Switch typing to use traits

1 files changed, 132 insertions, 0 deletions

diff --git a/src/ast/typed.rs b/src/ast/typed.rs
new file mode 100644
index 0000000..48ca740
--- /dev/null
+++ b/src/ast/typed.rs
@@ -0,0 +1,132 @@
+use super::Typed;
+use std::collections::BTreeSet;
+use std::fmt::Display;
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct FirstSet {
+    inner: BTreeSet<char>,
+}
+
+impl FirstSet {
+    pub fn new() -> Self {
+        Self {
+            inner: BTreeSet::new(),
+        }
+    }
+
+    pub fn of_str(s: &str) -> Self {
+        let mut inner = BTreeSet::new();
+        s.chars().next().map(|c| inner.insert(c));
+
+        Self { inner }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    pub fn union(mut self, mut other: Self) -> Self {
+        self.inner.append(&mut other.inner);
+        self
+    }
+
+    pub fn intersect(&self, other: &Self) -> Self {
+        Self {
+            inner: self.inner.intersection(&other.inner).copied().collect(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct FlastSet {
+    inner: BTreeSet<char>,
+}
+
+impl FlastSet {
+    pub fn new() -> Self {
+        Self {
+            inner: BTreeSet::new(),
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    pub fn union_first(mut self, mut other: FirstSet) -> Self {
+        self.inner.append(&mut other.inner);
+        self
+    }
+
+    pub fn union(mut self, mut other: Self) -> Self {
+        self.inner.append(&mut other.inner);
+        self
+    }
+
+    pub fn intersect_first(&self, other: &FirstSet) -> Self {
+        Self {
+            inner: self.inner.intersection(&other.inner).copied().collect(),
+        }
+    }
+
+    pub fn intersect(&self, other: &Self) -> Self {
+        Self {
+            inner: self.inner.intersection(&other.inner).copied().collect(),
+        }
+    }
+}
+
+pub trait NullContext {
+    type PushNull: NullContext;
+
+    fn get_nullable(&self, index: usize) -> Option<bool>;
+
+    fn push_nullable<F: FnOnce(&mut Self::PushNull) -> R, R>(&mut self, nullable: bool, f: F) -> R;
+}
+
+pub trait FirstSetContext: NullContext {
+    type PushFirstSet: FirstSetContext;
+
+    fn get_first_set(&self, index: usize) -> Option<FirstSet>;
+
+    fn push_first_set<F: FnOnce(&mut Self::PushFirstSet) -> R, R>(
+        &mut self,
+        nullable: bool,
+        first_set: FirstSet,
+        f: F,
+    ) -> R;
+}
+
+pub trait FlastSetContext: FirstSetContext {
+    type PushFlastSet: FlastSetContext;
+
+    fn get_flast_set(&self, index: usize) -> Option<FlastSet>;
+
+    fn push_flast_set<F: FnOnce(&mut Self::PushFlastSet) -> R, R>(
+        &mut self,
+        nullable: bool,
+        first_set: FirstSet,
+        flast_set: FlastSet,
+        f: F,
+    ) -> R;
+}
+
+pub trait Type {
+    type Err: Display;
+
+    /// # Errors
+    /// Returns [`None`] if the nullity cannot be determined.
+    fn is_nullable<C: NullContext>(&self, context: &mut C) -> Option<bool>;
+
+    /// # Errors
+    /// Returns [`None`] if the first set cannot be determined.
+    fn first_set<C: FirstSetContext>(&self, context: &mut C) -> Option<FirstSet>;
+
+    /// # Errors
+    /// Returns [`None`] if the flast set cannot be determined.
+    fn flast_set<C: FlastSetContext>(&self, context: &mut C) -> Option<FlastSet>;
+
+    /// # Errors
+    /// Returns an [`Err`] if this term is not well typed.
+    fn well_typed<C: FlastSetContext>(self, context: &mut C) -> Result<Typed, Self::Err>;
+}