graphcal-compiler 0.0.1-alpha.14

Type-safe, unit-aware, Git-friendly reactive programming language for engineering calculations
Documentation 
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/// Byte-offset span in source code. Compatible with `miette::SourceSpan`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Span {
    offset: usize,
    len: usize,
}

impl Span {
    #[must_use]
    pub const fn new(offset: usize, len: usize) -> Self {
        Self { offset, len }
    }

    /// Returns the byte offset.
    #[must_use]
    pub const fn offset(self) -> usize {
        self.offset
    }

    /// Returns the byte length.
    #[must_use]
    pub const fn len(self) -> usize {
        self.len
    }

    /// Returns `true` if the span has zero length.
    #[must_use]
    pub const fn is_empty(self) -> bool {
        self.len == 0
    }

    /// Merge two spans into one that covers both.
    #[must_use]
    pub fn merge(self, other: Self) -> Self {
        let start = self.offset.min(other.offset);
        let end = (self.offset + self.len).max(other.offset + other.len);
        Self::new(start, end - start)
    }
}

impl From<Span> for miette::SourceSpan {
    fn from(s: Span) -> Self {
        (s.offset, s.len).into()
    }
}

/// A value paired with its source span.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Spanned<T> {
    pub value: T,
    pub span: Span,
}

impl<T> Spanned<T> {
    /// Create a new spanned value.
    pub const fn new(value: T, span: Span) -> Self {
        Self { value, span }
    }
}

impl<T> std::ops::Deref for Spanned<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.value
    }
}

impl<T: std::fmt::Display> std::fmt::Display for Spanned<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.value.fmt(f)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn span_merge() {
        let a = Span::new(0, 5);
        let b = Span::new(10, 3);
        let merged = a.merge(b);
        assert_eq!(merged.offset(), 0);
        assert_eq!(merged.len(), 13);
    }

    #[test]
    fn span_merge_overlapping() {
        let a = Span::new(2, 5);
        let b = Span::new(4, 6);
        let merged = a.merge(b);
        assert_eq!(merged.offset(), 2);
        assert_eq!(merged.len(), 8);
    }

    #[test]
    fn span_to_miette() {
        let s = Span::new(10, 5);
        let ms: miette::SourceSpan = s.into();
        assert_eq!(ms.offset(), 10);
        assert_eq!(ms.len(), 5);
    }

    #[test]
    fn spanned_eq_considers_span() {
        use crate::syntax::names::DeclName;

        let a = Spanned::new(DeclName::new("x"), Span::new(0, 1));
        let b = Spanned::new(DeclName::new("x"), Span::new(10, 11));
        assert_ne!(a, b);
    }

    #[test]
    fn spanned_ne_different_value() {
        use crate::syntax::names::DeclName;

        let a = Spanned::new(DeclName::new("x"), Span::new(0, 1));
        let b = Spanned::new(DeclName::new("y"), Span::new(0, 1));
        assert_ne!(a, b);
    }

    #[test]
    fn spanned_hash_considers_span() {
        use crate::syntax::names::DeclName;
        use std::hash::{DefaultHasher, Hash, Hasher};

        let a = Spanned::new(DeclName::new("x"), Span::new(0, 1));
        let b = Spanned::new(DeclName::new("x"), Span::new(10, 11));
        let mut ha = DefaultHasher::new();
        a.hash(&mut ha);
        let mut hb = DefaultHasher::new();
        b.hash(&mut hb);
        assert_ne!(ha.finish(), hb.finish());
    }
}