rustc-ap-syntax_pos 128.0.0

// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! An "interner" is a data structure that associates values with usize tags and
//! allows bidirectional lookup; i.e. given a value, one can easily find the
//! type, and vice versa.

use hygiene::SyntaxContext;
use {Span, DUMMY_SP, GLOBALS};

use rustc_data_structures::fx::FxHashMap;
use serialize::{Decodable, Decoder, Encodable, Encoder};
use std::fmt;
use std::cmp::{PartialEq, Ordering, PartialOrd, Ord};
use std::hash::{Hash, Hasher};

#[derive(Copy, Clone, Eq)]
pub struct Ident {
    pub name: Symbol,
    pub span: Span,
}

impl Ident {
    #[inline]
    pub const fn new(name: Symbol, span: Span) -> Ident {
        Ident { name, span }
    }
    #[inline]
    pub const fn with_empty_ctxt(name: Symbol) -> Ident {
        Ident::new(name, DUMMY_SP)
    }

    /// Maps an interned string to an identifier with an empty syntax context.
    pub fn from_interned_str(string: InternedString) -> Ident {
        Ident::with_empty_ctxt(string.as_symbol())
    }

    /// Maps a string to an identifier with an empty syntax context.
    pub fn from_str(string: &str) -> Ident {
        Ident::with_empty_ctxt(Symbol::intern(string))
    }

    /// Replace `lo` and `hi` with those from `span`, but keep hygiene context.
    pub fn with_span_pos(self, span: Span) -> Ident {
        Ident::new(self.name, span.with_ctxt(self.span.ctxt()))
    }

    pub fn without_first_quote(self) -> Ident {
        Ident::new(Symbol::intern(self.name.as_str().trim_left_matches('\'')), self.span)
    }

    pub fn modern(self) -> Ident {
        Ident::new(self.name, self.span.modern())
    }

    pub fn gensym(self) -> Ident {
        Ident::new(self.name.gensymed(), self.span)
    }
}

impl PartialEq for Ident {
    fn eq(&self, rhs: &Self) -> bool {
        self.name == rhs.name && self.span.ctxt() == rhs.span.ctxt()
    }
}

impl Hash for Ident {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.name.hash(state);
        self.span.ctxt().hash(state);
    }
}

impl fmt::Debug for Ident {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}{:?}", self.name, self.span.ctxt())
    }
}

impl fmt::Display for Ident {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(&self.name, f)
    }
}

impl Encodable for Ident {
    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
        if self.span.ctxt().modern() == SyntaxContext::empty() {
            s.emit_str(&self.name.as_str())
        } else { // FIXME(jseyfried) intercrate hygiene
            let mut string = "#".to_owned();
            string.push_str(&self.name.as_str());
            s.emit_str(&string)
        }
    }
}

impl Decodable for Ident {
    fn decode<D: Decoder>(d: &mut D) -> Result<Ident, D::Error> {
        let string = d.read_str()?;
        Ok(if !string.starts_with('#') {
            Ident::from_str(&string)
        } else { // FIXME(jseyfried) intercrate hygiene
            Ident::with_empty_ctxt(Symbol::gensym(&string[1..]))
        })
    }
}

/// A symbol is an interned or gensymed string.
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Symbol(u32);

// The interner is pointed to by a thread local value which is only set on the main thread
// with parallelization is disabled. So we don't allow Symbol to transfer between threads
// to avoid panics and other errors, even though it would be memory safe to do so.
#[cfg(not(parallel_queries))]
impl !Send for Symbol { }
#[cfg(not(parallel_queries))]
impl !Sync for Symbol { }

impl Symbol {
    /// Maps a string to its interned representation.
    pub fn intern(string: &str) -> Self {
        with_interner(|interner| interner.intern(string))
    }

    pub fn interned(self) -> Self {
        with_interner(|interner| interner.interned(self))
    }

    /// gensym's a new usize, using the current interner.
    pub fn gensym(string: &str) -> Self {
        with_interner(|interner| interner.gensym(string))
    }

    pub fn gensymed(self) -> Self {
        with_interner(|interner| interner.gensymed(self))
    }

    pub fn as_str(self) -> LocalInternedString {
        with_interner(|interner| unsafe {
            LocalInternedString {
                string: ::std::mem::transmute::<&str, &str>(interner.get(self))
            }
        })
    }

    pub fn as_interned_str(self) -> InternedString {
        with_interner(|interner| InternedString {
            symbol: interner.interned(self)
        })
    }

    pub fn as_u32(self) -> u32 {
        self.0
    }
}

impl fmt::Debug for Symbol {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let is_gensymed = with_interner(|interner| interner.is_gensymed(*self));
        if is_gensymed {
            write!(f, "{}({})", self, self.0)
        } else {
            write!(f, "{}", self)
        }
    }
}

impl fmt::Display for Symbol {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(&self.as_str(), f)
    }
}

impl Encodable for Symbol {
    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
        s.emit_str(&self.as_str())
    }
}

impl Decodable for Symbol {
    fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error> {
        Ok(Symbol::intern(&d.read_str()?))
    }
}

impl<T: ::std::ops::Deref<Target=str>> PartialEq<T> for Symbol {
    fn eq(&self, other: &T) -> bool {
        self.as_str() == other.deref()
    }
}

#[derive(Default)]
pub struct Interner {
    names: FxHashMap<Box<str>, Symbol>,
    strings: Vec<Box<str>>,
    gensyms: Vec<Symbol>,
}

impl Interner {
    pub fn new() -> Self {
        Interner::default()
    }

    fn prefill(init: &[&str]) -> Self {
        let mut this = Interner::new();
        for &string in init {
            this.intern(string);
        }
        this
    }

    pub fn intern(&mut self, string: &str) -> Symbol {
        if let Some(&name) = self.names.get(string) {
            return name;
        }

        let name = Symbol(self.strings.len() as u32);
        let string = string.to_string().into_boxed_str();
        self.strings.push(string.clone());
        self.names.insert(string, name);
        name
    }

    pub fn interned(&self, symbol: Symbol) -> Symbol {
        if (symbol.0 as usize) < self.strings.len() {
            symbol
        } else {
            self.interned(self.gensyms[(!0 - symbol.0) as usize])
        }
    }

    fn gensym(&mut self, string: &str) -> Symbol {
        let symbol = self.intern(string);
        self.gensymed(symbol)
    }

    fn gensymed(&mut self, symbol: Symbol) -> Symbol {
        self.gensyms.push(symbol);
        Symbol(!0 - self.gensyms.len() as u32 + 1)
    }

    fn is_gensymed(&mut self, symbol: Symbol) -> bool {
        symbol.0 as usize >= self.strings.len()
    }

    pub fn get(&self, symbol: Symbol) -> &str {
        match self.strings.get(symbol.0 as usize) {
            Some(ref string) => string,
            None => self.get(self.gensyms[(!0 - symbol.0) as usize]),
        }
    }
}

// In this macro, there is the requirement that the name (the number) must be monotonically
// increasing by one in the special identifiers, starting at 0; the same holds for the keywords,
// except starting from the next number instead of zero.
macro_rules! declare_keywords {(
    $( ($index: expr, $konst: ident, $string: expr) )*
) => {
    pub mod keywords {
        use super::{Symbol, Ident};
        #[derive(Clone, Copy, PartialEq, Eq)]
        pub struct Keyword {
            ident: Ident,
        }
        impl Keyword {
            #[inline] pub fn ident(self) -> Ident { self.ident }
            #[inline] pub fn name(self) -> Symbol { self.ident.name }
        }
        $(
            #[allow(non_upper_case_globals)]
            pub const $konst: Keyword = Keyword {
                ident: Ident::with_empty_ctxt(super::Symbol($index))
            };
        )*
    }

    impl Interner {
        pub fn fresh() -> Self {
            Interner::prefill(&[$($string,)*])
        }
    }
}}

// NB: leaving holes in the ident table is bad! a different ident will get
// interned with the id from the hole, but it will be between the min and max
// of the reserved words, and thus tagged as "reserved".
// After modifying this list adjust `is_special_ident`, `is_used_keyword`/`is_unused_keyword`,
// this should be rarely necessary though if the keywords are kept in alphabetic order.
declare_keywords! {
    // Special reserved identifiers used internally for elided lifetimes,
    // unnamed method parameters, crate root module, error recovery etc.
    (0,  Invalid,            "")
    (1,  CrateRoot,          "{{root}}")
    (2,  DollarCrate,        "$crate")
    (3,  Underscore,         "_")

    // Keywords used in the language.
    (4,  As,                 "as")
    (5,  Box,                "box")
    (6,  Break,              "break")
    (7,  Const,              "const")
    (8,  Continue,           "continue")
    (9,  Crate,              "crate")
    (10, Else,               "else")
    (11, Enum,               "enum")
    (12, Extern,             "extern")
    (13, False,              "false")
    (14, Fn,                 "fn")
    (15, For,                "for")
    (16, If,                 "if")
    (17, Impl,               "impl")
    (18, In,                 "in")
    (19, Let,                "let")
    (20, Loop,               "loop")
    (21, Match,              "match")
    (22, Mod,                "mod")
    (23, Move,               "move")
    (24, Mut,                "mut")
    (25, Pub,                "pub")
    (26, Ref,                "ref")
    (27, Return,             "return")
    (28, SelfValue,          "self")
    (29, SelfType,           "Self")
    (30, Static,             "static")
    (31, Struct,             "struct")
    (32, Super,              "super")
    (33, Trait,              "trait")
    (34, True,               "true")
    (35, Type,               "type")
    (36, Unsafe,             "unsafe")
    (37, Use,                "use")
    (38, Where,              "where")
    (39, While,              "while")

    // Keywords reserved for future use.
    (40, Abstract,           "abstract")
    (41, Alignof,            "alignof")
    (42, Become,             "become")
    (43, Do,                 "do")
    (44, Final,              "final")
    (45, Macro,              "macro")
    (46, Offsetof,           "offsetof")
    (47, Override,           "override")
    (48, Priv,               "priv")
    (49, Pure,               "pure")
    (50, Sizeof,             "sizeof")
    (51, Typeof,             "typeof")
    (52, Unsized,            "unsized")
    (53, Virtual,            "virtual")
    (54, Yield,              "yield")

    // Special lifetime names
    (55, UnderscoreLifetime, "'_")
    (56, StaticLifetime,     "'static")

    // Weak keywords, have special meaning only in specific contexts.
    (57, Auto,               "auto")
    (58, Catch,              "catch")
    (59, Default,            "default")
    (60, Dyn,                "dyn")
    (61, Union,              "union")
}

// If an interner exists, return it. Otherwise, prepare a fresh one.
#[inline]
fn with_interner<T, F: FnOnce(&mut Interner) -> T>(f: F) -> T {
    GLOBALS.with(|globals| f(&mut *globals.symbol_interner.lock()))
}

/// Represents a string stored in the interner. Because the interner outlives any thread
/// which uses this type, we can safely treat `string` which points to interner data,
/// as an immortal string, as long as this type never crosses between threads.
// FIXME: Ensure that the interner outlives any thread which uses LocalInternedString,
//        by creating a new thread right after constructing the interner
#[derive(Clone, Copy, Hash, PartialOrd, Eq, Ord)]
pub struct LocalInternedString {
    string: &'static str,
}

impl LocalInternedString {
    pub fn as_interned_str(self) -> InternedString {
        InternedString {
            symbol: Symbol::intern(self.string)
        }
    }
}

impl<U: ?Sized> ::std::convert::AsRef<U> for LocalInternedString
where
    str: ::std::convert::AsRef<U>
{
    fn as_ref(&self) -> &U {
        self.string.as_ref()
    }
}

impl<T: ::std::ops::Deref<Target = str>> ::std::cmp::PartialEq<T> for LocalInternedString {
    fn eq(&self, other: &T) -> bool {
        self.string == other.deref()
    }
}

impl ::std::cmp::PartialEq<LocalInternedString> for str {
    fn eq(&self, other: &LocalInternedString) -> bool {
        self == other.string
    }
}

impl<'a> ::std::cmp::PartialEq<LocalInternedString> for &'a str {
    fn eq(&self, other: &LocalInternedString) -> bool {
        *self == other.string
    }
}

impl ::std::cmp::PartialEq<LocalInternedString> for String {
    fn eq(&self, other: &LocalInternedString) -> bool {
        self == other.string
    }
}

impl<'a> ::std::cmp::PartialEq<LocalInternedString> for &'a String {
    fn eq(&self, other: &LocalInternedString) -> bool {
        *self == other.string
    }
}

impl !Send for LocalInternedString {}
impl !Sync for LocalInternedString {}

impl ::std::ops::Deref for LocalInternedString {
    type Target = str;
    fn deref(&self) -> &str { self.string }
}

impl fmt::Debug for LocalInternedString {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(self.string, f)
    }
}

impl fmt::Display for LocalInternedString {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        fmt::Display::fmt(self.string, f)
    }
}

impl Decodable for LocalInternedString {
    fn decode<D: Decoder>(d: &mut D) -> Result<LocalInternedString, D::Error> {
        Ok(Symbol::intern(&d.read_str()?).as_str())
    }
}

impl Encodable for LocalInternedString {
    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
        s.emit_str(self.string)
    }
}

/// Represents a string stored in the string interner
#[derive(Clone, Copy, Eq)]
pub struct InternedString {
    symbol: Symbol,
}

impl InternedString {
    pub fn with<F: FnOnce(&str) -> R, R>(self, f: F) -> R {
        let str = with_interner(|interner| {
            interner.get(self.symbol) as *const str
        });
        // This is safe because the interner keeps string alive until it is dropped.
        // We can access it because we know the interner is still alive since we use a
        // scoped thread local to access it, and it was alive at the begining of this scope
        unsafe { f(&*str) }
    }

    pub fn as_symbol(self) -> Symbol {
        self.symbol
    }

    pub fn as_str(self) -> LocalInternedString {
        self.symbol.as_str()
    }
}

impl Hash for InternedString {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.with(|str| str.hash(state))
    }
}

impl PartialOrd<InternedString> for InternedString {
    fn partial_cmp(&self, other: &InternedString) -> Option<Ordering> {
        if self.symbol == other.symbol {
            return Some(Ordering::Equal);
        }
        self.with(|self_str| other.with(|other_str| self_str.partial_cmp(&other_str)))
    }
}

impl Ord for InternedString {
    fn cmp(&self, other: &InternedString) -> Ordering {
        if self.symbol == other.symbol {
            return Ordering::Equal;
        }
        self.with(|self_str| other.with(|other_str| self_str.cmp(&other_str)))
    }
}

impl<T: ::std::ops::Deref<Target = str>> PartialEq<T> for InternedString {
    fn eq(&self, other: &T) -> bool {
        self.with(|string| string == other.deref())
    }
}

impl PartialEq<InternedString> for InternedString {
    fn eq(&self, other: &InternedString) -> bool {
        self.symbol == other.symbol
    }
}

impl PartialEq<InternedString> for str {
    fn eq(&self, other: &InternedString) -> bool {
        other.with(|string| self == string)
    }
}

impl<'a> PartialEq<InternedString> for &'a str {
    fn eq(&self, other: &InternedString) -> bool {
        other.with(|string| *self == string)
    }
}

impl PartialEq<InternedString> for String {
    fn eq(&self, other: &InternedString) -> bool {
        other.with(|string| self == string)
    }
}

impl<'a> PartialEq<InternedString> for &'a String {
    fn eq(&self, other: &InternedString) -> bool {
        other.with(|string| *self == string)
    }
}

impl ::std::convert::From<InternedString> for String {
    fn from(val: InternedString) -> String {
        val.as_symbol().to_string()
    }
}

impl fmt::Debug for InternedString {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.with(|str| fmt::Debug::fmt(&str, f))
    }
}

impl fmt::Display for InternedString {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.with(|str| fmt::Display::fmt(&str, f))
    }
}

impl Decodable for InternedString {
    fn decode<D: Decoder>(d: &mut D) -> Result<InternedString, D::Error> {
        Ok(Symbol::intern(&d.read_str()?).as_interned_str())
    }
}

impl Encodable for InternedString {
    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
        self.with(|string| s.emit_str(string))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use Globals;

    #[test]
    fn interner_tests() {
        let mut i: Interner = Interner::new();
        // first one is zero:
        assert_eq!(i.intern("dog"), Symbol(0));
        // re-use gets the same entry:
        assert_eq!(i.intern("dog"), Symbol(0));
        // different string gets a different #:
        assert_eq!(i.intern("cat"), Symbol(1));
        assert_eq!(i.intern("cat"), Symbol(1));
        // dog is still at zero
        assert_eq!(i.intern("dog"), Symbol(0));
        assert_eq!(i.gensym("zebra"), Symbol(4294967295));
        // gensym of same string gets new number :
        assert_eq!(i.gensym("zebra"), Symbol(4294967294));
        // gensym of *existing* string gets new number:
        assert_eq!(i.gensym("dog"), Symbol(4294967293));
    }

    #[test]
    fn without_first_quote_test() {
        GLOBALS.set(&Globals::new(), || {
            let i = Ident::from_str("'break");
            assert_eq!(i.without_first_quote().name, keywords::Break.name());
        });
    }
}