersection, + /// The difference of two sets, e.g., `\pN--[0-9]`. + Difference, + /// The symmetric difference of two sets. The symmetric difference is the + /// set of elements belonging to one but not both sets. + /// e.g., `[\pL~~[:ascii:]]`. + SymmetricDifference, +} + +/// A single zero-width assertion. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Assertion { + /// The span of this assertion. + pub span: Span, + /// The assertion kind, e.g., `\b` or `^`. + pub kind: AssertionKind, +} + +/// An assertion kind. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum AssertionKind { + /// `^` + StartLine, + /// `$` + EndLine, + /// `\A` + StartText, + /// `\z` + EndText, + /// `\b` + WordBoundary, + /// `\B` + NotWordBoundary, +} + +/// A repetition operation applied to a regular expression. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Repetition { + /// The span of this operation. + pub span: Span, + /// The actual operation. + pub op: RepetitionOp, + /// Whether this operation was applied greedily or not. + pub greedy: bool, + /// The regular expression under repetition. + pub ast: Box<Ast>, +} + +/// The repetition operator itself. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct RepetitionOp { + /// The span of this operator. This includes things like `+`, `*?` and + /// `{m,n}`. + pub span: Span, + /// The type of operation. + pub kind: RepetitionKind, +} + +/// The kind of a repetition operator. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum RepetitionKind { + /// `?` + ZeroOrOne, + /// `*` + ZeroOrMore, + /// `+` + OneOrMore, + /// `{m,n}` + Range(RepetitionRange), +} + +/// A range repetition operator. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum RepetitionRange { + /// `{m}` + Exactly(u32), + /// `{m,}` + AtLeast(u32), + /// `{m,n}` + Bounded(u32, u32), +} + +impl RepetitionRange { + /// Returns true if and only if this repetition range is valid. + /// + /// The only case where a repetition range is invalid is if it is bounded + /// and its start is greater than its end. + pub fn is_valid(&self) -> bool { + match *self { + RepetitionRange::Bounded(s, e) if s > e => false, + _ => true, + } + } +} + +/// A grouped regular expression. +/// +/// This includes both capturing and non-capturing groups. This does **not** +/// include flag-only groups like `(?is)`, but does contain any group that +/// contains a sub-expression, e.g., `(a)`, `(?P<name>a)`, `(?:a)` and +/// `(?is:a)`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Group { + /// The span of this group. + pub span: Span, + /// The kind of this group. + pub kind: GroupKind, + /// The regular expression in this group. + pub ast: Box<Ast>, +} + +impl Group { + /// If this group is non-capturing, then this returns the (possibly empty) + /// set of flags. Otherwise, `None` is returned. + pub fn flags(&self) -> Option<&Flags> { + match self.kind { + GroupKind::NonCapturing(ref flags) => Some(flags), + _ => None, + } + } + + /// Returns true if and only if this group is capturing. + pub fn is_capturing(&self) -> bool { + match self.kind { + GroupKind::CaptureIndex(_) | GroupKind::CaptureName(_) => true, + GroupKind::NonCapturing(_) => false, + } + } + + /// Returns the capture index of this group, if this is a capturing group. + /// + /// This returns a capture index precisely when `is_capturing` is `true`. + pub fn capture_index(&self) -> Option<u32> { + match self.kind { + GroupKind::CaptureIndex(i) => Some(i), + GroupKind::CaptureName(ref x) => Some(x.index), + GroupKind::NonCapturing(_) => None, + } + } +} + +/// The kind of a group. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum GroupKind { + /// `(a)` + CaptureIndex(u32), + /// `(?P<name>a)` + CaptureName(CaptureName), + /// `(?:a)` and `(?i:a)` + NonCapturing(Flags), +} + +/// A capture name. +/// +/// This corresponds to the name itself between the angle brackets in, e.g., +/// `(?P<foo>expr)`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct CaptureName { + /// The span of this capture name. + pub span: Span, + /// The capture name. + pub name: String, + /// The capture index. + pub index: u32, +} + +/// A group of flags that is not applied to a particular regular expression. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct SetFlags { + /// The span of these flags, including the grouping parentheses. + pub span: Span, + /// The actual sequence of flags. + pub flags: Flags, +} + +/// A group of flags. +/// +/// This corresponds only to the sequence of flags themselves, e.g., `is-u`. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct Flags { + /// The span of this group of flags. + pub span: Span, + /// A sequence of flag items. Each item is either a flag or a negation + /// operator. + pub items: Vec<FlagsItem>, +} + +impl Flags { + /// Add the given item to this sequence of flags. + /// + /// If the item was added successfully, then `None` is returned. If the + /// given item is a duplicate, then `Some(i)` is returned, where + /// `items[i].kind == item.kind`. + pub fn add_item(&mut self, item: FlagsItem) -> Option<usize> { + for (i, x) in self.items.iter().enumerate() { + if x.kind == item.kind { + return Some(i); + } + } + self.items.push(item); + None + } + + /// Returns the state of the given flag in this set. + /// + /// If the given flag is in the set but is negated, then `Some(false)` is + /// returned. + /// + /// If the given flag is in the set and is not negated, then `Some(true)` + /// is returned. + /// + /// Otherwise, `None` is returned. + pub fn flag_state(&self, flag: Flag) -> Option<bool> { + let mut negated = false; + for x in &self.items { + match x.kind { + FlagsItemKind::Negation => { + negated = true; + } + FlagsItemKind::Flag(ref xflag) if xflag == &flag => { + return Some(!negated); + } + _ => {} + } + } + None + } +} + +/// A single item in a group of flags. +#[derive(Clone, Debug, Eq, PartialEq)] +pub struct FlagsItem { + /// The span of this item. + pub span: Span, + /// The kind of this item. + pub kind: FlagsItemKind, +} + +/// The kind of an item in a group of flags. +#[derive(Clone, Debug, Eq, PartialEq)] +pub enum FlagsItemKind { + /// A negation operator applied to all subsequent flags in the enclosing + /// group. + Negation, + /// A single flag in a group. + Flag(Flag), +} + +impl FlagsItemKind { + /// Returns true if and only if this item is a negation operator. + pub fn is_negation(&self) -> bool { + match *self { + FlagsItemKind::Negation => true, + _ => false, + } + } +} + +/// A single flag. +#[derive(Clone, Copy, Debug, Eq, PartialEq)] +pub enum Flag { + /// `i` + CaseInsensitive, + /// `m` + MultiLine, + /// `s` + DotMatchesNewLine, + /// `U` + SwapGreed, + /// `u` + Unicode, + /// `x` + IgnoreWhitespace, +} + +/// A custom `Drop` impl is used for `Ast` such that it uses constant stack +/// space but heap space proportional to the depth of the `Ast`. +impl Drop for Ast { + fn drop(&mut self) { + use std::mem; + + match *self { + Ast::Empty(_) + | Ast::Flags(_) + | Ast::Literal(_) + | Ast::Dot(_) + | Ast::Assertion(_) + // Classes are recursive, so they get their own Drop impl. + | Ast::Class(_) => return, + Ast::Repetition(ref x) if !x.ast.has_subexprs() => return, + Ast::Group(ref x) if !x.ast.has_subexprs() => return, + Ast::Alternation(ref x) if x.asts.is_empty() => return, + Ast::Concat(ref x) if x.asts.is_empty() => return, + _ => {} + } + + let empty_span = || Span::splat(Position::new(0, 0, 0)); + let empty_ast = || Ast::Empty(empty_span()); + let mut stack = vec![mem::replace(self, empty_ast())]; + while let Some(mut ast) = stack.pop() { + match ast { + Ast::Empty(_) + | Ast::Flags(_) + | Ast::Literal(_) + | Ast::Dot(_) + | Ast::Assertion(_) + // Classes are recursive, so they get their own Drop impl. + | Ast::Class(_) => {} + Ast::Repetition(ref mut x) => { + stack.push(mem::replace(&mut x.ast, empty_ast())); + } + Ast::Group(ref mut x) => { + stack.push(mem::replace(&mut x.ast, empty_ast())); + } + Ast::Alternation(ref mut x) => { + stack.extend(x.asts.drain(..)); + } + Ast::Concat(ref mut x) => { + stack.extend(x.asts.drain(..)); + } + } + } + } +} + +/// A custom `Drop` impl is used for `ClassSet` such that it uses constant +/// stack space but heap space proportional to the depth of the `ClassSet`. +impl Drop for ClassSet { + fn drop(&mut self) { + use std::mem; + + match *self { + ClassSet::Item(ref item) => match *item { + ClassSetItem::Empty(_) + | ClassSetItem::Literal(_) + | ClassSetItem::Range(_) + | ClassSetItem::Ascii(_) + | ClassSetItem::Unicode(_) + | ClassSetItem::Perl(_) => return, + ClassSetItem::Bracketed(ref x) => { + if x.kind.is_empty() { + return; + } + } + ClassSetItem::Union(ref x) => { + if x.items.is_empty() { + return; + } + } + }, + ClassSet::BinaryOp(ref op) => { + if op.lhs.is_empty() && op.rhs.is_empty() { + return; + } + } + } + + let empty_span = || Span::splat(Position::new(0, 0, 0)); + let empty_set = || ClassSet::Item(ClassSetItem::Empty(empty_span())); + let mut stack = vec![mem::replace(self, empty_set())]; + while let Some(mut set) = stack.pop() { + match set { + ClassSet::Item(ref mut item) => match *item { + ClassSetItem::Empty(_) + | ClassSetItem::Literal(_) + | ClassSetItem::Range(_) + | ClassSetItem::Ascii(_) + | ClassSetItem::Unicode(_) + | ClassSetItem::Perl(_) => {} + ClassSetItem::Bracketed(ref mut x) => { + stack.push(mem::replace(&mut x.kind, empty_set())); + } + ClassSetItem::Union(ref mut x) => { + stack.extend(x.items.drain(..).map(ClassSet::Item)); + } + }, + ClassSet::BinaryOp(ref mut op) => { + stack.push(mem::replace(&mut op.lhs, empty_set())); + stack.push(mem::replace(&mut op.rhs, empty_set())); + } + } + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + + // We use a thread with an explicit stack size to test that our destructor + // for Ast can handle arbitrarily sized expressions in constant stack + // space. In case we run on a platform without threads (WASM?), we limit + // this test to Windows/Unix. + #[test] + #[cfg(any(unix, windows))] + fn no_stack_overflow_on_drop() { + use std::thread; + + let run = || { + let span = || Span::splat(Position::new(0, 0, 0)); + let mut ast = Ast::Empty(span()); + for i in 0..200 { + ast = Ast::Group(Group { + span: span(), + kind: GroupKind::CaptureIndex(i), + ast: Box::new(ast), + }); + } + assert!(!ast.is_empty()); + }; + + // We run our test on a thread with a small stack size so we can + // force the issue more easily. + thread::Builder::new() + .stack_size(1 << 10) + .spawn(run) + .unwrap() + .join() + .unwrap(); + } +} |