Neg/Pos enum for discriminant sign
diff --git a/syntax/discriminant.rs b/syntax/discriminant.rs
index 5e39f63..80f7c0b 100644
--- a/syntax/discriminant.rs
+++ b/syntax/discriminant.rs
@@ -16,10 +16,16 @@
#[derive(Copy, Clone, Eq, PartialEq)]
pub struct Discriminant {
- negative: bool,
+ sign: Sign,
magnitude: u64,
}
+#[derive(Copy, Clone, Eq, PartialEq)]
+enum Sign {
+ Negative,
+ Positive,
+}
+
impl DiscriminantSet {
pub fn new(repr: Option<Atom>) -> Self {
DiscriminantSet {
@@ -59,21 +65,23 @@
pub fn insert_next(&mut self) -> Result<Discriminant> {
let discriminant = match self.previous {
None => Discriminant::zero(),
- Some(mut discriminant) if discriminant.negative => {
- discriminant.magnitude -= 1;
- if discriminant.magnitude == 0 {
- discriminant.negative = false;
+ Some(mut discriminant) => match discriminant.sign {
+ Sign::Negative => {
+ discriminant.magnitude -= 1;
+ if discriminant.magnitude == 0 {
+ discriminant.sign = Sign::Positive;
+ }
+ discriminant
}
- discriminant
- }
- Some(mut discriminant) => {
- if discriminant.magnitude == u64::MAX {
- let msg = format!("discriminant overflow on value after {}", u64::MAX);
- return Err(Error::new(Span::call_site(), msg));
+ Sign::Positive => {
+ if discriminant.magnitude == u64::MAX {
+ let msg = format!("discriminant overflow on value after {}", u64::MAX);
+ return Err(Error::new(Span::call_site(), msg));
+ }
+ discriminant.magnitude += 1;
+ discriminant
}
- discriminant.magnitude += 1;
- discriminant
- }
+ },
};
insert(self, discriminant)
}
@@ -109,7 +117,10 @@
Expr::Unary(unary) => {
if let UnOp::Neg(_) = unary.op {
let (mut discriminant, repr) = expr_to_discriminant(&unary.expr)?;
- discriminant.negative ^= true;
+ discriminant.sign = match discriminant.sign {
+ Sign::Positive => Sign::Negative,
+ Sign::Negative => Sign::Positive,
+ };
return Ok((discriminant, repr));
}
}
@@ -141,21 +152,25 @@
impl Discriminant {
const fn zero() -> Self {
Discriminant {
- negative: false,
+ sign: Sign::Positive,
magnitude: 0,
}
}
const fn pos(u: u64) -> Self {
Discriminant {
- negative: false,
+ sign: Sign::Positive,
magnitude: u,
}
}
const fn neg(i: i64) -> Self {
Discriminant {
- negative: i < 0,
+ sign: if i < 0 {
+ Sign::Negative
+ } else {
+ Sign::Positive
+ },
// This is `i.abs() as u64` but without overflow on MIN. Uses the
// fact that MIN.wrapping_abs() wraps back to MIN whose binary
// representation is 1<<63, and thus the `as u64` conversion
@@ -168,7 +183,7 @@
impl Display for Discriminant {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- if self.negative {
+ if self.sign == Sign::Negative {
f.write_str("-")?;
}
Display::fmt(&self.magnitude, f)
@@ -177,7 +192,7 @@
impl ToTokens for Discriminant {
fn to_tokens(&self, tokens: &mut TokenStream) {
- if self.negative {
+ if self.sign == Sign::Negative {
Token).to_tokens(tokens);
}
Literal::u64_unsuffixed(self.magnitude).to_tokens(tokens);
@@ -188,15 +203,14 @@
type Err = Error;
fn from_str(mut s: &str) -> Result<Self> {
- let negative = s.starts_with('-');
- if negative {
+ let sign = if s.starts_with('-') {
s = &s[1..];
- }
+ Sign::Negative
+ } else {
+ Sign::Positive
+ };
match s.parse::<u64>() {
- Ok(magnitude) => Ok(Discriminant {
- negative,
- magnitude,
- }),
+ Ok(magnitude) => Ok(Discriminant { sign, magnitude }),
Err(_) => Err(Error::new(
Span::call_site(),
"discriminant value outside of supported range",
@@ -207,11 +221,12 @@
impl Ord for Discriminant {
fn cmp(&self, other: &Self) -> Ordering {
- match (self.negative, other.negative) {
- (true, true) => self.magnitude.cmp(&other.magnitude).reverse(),
- (true, false) => Ordering::Less, // negative < positive
- (false, true) => Ordering::Greater, // positive > negative
- (false, false) => self.magnitude.cmp(&other.magnitude),
+ use self::Sign::{Negative, Positive};
+ match (self.sign, other.sign) {
+ (Negative, Negative) => self.magnitude.cmp(&other.magnitude).reverse(),
+ (Negative, Positive) => Ordering::Less, // negative < positive
+ (Positive, Negative) => Ordering::Greater, // positive > negative
+ (Positive, Positive) => self.magnitude.cmp(&other.magnitude),
}
}
}