644 lines
23 KiB
Rust
644 lines
23 KiB
Rust
#![allow(cast_possible_truncation)]
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use rustc::lint::LateContext;
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use rustc::middle::const_eval::lookup_const_by_id;
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use rustc::middle::def::PathResolution;
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use rustc::middle::def::Def;
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use rustc_front::hir::*;
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use syntax::ptr::P;
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use std::char;
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use std::cmp::PartialOrd;
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use std::cmp::Ordering::{self, Greater, Less, Equal};
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use std::rc::Rc;
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use std::ops::Deref;
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use std::fmt;
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use syntax::ast::Lit_;
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use syntax::ast::LitIntType;
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use syntax::ast::{UintTy, FloatTy, StrStyle};
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use syntax::ast::Sign::{self, Plus, Minus};
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#[derive(PartialEq, Eq, Debug, Copy, Clone)]
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pub enum FloatWidth {
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Fw32,
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Fw64,
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FwAny,
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}
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impl From<FloatTy> for FloatWidth {
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fn from(ty: FloatTy) -> FloatWidth {
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match ty {
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FloatTy::TyF32 => FloatWidth::Fw32,
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FloatTy::TyF64 => FloatWidth::Fw64,
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}
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}
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}
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/// a Lit_-like enum to fold constant `Expr`s into
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#[derive(Eq, Debug, Clone)]
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pub enum Constant {
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/// a String "abc"
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Str(String, StrStyle),
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/// a Binary String b"abc"
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Binary(Rc<Vec<u8>>),
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/// a single byte b'a'
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Byte(u8),
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/// a single char 'a'
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Char(char),
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/// an integer
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Int(u64, LitIntType),
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/// a float with given type
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Float(String, FloatWidth),
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/// true or false
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Bool(bool),
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/// an array of constants
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Vec(Vec<Constant>),
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/// also an array, but with only one constant, repeated N times
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Repeat(Box<Constant>, usize),
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/// a tuple of constants
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Tuple(Vec<Constant>),
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}
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impl Constant {
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/// convert to u64 if possible
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///
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/// # panics
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///
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/// if the constant could not be converted to u64 losslessly
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fn as_u64(&self) -> u64 {
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if let Constant::Int(val, _) = *self {
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val // TODO we may want to check the sign if any
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} else {
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panic!("Could not convert a {:?} to u64", self);
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}
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}
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/// convert this constant to a f64, if possible
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#[allow(cast_precision_loss)]
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pub fn as_float(&self) -> Option<f64> {
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match *self {
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Constant::Byte(b) => Some(b as f64),
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Constant::Float(ref s, _) => s.parse().ok(),
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Constant::Int(i, ty) => {
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Some(if is_negative(ty) {
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-(i as f64)
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} else {
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i as f64
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})
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}
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_ => None,
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}
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}
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}
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impl PartialEq for Constant {
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fn eq(&self, other: &Constant) -> bool {
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match (self, other) {
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(&Constant::Str(ref ls, ref lsty), &Constant::Str(ref rs, ref rsty)) => ls == rs && lsty == rsty,
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(&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
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(&Constant::Byte(l), &Constant::Byte(r)) => l == r,
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(&Constant::Char(l), &Constant::Char(r)) => l == r,
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(&Constant::Int(lv, lty), &Constant::Int(rv, rty)) => {
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lv == rv && (is_negative(lty) & (lv != 0)) == (is_negative(rty) & (rv != 0))
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}
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(&Constant::Float(ref ls, lw), &Constant::Float(ref rs, rw)) => {
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use self::FloatWidth::*;
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if match (lw, rw) {
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(FwAny, _) | (_, FwAny) | (Fw32, Fw32) | (Fw64, Fw64) => true,
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_ => false,
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} {
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match (ls.parse::<f64>(), rs.parse::<f64>()) {
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(Ok(l), Ok(r)) => l.eq(&r),
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_ => false,
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}
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} else {
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false
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}
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}
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(&Constant::Bool(l), &Constant::Bool(r)) => l == r,
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(&Constant::Vec(ref l), &Constant::Vec(ref r)) => l == r,
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(&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
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(&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l == r,
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_ => false, //TODO: Are there inter-type equalities?
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}
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}
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}
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impl PartialOrd for Constant {
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fn partial_cmp(&self, other: &Constant) -> Option<Ordering> {
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match (self, other) {
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(&Constant::Str(ref ls, ref lsty), &Constant::Str(ref rs, ref rsty)) => {
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if lsty != rsty {
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None
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} else {
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Some(ls.cmp(rs))
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}
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}
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(&Constant::Byte(ref l), &Constant::Byte(ref r)) => Some(l.cmp(r)),
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(&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)),
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(&Constant::Int(ref lv, lty), &Constant::Int(ref rv, rty)) => {
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Some(match (is_negative(lty) && *lv != 0, is_negative(rty) && *rv != 0) {
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(true, true) => rv.cmp(lv),
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(false, false) => lv.cmp(rv),
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(true, false) => Less,
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(false, true) => Greater,
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})
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}
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(&Constant::Float(ref ls, lw), &Constant::Float(ref rs, rw)) => {
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use self::FloatWidth::*;
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if match (lw, rw) {
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(FwAny, _) | (_, FwAny) | (Fw32, Fw32) | (Fw64, Fw64) => true,
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_ => false,
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} {
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match (ls.parse::<f64>(), rs.parse::<f64>()) {
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(Ok(ref l), Ok(ref r)) => l.partial_cmp(r),
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_ => None,
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}
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} else {
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None
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}
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}
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(&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)),
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(&Constant::Vec(ref l), &Constant::Vec(ref r)) => l.partial_cmp(&r),
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(&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => {
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match lv.partial_cmp(rv) {
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Some(Equal) => Some(ls.cmp(rs)),
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x => x,
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}
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}
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(&Constant::Tuple(ref l), &Constant::Tuple(ref r)) => l.partial_cmp(r),
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_ => None, //TODO: Are there any useful inter-type orderings?
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}
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}
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}
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fn format_byte(fmt: &mut fmt::Formatter, b: u8) -> fmt::Result {
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if b == b'\\' {
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write!(fmt, "\\\\")
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} else if 0x20 <= b && b <= 0x7e {
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write!(fmt, "{}", char::from_u32(b as u32).expect("all u8 are valid char"))
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} else if b == 0x0a {
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write!(fmt, "\\n")
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} else if b == 0x0d {
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write!(fmt, "\\r")
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} else {
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write!(fmt, "\\x{:02x}", b)
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}
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}
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impl fmt::Display for Constant {
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fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
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match *self {
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Constant::Str(ref s, _) => write!(fmt, "{:?}", s),
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Constant::Byte(ref b) => {
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write!(fmt, "b'")
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.and_then(|_| format_byte(fmt, *b))
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.and_then(|_| write!(fmt, "'"))
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}
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Constant::Binary(ref bs) => {
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try!(write!(fmt, "b\""));
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for b in bs.iter() {
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try!(format_byte(fmt, *b));
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}
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write!(fmt, "\"")
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}
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Constant::Char(ref c) => write!(fmt, "'{}'", c),
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Constant::Int(ref i, ref ity) => {
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let (sign, suffix) = match *ity {
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LitIntType::SignedIntLit(ref sity, ref sign) => {
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(if let Sign::Minus = *sign {
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"-"
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} else {
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""
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},
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sity.ty_to_string())
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}
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LitIntType::UnsignedIntLit(ref uity) => ("", uity.ty_to_string()),
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LitIntType::UnsuffixedIntLit(ref sign) => {
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(if let Sign::Minus = *sign {
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"-"
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} else {
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""
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},
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"".into())
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}
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};
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write!(fmt, "{}{}{}", sign, i, suffix)
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}
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Constant::Float(ref s, ref fw) => {
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let suffix = match *fw {
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FloatWidth::Fw32 => "f32",
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FloatWidth::Fw64 => "f64",
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FloatWidth::FwAny => "",
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};
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write!(fmt, "{}{}", s, suffix)
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}
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Constant::Bool(ref b) => write!(fmt, "{}", b),
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Constant::Repeat(ref c, ref n) => write!(fmt, "[{}; {}]", c, n),
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Constant::Vec(ref v) => {
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write!(fmt,
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"[{}]",
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v.iter()
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.map(|i| format!("{}", i))
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.collect::<Vec<_>>()
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.join(", "))
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}
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Constant::Tuple(ref t) => {
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write!(fmt,
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"({})",
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t.iter()
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.map(|i| format!("{}", i))
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.collect::<Vec<_>>()
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.join(", "))
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}
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}
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}
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}
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fn lit_to_constant(lit: &Lit_) -> Constant {
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match *lit {
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Lit_::LitStr(ref is, style) => Constant::Str(is.to_string(), style),
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Lit_::LitByte(b) => Constant::Byte(b),
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Lit_::LitByteStr(ref s) => Constant::Binary(s.clone()),
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Lit_::LitChar(c) => Constant::Char(c),
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Lit_::LitInt(value, ty) => Constant::Int(value, ty),
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Lit_::LitFloat(ref is, ty) => Constant::Float(is.to_string(), ty.into()),
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Lit_::LitFloatUnsuffixed(ref is) => Constant::Float(is.to_string(), FloatWidth::FwAny),
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Lit_::LitBool(b) => Constant::Bool(b),
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}
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}
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fn constant_not(o: Constant) -> Option<Constant> {
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use syntax::ast::LitIntType::*;
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use self::Constant::*;
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match o {
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Bool(b) => Some(Bool(!b)),
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Int(::std::u64::MAX, SignedIntLit(_, Plus)) => None,
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Int(value, SignedIntLit(ity, Plus)) => Some(Int(value + 1, SignedIntLit(ity, Minus))),
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Int(0, SignedIntLit(ity, Minus)) => Some(Int(1, SignedIntLit(ity, Minus))),
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Int(value, SignedIntLit(ity, Minus)) => Some(Int(value - 1, SignedIntLit(ity, Plus))),
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Int(value, UnsignedIntLit(ity)) => {
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let mask = match ity {
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UintTy::TyU8 => ::std::u8::MAX as u64,
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UintTy::TyU16 => ::std::u16::MAX as u64,
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UintTy::TyU32 => ::std::u32::MAX as u64,
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UintTy::TyU64 => ::std::u64::MAX,
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UintTy::TyUs => {
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return None;
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} // refuse to guess
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};
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Some(Int(!value & mask, UnsignedIntLit(ity)))
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},
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_ => None,
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}
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}
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fn constant_negate(o: Constant) -> Option<Constant> {
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use syntax::ast::LitIntType::*;
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use self::Constant::*;
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match o {
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Int(value, SignedIntLit(ity, sign)) => Some(Int(value, SignedIntLit(ity, neg_sign(sign)))),
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Int(value, UnsuffixedIntLit(sign)) => Some(Int(value, UnsuffixedIntLit(neg_sign(sign)))),
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Float(is, ty) => Some(Float(neg_float_str(is), ty)),
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_ => None,
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}
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}
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fn neg_sign(s: Sign) -> Sign {
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match s {
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Sign::Plus => Sign::Minus,
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Sign::Minus => Sign::Plus,
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}
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}
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fn neg_float_str(s: String) -> String {
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if s.starts_with('-') {
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s[1..].to_owned()
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} else {
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format!("-{}", s)
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}
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}
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/// is the given LitIntType negative?
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///
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/// Examples
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///
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/// ```
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/// assert!(is_negative(UnsuffixedIntLit(Minus)));
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/// ```
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pub fn is_negative(ty: LitIntType) -> bool {
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match ty {
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LitIntType::SignedIntLit(_, sign) | LitIntType::UnsuffixedIntLit(sign) => sign == Minus,
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LitIntType::UnsignedIntLit(_) => false,
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}
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}
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fn unify_int_type(l: LitIntType, r: LitIntType, s: Sign) -> Option<LitIntType> {
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use syntax::ast::LitIntType::*;
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match (l, r) {
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(SignedIntLit(lty, _), SignedIntLit(rty, _)) => {
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if lty == rty {
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Some(SignedIntLit(lty, s))
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} else {
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None
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}
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}
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(UnsignedIntLit(lty), UnsignedIntLit(rty)) => {
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if s == Plus && lty == rty {
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Some(UnsignedIntLit(lty))
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} else {
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None
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}
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}
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(UnsuffixedIntLit(_), UnsuffixedIntLit(_)) => Some(UnsuffixedIntLit(s)),
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(SignedIntLit(lty, _), UnsuffixedIntLit(_)) => Some(SignedIntLit(lty, s)),
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(UnsignedIntLit(lty), UnsuffixedIntLit(rs)) => {
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if rs == Plus {
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Some(UnsignedIntLit(lty))
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} else {
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None
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}
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}
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(UnsuffixedIntLit(_), SignedIntLit(rty, _)) => Some(SignedIntLit(rty, s)),
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(UnsuffixedIntLit(ls), UnsignedIntLit(rty)) => {
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if ls == Plus {
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Some(UnsignedIntLit(rty))
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} else {
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None
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}
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}
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_ => None,
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}
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}
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fn add_neg_int(pos: u64, pty: LitIntType, neg: u64, nty: LitIntType) -> Option<Constant> {
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if neg > pos {
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unify_int_type(nty, pty, Minus).map(|ty| Constant::Int(neg - pos, ty))
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} else {
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unify_int_type(nty, pty, Plus).map(|ty| Constant::Int(pos - neg, ty))
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}
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}
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fn sub_int(l: u64, lty: LitIntType, r: u64, rty: LitIntType, neg: bool) -> Option<Constant> {
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unify_int_type(lty,
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rty,
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if neg {
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Minus
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} else {
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Plus
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})
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.and_then(|ty| l.checked_sub(r).map(|v| Constant::Int(v, ty)))
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}
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pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> {
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let mut cx = ConstEvalLateContext {
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lcx: Some(lcx),
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needed_resolution: false,
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};
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cx.expr(e).map(|cst| (cst, cx.needed_resolution))
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}
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pub fn constant_simple(e: &Expr) -> Option<Constant> {
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let mut cx = ConstEvalLateContext {
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lcx: None,
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needed_resolution: false,
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};
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cx.expr(e)
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}
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struct ConstEvalLateContext<'c, 'cc: 'c> {
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lcx: Option<&'c LateContext<'c, 'cc>>,
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needed_resolution: bool,
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}
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impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
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/// simple constant folding: Insert an expression, get a constant or none.
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fn expr(&mut self, e: &Expr) -> Option<Constant> {
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match e.node {
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ExprPath(_, _) => self.fetch_path(e),
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ExprBlock(ref block) => self.block(block),
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ExprIf(ref cond, ref then, ref otherwise) => self.ifthenelse(cond, then, otherwise),
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ExprLit(ref lit) => Some(lit_to_constant(&lit.node)),
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ExprVec(ref vec) => self.multi(vec).map(Constant::Vec),
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ExprTup(ref tup) => self.multi(tup).map(Constant::Tuple),
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ExprRepeat(ref value, ref number) => {
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self.binop_apply(value, number, |v, n| Some(Constant::Repeat(Box::new(v), n.as_u64() as usize)))
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}
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ExprUnary(op, ref operand) => {
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self.expr(operand).and_then(|o| {
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match op {
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UnNot => constant_not(o),
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UnNeg => constant_negate(o),
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UnDeref => Some(o),
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}
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})
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}
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ExprBinary(op, ref left, ref right) => self.binop(op, left, right),
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// TODO: add other expressions
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_ => None,
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}
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}
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/// create `Some(Vec![..])` of all constants, unless there is any
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/// non-constant part
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fn multi<E: Deref<Target = Expr> + Sized>(&mut self, vec: &[E]) -> Option<Vec<Constant>> {
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vec.iter()
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.map(|elem| self.expr(elem))
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.collect::<Option<_>>()
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}
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/// lookup a possibly constant expression from a ExprPath
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fn fetch_path(&mut self, e: &Expr) -> Option<Constant> {
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if let Some(lcx) = self.lcx {
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let mut maybe_id = None;
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if let Some(&PathResolution { base_def: Def::Const(id), ..}) = lcx.tcx.def_map.borrow().get(&e.id) {
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maybe_id = Some(id);
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}
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// separate if lets to avoid double borrowing the def_map
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if let Some(id) = maybe_id {
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if let Some(const_expr) = lookup_const_by_id(lcx.tcx, id, None, None) {
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let ret = self.expr(const_expr);
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if ret.is_some() {
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self.needed_resolution = true;
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}
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return ret;
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}
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}
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}
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None
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}
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/// A block can only yield a constant if it only has one constant expression
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fn block(&mut self, block: &Block) -> Option<Constant> {
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if block.stmts.is_empty() {
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block.expr.as_ref().and_then(|ref b| self.expr(b))
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} else {
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None
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}
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}
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fn ifthenelse(&mut self, cond: &Expr, then: &Block, otherwise: &Option<P<Expr>>) -> Option<Constant> {
|
|
if let Some(Constant::Bool(b)) = self.expr(cond) {
|
|
if b {
|
|
self.block(then)
|
|
} else {
|
|
otherwise.as_ref().and_then(|expr| self.expr(expr))
|
|
}
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> {
|
|
match op.node {
|
|
BiAdd => {
|
|
self.binop_apply(left, right, |l, r| {
|
|
match (l, r) {
|
|
(Constant::Byte(l8), Constant::Byte(r8)) => l8.checked_add(r8).map(Constant::Byte),
|
|
(Constant::Int(l64, lty), Constant::Int(r64, rty)) => {
|
|
let (ln, rn) = (is_negative(lty), is_negative(rty));
|
|
if ln == rn {
|
|
unify_int_type(lty,
|
|
rty,
|
|
if ln {
|
|
Minus
|
|
} else {
|
|
Plus
|
|
})
|
|
.and_then(|ty| l64.checked_add(r64).map(|v| Constant::Int(v, ty)))
|
|
} else if ln {
|
|
add_neg_int(r64, rty, l64, lty)
|
|
} else {
|
|
add_neg_int(l64, lty, r64, rty)
|
|
}
|
|
}
|
|
// TODO: float (would need bignum library?)
|
|
_ => None,
|
|
}
|
|
})
|
|
}
|
|
BiSub => {
|
|
self.binop_apply(left, right, |l, r| {
|
|
match (l, r) {
|
|
(Constant::Byte(l8), Constant::Byte(r8)) => {
|
|
if r8 > l8 {
|
|
None
|
|
} else {
|
|
Some(Constant::Byte(l8 - r8))
|
|
}
|
|
}
|
|
(Constant::Int(l64, lty), Constant::Int(r64, rty)) => {
|
|
match (is_negative(lty), is_negative(rty)) {
|
|
(false, false) => sub_int(l64, lty, r64, rty, r64 > l64),
|
|
(true, true) => sub_int(l64, lty, r64, rty, l64 > r64),
|
|
(true, false) => {
|
|
unify_int_type(lty, rty, Minus)
|
|
.and_then(|ty| l64.checked_add(r64).map(|v| Constant::Int(v, ty)))
|
|
}
|
|
(false, true) => {
|
|
unify_int_type(lty, rty, Plus)
|
|
.and_then(|ty| l64.checked_add(r64).map(|v| Constant::Int(v, ty)))
|
|
}
|
|
}
|
|
}
|
|
_ => None,
|
|
}
|
|
})
|
|
}
|
|
BiMul => self.divmul(left, right, u64::checked_mul),
|
|
BiDiv => self.divmul(left, right, u64::checked_div),
|
|
// BiRem,
|
|
BiAnd => self.short_circuit(left, right, false),
|
|
BiOr => self.short_circuit(left, right, true),
|
|
BiBitXor => self.bitop(left, right, |x, y| x ^ y),
|
|
BiBitAnd => self.bitop(left, right, |x, y| x & y),
|
|
BiBitOr => self.bitop(left, right, |x, y| (x | y)),
|
|
BiShl => self.bitop(left, right, |x, y| x << y),
|
|
BiShr => self.bitop(left, right, |x, y| x >> y),
|
|
BiEq => self.binop_apply(left, right, |l, r| Some(Constant::Bool(l == r))),
|
|
BiNe => self.binop_apply(left, right, |l, r| Some(Constant::Bool(l != r))),
|
|
BiLt => self.cmp(left, right, Less, true),
|
|
BiLe => self.cmp(left, right, Greater, false),
|
|
BiGe => self.cmp(left, right, Less, false),
|
|
BiGt => self.cmp(left, right, Greater, true),
|
|
_ => None,
|
|
}
|
|
}
|
|
|
|
fn divmul<F>(&mut self, left: &Expr, right: &Expr, f: F) -> Option<Constant>
|
|
where F: Fn(u64, u64) -> Option<u64>
|
|
{
|
|
self.binop_apply(left, right, |l, r| {
|
|
match (l, r) {
|
|
(Constant::Int(l64, lty), Constant::Int(r64, rty)) => {
|
|
f(l64, r64).and_then(|value| {
|
|
unify_int_type(lty,
|
|
rty,
|
|
if is_negative(lty) == is_negative(rty) {
|
|
Plus
|
|
} else {
|
|
Minus
|
|
})
|
|
.map(|ty| Constant::Int(value, ty))
|
|
})
|
|
}
|
|
_ => None,
|
|
}
|
|
})
|
|
}
|
|
|
|
fn bitop<F>(&mut self, left: &Expr, right: &Expr, f: F) -> Option<Constant>
|
|
where F: Fn(u64, u64) -> u64
|
|
{
|
|
self.binop_apply(left, right, |l, r| {
|
|
match (l, r) {
|
|
(Constant::Bool(l), Constant::Bool(r)) => Some(Constant::Bool(f(l as u64, r as u64) != 0)),
|
|
(Constant::Byte(l8), Constant::Byte(r8)) => Some(Constant::Byte(f(l8 as u64, r8 as u64) as u8)),
|
|
(Constant::Int(l, lty), Constant::Int(r, rty)) => {
|
|
unify_int_type(lty, rty, Plus).map(|ty| Constant::Int(f(l, r), ty))
|
|
}
|
|
_ => None,
|
|
}
|
|
})
|
|
}
|
|
|
|
fn cmp(&mut self, left: &Expr, right: &Expr, ordering: Ordering, b: bool) -> Option<Constant> {
|
|
self.binop_apply(left,
|
|
right,
|
|
|l, r| l.partial_cmp(&r).map(|o| Constant::Bool(b == (o == ordering))))
|
|
}
|
|
|
|
fn binop_apply<F>(&mut self, left: &Expr, right: &Expr, op: F) -> Option<Constant>
|
|
where F: Fn(Constant, Constant) -> Option<Constant>
|
|
{
|
|
if let (Some(lc), Some(rc)) = (self.expr(left), self.expr(right)) {
|
|
op(lc, rc)
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
fn short_circuit(&mut self, left: &Expr, right: &Expr, b: bool) -> Option<Constant> {
|
|
self.expr(left).and_then(|left| {
|
|
if let Constant::Bool(lbool) = left {
|
|
if lbool == b {
|
|
Some(left)
|
|
} else {
|
|
self.expr(right).and_then(|right| {
|
|
if let Constant::Bool(_) = right {
|
|
Some(right)
|
|
} else {
|
|
None
|
|
}
|
|
})
|
|
}
|
|
} else {
|
|
None
|
|
}
|
|
})
|
|
}
|
|
}
|