Enum ErrorKind

Variants

CaptureLimitExceeded

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.

ClassEscapeInvalid

An invalid escape sequence was found in a character class set.

ClassRangeInvalid

An invalid character class range was found. An invalid range is any range where the start is greater than the end.

ClassRangeLiteral

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.

ClassUnclosed

An opening [ was found with no corresponding closing ].

DecimalEmpty

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.

DecimalInvalid

An invalid decimal number was given where one was expected.

EscapeHexEmpty

A bracketed hex literal was empty.

EscapeHexInvalid

A bracketed hex literal did not correspond to a Unicode scalar value.

EscapeHexInvalidDigit

An invalid hexadecimal digit was found.

EscapeUnexpectedEof

EOF was found before an escape sequence was completed.

EscapeUnrecognized

An unrecognized escape sequence.

FlagDanglingNegation

A dangling negation was used when setting flags, e.g., i-.

FlagDuplicate { original: Span }

A flag was used twice, e.g., i-i.

FlagRepeatedNegation { original: Span }

The negation operator was used twice, e.g., -i-s.

FlagUnexpectedEof

Expected a flag but got EOF, e.g., (?.

FlagUnrecognized

Unrecognized flag, e.g., a.

GroupNameDuplicate { original: Span }

A duplicate capture name was found.

GroupNameEmpty

A capture group name is empty, e.g., (?P<>abc).

GroupNameInvalid

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).

GroupNameUnexpectedEof

A closing > could not be found for a capture group name.

GroupUnclosed

An unclosed group, e.g., (ab.

The span of this error corresponds to the unclosed parenthesis.

GroupUnopened

An unopened group, e.g., ab).

NestLimitExceeded(u32)

The nest limit was exceeded. The limit stored here is the limit configured in the parser.

RepetitionCountInvalid

The range provided in a counted repetition operator is invalid. The range is invalid if the start is greater than the end.

RepetitionCountDecimalEmpty

An opening { was not followed by a valid decimal value. For example, x{} or x{]} would fail.

RepetitionCountUnclosed

An opening { was found with no corresponding closing }.

RepetitionMissing

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.

SpecialWordBoundaryUnclosed

The special word boundary syntax, \b{something}, was used, but either EOF without } was seen, or an invalid character in the braces was seen.

SpecialWordBoundaryUnrecognized

The special word boundary syntax, \b{something}, was used, but something was not recognized as a valid word boundary kind.

SpecialWordOrRepetitionUnexpectedEof

The syntax \b{ was observed, but afterwards the end of the pattern was observed without being able to tell whether it was meant to be a bounded repetition on the \b or the beginning of a special word boundary assertion.

UnicodeClassInvalid

The Unicode class is not valid. This typically occurs when a \p is followed by something other than a {.

UnsupportedBackreference

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.

UnsupportedLookAround

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.