mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-14 23:32:43 +00:00
377 lines
14 KiB
Rust
377 lines
14 KiB
Rust
#![allow(cast_possible_truncation)]
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use rustc::lint::LateContext;
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use rustc::hir::def::Def;
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use rustc_const_eval::lookup_const_by_id;
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use rustc_const_math::ConstInt;
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use rustc::hir::*;
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use rustc::ty::{self, TyCtxt};
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use rustc::ty::subst::{Substs, Subst};
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use std::cmp::Ordering::{self, Equal};
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use std::cmp::PartialOrd;
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use std::hash::{Hash, Hasher};
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use std::mem;
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use std::rc::Rc;
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use syntax::ast::{FloatTy, LitKind, StrStyle, NodeId};
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use syntax::ptr::P;
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#[derive(Debug, Copy, Clone)]
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pub enum FloatWidth {
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F32,
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F64,
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Any,
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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::F32 => FloatWidth::F32,
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FloatTy::F64 => FloatWidth::F64,
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}
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}
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}
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/// A `LitKind`-like enum to fold constant `Expr`s into.
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#[derive(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 char 'a'
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Char(char),
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/// an integer, third argument is whether the value is negated
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Int(ConstInt),
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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 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 l_sty), &Constant::Str(ref rs, ref r_sty)) => ls == rs && l_sty == r_sty,
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(&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
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(&Constant::Char(l), &Constant::Char(r)) => l == r,
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(&Constant::Int(l), &Constant::Int(r)) => {
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l.is_negative() == r.is_negative() && l.to_u128_unchecked() == r.to_u128_unchecked()
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},
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(&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
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// we want `Fw32 == FwAny` and `FwAny == Fw64`, by transitivity we must have
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// `Fw32 == Fw64` so don’t compare them
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match (ls.parse::<f64>(), rs.parse::<f64>()) {
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// mem::transmute is required to catch non-matching 0.0, -0.0, and NaNs
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(Ok(l), Ok(r)) => unsafe { mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r) },
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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 Hash for Constant {
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fn hash<H>(&self, state: &mut H)
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where H: Hasher
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{
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match *self {
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Constant::Str(ref s, ref k) => {
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s.hash(state);
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k.hash(state);
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},
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Constant::Binary(ref b) => {
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b.hash(state);
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},
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Constant::Char(c) => {
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c.hash(state);
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},
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Constant::Int(i) => {
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i.to_u128_unchecked().hash(state);
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i.is_negative().hash(state);
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},
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Constant::Float(ref f, _) => {
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// don’t use the width here because of PartialEq implementation
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if let Ok(f) = f.parse::<f64>() {
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unsafe { mem::transmute::<f64, u64>(f) }.hash(state);
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}
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},
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Constant::Bool(b) => {
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b.hash(state);
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},
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Constant::Vec(ref v) |
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Constant::Tuple(ref v) => {
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v.hash(state);
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},
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Constant::Repeat(ref c, l) => {
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c.hash(state);
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l.hash(state);
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},
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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 l_sty), &Constant::Str(ref rs, ref r_sty)) => {
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if l_sty == r_sty {
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Some(ls.cmp(rs))
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} else {
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None
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}
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},
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(&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)),
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(&Constant::Int(l), &Constant::Int(r)) => Some(l.cmp(&r)),
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(&Constant::Float(ref ls, _), &Constant::Float(ref rs, _)) => {
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match (ls.parse::<f64>(), rs.parse::<f64>()) {
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(Ok(ref l), Ok(ref r)) => {
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match (l.partial_cmp(r), l.is_sign_positive() == r.is_sign_positive()) {
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// Check for comparison of -0.0 and 0.0
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(Some(Ordering::Equal), false) => None,
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(x, _) => x,
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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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(&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)),
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(&Constant::Tuple(ref l), &Constant::Tuple(ref 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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_ => 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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/// parse a `LitKind` to a `Constant`
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#[allow(cast_possible_wrap)]
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pub fn lit_to_constant<'a, 'tcx>(lit: &LitKind, tcx: TyCtxt<'a, 'tcx, 'tcx>, mut ty: ty::Ty<'tcx>) -> Constant {
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use syntax::ast::*;
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use syntax::ast::LitIntType::*;
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use rustc::ty::util::IntTypeExt;
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if let ty::TyAdt(adt, _) = ty.sty {
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if adt.is_enum() {
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ty = adt.repr.discr_type().to_ty(tcx)
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}
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}
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match *lit {
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LitKind::Str(ref is, style) => Constant::Str(is.to_string(), style),
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LitKind::Byte(b) => Constant::Int(ConstInt::U8(b)),
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LitKind::ByteStr(ref s) => Constant::Binary(s.clone()),
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LitKind::Char(c) => Constant::Char(c),
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LitKind::Int(n, hint) => {
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match (&ty.sty, hint) {
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(&ty::TyInt(ity), _) |
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(_, Signed(ity)) => {
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Constant::Int(ConstInt::new_signed_truncating(n as i128, ity, tcx.sess.target.int_type))
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},
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(&ty::TyUint(uty), _) |
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(_, Unsigned(uty)) => {
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Constant::Int(ConstInt::new_unsigned_truncating(n as u128, uty, tcx.sess.target.uint_type))
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},
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_ => bug!(),
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}
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},
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LitKind::Float(ref is, ty) => Constant::Float(is.to_string(), ty.into()),
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LitKind::FloatUnsuffixed(ref is) => Constant::Float(is.to_string(), FloatWidth::Any),
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LitKind::Bool(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 self::Constant::*;
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match *o {
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Bool(b) => Some(Bool(!b)),
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Int(value) => (!value).ok().map(Int),
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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 self::Constant::*;
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match o {
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Int(value) => (-value).ok().map(Int),
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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_float_str(s: &str) -> 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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pub fn constant(lcx: &LateContext, e: &Expr) -> Option<(Constant, bool)> {
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let mut cx = ConstEvalLateContext {
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tcx: lcx.tcx,
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tables: lcx.tables,
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needed_resolution: false,
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substs: lcx.tcx.intern_substs(&[]),
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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(lcx: &LateContext, e: &Expr) -> Option<Constant> {
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constant(lcx, e).and_then(|(cst, res)| if res { None } else { Some(cst) })
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}
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struct ConstEvalLateContext<'a, 'tcx: 'a> {
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tcx: TyCtxt<'a, 'tcx, 'tcx>,
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tables: &'a ty::TypeckTables<'tcx>,
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needed_resolution: bool,
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substs: &'tcx Substs<'tcx>,
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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(ref qpath) => self.fetch_path(qpath, e.id),
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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, self.tcx, self.tables.expr_ty(e))),
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ExprArray(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, _) => {
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let n = match self.tables.expr_ty(e).sty {
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ty::TyArray(_, n) => n,
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_ => span_bug!(e.span, "typeck error"),
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};
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self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
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},
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ExprUnary(op, ref operand) => {
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self.expr(operand).and_then(|o| 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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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(&mut self, vec: &[Expr]) -> 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, qpath: &QPath, id: NodeId) -> Option<Constant> {
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let def = self.tables.qpath_def(qpath, id);
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match def {
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Def::Const(def_id) |
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Def::AssociatedConst(def_id) => {
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let substs = self.tables
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.node_id_item_substs(id)
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.unwrap_or_else(|| self.tcx.intern_substs(&[]));
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let substs = if self.substs.is_empty() {
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substs
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} else {
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substs.subst(self.tcx, self.substs)
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};
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if let Some((def_id, substs)) = lookup_const_by_id(self.tcx, def_id, substs) {
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let mut cx = ConstEvalLateContext {
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tcx: self.tcx,
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tables: self.tcx.typeck_tables_of(def_id),
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needed_resolution: false,
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substs: substs,
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};
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let body = if let Some(id) = self.tcx.hir.as_local_node_id(def_id) {
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self.tcx.mir_const_qualif(def_id);
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self.tcx.hir.body(self.tcx.hir.body_owned_by(id))
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} else {
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self.tcx.sess.cstore.item_body(self.tcx, def_id)
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};
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let ret = cx.expr(&body.value);
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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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}
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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(|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: &P<Expr>, otherwise: &Option<P<Expr>>) -> Option<Constant> {
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if let Some(Constant::Bool(b)) = self.expr(cond) {
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if b {
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self.expr(&**then)
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} else {
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otherwise.as_ref().and_then(|expr| self.expr(expr))
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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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fn binop(&mut self, op: BinOp, left: &Expr, right: &Expr) -> Option<Constant> {
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let l = if let Some(l) = self.expr(left) {
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l
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} else {
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return None;
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};
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let r = self.expr(right);
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match (op.node, l, r) {
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(BiAdd, Constant::Int(l), Some(Constant::Int(r))) => (l + r).ok().map(Constant::Int),
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(BiSub, Constant::Int(l), Some(Constant::Int(r))) => (l - r).ok().map(Constant::Int),
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(BiMul, Constant::Int(l), Some(Constant::Int(r))) => (l * r).ok().map(Constant::Int),
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(BiDiv, Constant::Int(l), Some(Constant::Int(r))) => (l / r).ok().map(Constant::Int),
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(BiRem, Constant::Int(l), Some(Constant::Int(r))) => (l % r).ok().map(Constant::Int),
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(BiAnd, Constant::Bool(false), _) => Some(Constant::Bool(false)),
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(BiOr, Constant::Bool(true), _) => Some(Constant::Bool(true)),
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(BiAnd, Constant::Bool(true), Some(r)) |
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(BiOr, Constant::Bool(false), Some(r)) => Some(r),
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(BiBitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
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(BiBitXor, Constant::Int(l), Some(Constant::Int(r))) => (l ^ r).ok().map(Constant::Int),
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(BiBitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
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(BiBitAnd, Constant::Int(l), Some(Constant::Int(r))) => (l & r).ok().map(Constant::Int),
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(BiBitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
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(BiBitOr, Constant::Int(l), Some(Constant::Int(r))) => (l | r).ok().map(Constant::Int),
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(BiShl, Constant::Int(l), Some(Constant::Int(r))) => (l << r).ok().map(Constant::Int),
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(BiShr, Constant::Int(l), Some(Constant::Int(r))) => (l >> r).ok().map(Constant::Int),
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(BiEq, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l == r)),
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(BiNe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l != r)),
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(BiLt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l < r)),
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(BiLe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l <= r)),
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(BiGe, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l >= r)),
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(BiGt, Constant::Int(l), Some(Constant::Int(r))) => Some(Constant::Bool(l > r)),
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_ => None,
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}
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}
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}
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