mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 11:03:16 +00:00
386 lines
15 KiB
Rust
386 lines
15 KiB
Rust
#![allow(cast_possible_truncation)]
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use rustc::lint::LateContext;
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use rustc::hir::def::{Def, PathResolution};
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use rustc_const_eval::lookup_const_by_id;
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use rustc_const_math::{ConstInt, ConstUsize, ConstIsize};
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use rustc::hir::*;
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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::ops::Deref;
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use std::rc::Rc;
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use syntax::ast::{FloatTy, LitIntType, LitKind, StrStyle, UintTy, IntTy};
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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 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.to_u64().expect("negative constant can't be casted to u64")
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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, cast_possible_wrap)]
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pub fn as_float(&self) -> Option<f64> {
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match *self {
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Constant::Float(ref s, _) => s.parse().ok(),
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Constant::Int(i) if i.is_negative() => Some(i.to_u64_unchecked() as i64 as f64),
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Constant::Int(i) => Some(i.to_u64_unchecked() as f64),
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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 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_u64_unchecked() == r.to_u64_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 {
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mem::transmute::<f64, u64>(l) == mem::transmute::<f64, u64>(r)
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},
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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_u64_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)) => 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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_ => 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(lit: &LitKind) -> Constant {
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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(value, LitIntType::Unsuffixed) => Constant::Int(ConstInt::Infer(value)),
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LitKind::Int(value, LitIntType::Unsigned(UintTy::U8)) => Constant::Int(ConstInt::U8(value as u8)),
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LitKind::Int(value, LitIntType::Unsigned(UintTy::U16)) => Constant::Int(ConstInt::U16(value as u16)),
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LitKind::Int(value, LitIntType::Unsigned(UintTy::U32)) => Constant::Int(ConstInt::U32(value as u32)),
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LitKind::Int(value, LitIntType::Unsigned(UintTy::U64)) => Constant::Int(ConstInt::U64(value as u64)),
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LitKind::Int(value, LitIntType::Unsigned(UintTy::Us)) => {
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Constant::Int(ConstInt::Usize(ConstUsize::Us32(value as u32)))
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}
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LitKind::Int(value, LitIntType::Signed(IntTy::I8)) => Constant::Int(ConstInt::I8(value as i8)),
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LitKind::Int(value, LitIntType::Signed(IntTy::I16)) => Constant::Int(ConstInt::I16(value as i16)),
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LitKind::Int(value, LitIntType::Signed(IntTy::I32)) => Constant::Int(ConstInt::I32(value as i32)),
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LitKind::Int(value, LitIntType::Signed(IntTy::I64)) => Constant::Int(ConstInt::I64(value as i64)),
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LitKind::Int(value, LitIntType::Signed(IntTy::Is)) => {
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Constant::Int(ConstInt::Isize(ConstIsize::Is32(value as i32)))
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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: 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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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, _ty)) = lookup_const_by_id(lcx.tcx, id, 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(|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> {
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if let Some(Constant::Bool(b)) = self.expr(cond) {
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if b {
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self.block(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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fn binop_apply<F>(&mut self, left: &Expr, right: &Expr, op: F) -> Option<Constant>
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where F: Fn(Constant, Constant) -> Option<Constant>
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{
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if let (Some(lc), Some(rc)) = (self.expr(left), self.expr(right)) {
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op(lc, rc)
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} else {
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None
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}
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}
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}
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