Remove SpanlessEq 🎃

The new solution is slightly hacky, but way more flexible. All types that implement PartialEq can now be compared spanlessly in tests by manipulating a thread-local boolean that is read in Span's PartialEq implementation.

src/syntax/span.rs

@@ -3,9 +3,23 @@
 use std::fmt::{self, Debug, Formatter};
 use std::ops::{Add, Sub};
 
+#[cfg(test)]
+use std::cell::Cell;
+
 #[cfg(feature = "serialize")]
 use serde::Serialize;
 
+#[cfg(test)]
+thread_local! {
+    static CMP_SPANS: Cell<bool> = Cell::new(true);
+}
+
+/// When set to `false` comparisons with `PartialEq` ignore spans.
+#[cfg(test)]
+pub(crate) fn set_cmp(cmp: bool) {
+    CMP_SPANS.with(|cell| cell.set(cmp));
+}
+
 /// Span offsetting.
 pub trait Offset {
     /// Offset all spans contained in `Self` by the given position.
@@ -85,7 +99,7 @@ impl<T: Debug> Debug for Spanned<T> {
 }
 
 /// Locates a slice of source code.
-#[derive(Copy, Clone, Eq, PartialEq, Hash)]
+#[derive(Copy, Clone, Hash)]
 #[cfg_attr(feature = "serialize", derive(Serialize))]
 pub struct Span {
     /// The inclusive start position.
@@ -131,6 +145,19 @@ impl Offset for Span {
     }
 }
 
+impl Eq for Span {}
+
+impl PartialEq for Span {
+    fn eq(&self, other: &Self) -> bool {
+        #[cfg(test)]
+        if !CMP_SPANS.with(Cell::get) {
+            return true;
+        }
+
+        self.start == other.start && self.end == other.end
+    }
+}
+
 impl Debug for Span {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         write!(f, "<{:?}-{:?}>", self.start, self.end)

src/syntax/test.rs

@@ -1,19 +1,18 @@
 use std::fmt::Debug;
 
 use crate::func::prelude::*;
-use super::decoration::Decoration;
-use super::expr::{Expr, Ident, NamedTuple, Object, Pair, Tuple};
-use super::parsing::{FuncArg, FuncArgs};
-use super::span::Spanned;
-use super::tokens::Token;
-use super::tree::{DynamicNode, SyntaxNode};
+use super::tree::SyntaxNode;
+use super::span;
 
 pub fn check<T>(src: &str, exp: T, found: T, cmp_spans: bool)
 where
-    T: Debug + PartialEq + SpanlessEq,
+    T: Debug + PartialEq,
 {
-    let cmp = if cmp_spans { PartialEq::eq } else { SpanlessEq::spanless_eq };
-    if !cmp(&exp, &found) {
+    span::set_cmp(cmp_spans);
+    let equal = exp == found;
+    span::set_cmp(true);
+
+    if !equal {
         println!("source:   {:?}", src);
         println!("expected: {:#?}", exp);
         println!("found:    {:#?}", found);
@@ -72,142 +71,3 @@ impl Layout for DebugNode {
         unimplemented!()
     }
 }
-
-/// Compares elements by only looking at values and ignoring spans.
-pub trait SpanlessEq<Rhs = Self> {
-    fn spanless_eq(&self, other: &Rhs) -> bool;
-}
-
-impl SpanlessEq for SyntaxNode {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        fn downcast<'a>(func: &'a (dyn DynamicNode + 'static)) -> &'a DebugNode {
-            func.downcast::<DebugNode>().expect("not a debug node")
-        }
-
-        match (self, other) {
-            (Self::Dyn(a), Self::Dyn(b)) => {
-                downcast(a.as_ref()).spanless_eq(downcast(b.as_ref()))
-            }
-            (Self::Par(a), Self::Par(b)) => a.spanless_eq(b),
-            (a, b) => a == b,
-        }
-    }
-}
-
-impl SpanlessEq for DebugNode {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.0.spanless_eq(&other.0)
-            && self.1.spanless_eq(&other.1)
-    }
-}
-
-impl SpanlessEq for FuncCall {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.name.spanless_eq(&other.name)
-            && self.args.spanless_eq(&other.args)
-    }
-}
-
-impl SpanlessEq for FuncArgs {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.key.spanless_eq(&other.key)
-            && self.pos.spanless_eq(&other.pos)
-    }
-}
-
-impl SpanlessEq for FuncArg {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        match (self, other) {
-            (FuncArg::Pos(a), FuncArg::Pos(b)) => a.spanless_eq(b),
-            (FuncArg::Key(a), FuncArg::Key(b)) => a.spanless_eq(b),
-            _ => false,
-        }
-    }
-}
-
-impl SpanlessEq for Expr {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        match (self, other) {
-            (Expr::Tuple(a), Expr::Tuple(b)) => a.spanless_eq(b),
-            (Expr::NamedTuple(a), Expr::NamedTuple(b)) => a.spanless_eq(b),
-            (Expr::Object(a), Expr::Object(b)) => a.spanless_eq(b),
-            (Expr::Neg(a), Expr::Neg(b)) => a.spanless_eq(&b),
-            (Expr::Add(a1, a2), Expr::Add(b1, b2)) => a1.spanless_eq(&b1) && a2.spanless_eq(&b2),
-            (Expr::Sub(a1, a2), Expr::Sub(b1, b2)) => a1.spanless_eq(&b1) && a2.spanless_eq(&b2),
-            (Expr::Mul(a1, a2), Expr::Mul(b1, b2)) => a1.spanless_eq(&b1) && a2.spanless_eq(&b2),
-            (Expr::Div(a1, a2), Expr::Div(b1, b2)) => a1.spanless_eq(&b1) && a2.spanless_eq(&b2),
-            (a, b) => a == b,
-        }
-    }
-}
-
-impl SpanlessEq for Tuple {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.0.spanless_eq(&other.0)
-    }
-}
-
-impl SpanlessEq for NamedTuple {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.name.v == other.name.v
-            && self.tuple.v.spanless_eq(&other.tuple.v)
-    }
-}
-
-impl SpanlessEq for Object {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.0.spanless_eq(&other.0)
-    }
-}
-
-impl SpanlessEq for Pair {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.key.spanless_eq(&other.key) && self.value.spanless_eq(&other.value)
-    }
-}
-
-impl<T: SpanlessEq> SpanlessEq for Vec<T> {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.len() == other.len()
-            && self.iter().zip(other).all(|(x, y)| x.spanless_eq(&y))
-    }
-}
-
-impl<T: SpanlessEq> SpanlessEq for Spanned<T> {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        self.v.spanless_eq(&other.v)
-    }
-}
-
-impl<T: SpanlessEq> SpanlessEq for Box<T> {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        (&**self).spanless_eq(&**other)
-    }
-}
-
-impl<T: SpanlessEq> SpanlessEq for Option<T> {
-    fn spanless_eq(&self, other: &Self) -> bool {
-        match (self, other) {
-            (Some(a), Some(b)) => a.spanless_eq(b),
-            (None, None) => true,
-            _ => false,
-        }
-    }
-}
-
-macro_rules! impl_through_partial_eq {
-    ($type:ty) => {
-        impl SpanlessEq for $type {
-            fn spanless_eq(&self, other: &$type) -> bool {
-                self == other
-            }
-        }
-    };
-}
-
-impl_through_partial_eq!(Token<'_>);
-impl_through_partial_eq!(Ident);
-
-// Implement for string and decoration to be able to compare feedback.
-impl_through_partial_eq!(String);
-impl_through_partial_eq!(Decoration);