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use syntax::ast::{self, Ast};
use syntax::ast::parse::Parser;
/// The results of analyzing a regex for cased literals.
#[derive(Clone, Debug, Default)]
pub struct Cased {
/// True if and only if a literal uppercase character occurs in the regex.
///
/// A regex like `\pL` contains no uppercase literals, even though `L`
/// is uppercase and the `\pL` class contains uppercase characters.
pub any_uppercase: bool,
/// True if and only if the regex contains any literal at all. A regex like
/// `\pL` has this set to false.
pub any_literal: bool,
}
impl Cased {
/// Returns a `Cased` value by doing analysis on the AST of `pattern`.
///
/// If `pattern` is not a valid regular expression, then `None` is
/// returned.
pub fn from_pattern(pattern: &str) -> Option<Cased> {
Parser::new()
.parse(pattern)
.map(|ast| Cased::from_ast(&ast))
.ok()
}
fn from_ast(ast: &Ast) -> Cased {
let mut cased = Cased::default();
cased.from_ast_impl(ast);
cased
}
fn from_ast_impl(&mut self, ast: &Ast) {
if self.done() {
return;
}
match *ast {
Ast::Empty(_)
| Ast::Flags(_)
| Ast::Dot(_)
| Ast::Assertion(_)
| Ast::Class(ast::Class::Unicode(_))
| Ast::Class(ast::Class::Perl(_)) => {}
Ast::Literal(ref x) => {
self.from_ast_literal(x);
}
Ast::Class(ast::Class::Bracketed(ref x)) => {
self.from_ast_class_set(&x.kind);
}
Ast::Repetition(ref x) => {
self.from_ast_impl(&x.ast);
}
Ast::Group(ref x) => {
self.from_ast_impl(&x.ast);
}
Ast::Alternation(ref alt) => {
for x in &alt.asts {
self.from_ast_impl(x);
}
}
Ast::Concat(ref alt) => {
for x in &alt.asts {
self.from_ast_impl(x);
}
}
}
}
fn from_ast_class_set(&mut self, ast: &ast::ClassSet) {
if self.done() {
return;
}
match *ast {
ast::ClassSet::Item(ref item) => {
self.from_ast_class_set_item(item);
}
ast::ClassSet::BinaryOp(ref x) => {
self.from_ast_class_set(&x.lhs);
self.from_ast_class_set(&x.rhs);
}
}
}
fn from_ast_class_set_item(&mut self, ast: &ast::ClassSetItem) {
if self.done() {
return;
}
match *ast {
ast::ClassSetItem::Empty(_)
| ast::ClassSetItem::Ascii(_)
| ast::ClassSetItem::Unicode(_)
| ast::ClassSetItem::Perl(_) => {}
ast::ClassSetItem::Literal(ref x) => {
self.from_ast_literal(x);
}
ast::ClassSetItem::Range(ref x) => {
self.from_ast_literal(&x.start);
self.from_ast_literal(&x.end);
}
ast::ClassSetItem::Bracketed(ref x) => {
self.from_ast_class_set(&x.kind);
}
ast::ClassSetItem::Union(ref union) => {
for x in &union.items {
self.from_ast_class_set_item(x);
}
}
}
}
fn from_ast_literal(&mut self, ast: &ast::Literal) {
self.any_literal = true;
self.any_uppercase = self.any_uppercase || ast.c.is_uppercase();
}
/// Returns true if and only if the attributes can never change no matter
/// what other AST it might see.
fn done(&self) -> bool {
self.any_uppercase && self.any_literal
}
}
#[cfg(test)]
mod tests {
use super::*;
fn cased(pattern: &str) -> Cased {
Cased::from_pattern(pattern).unwrap()
}
#[test]
fn various() {
let x = cased("");
assert!(!x.any_uppercase);
assert!(!x.any_literal);
let x = cased("foo");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased("Foo");
assert!(x.any_uppercase);
assert!(x.any_literal);
let x = cased("foO");
assert!(x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo\\");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo\w");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo\S");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo\p{Ll}");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo[a-z]");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo[A-Z]");
assert!(x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo[\S\t]");
assert!(!x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"foo\\S");
assert!(x.any_uppercase);
assert!(x.any_literal);
let x = cased(r"\p{Ll}");
assert!(!x.any_uppercase);
assert!(!x.any_literal);
let x = cased(r"aBc\w");
assert!(x.any_uppercase);
assert!(x.any_literal);
}
}
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