1 files changed, 166 insertions, 0 deletions
diff --git a/src/ast/mod.rs b/src/ast/mod.rs
new file mode 100644
index 000000000000..2dcf955fe67c
--- /dev/null
+++ b/src/ast/mod.rs
@@ -0,0 +1,166 @@
+use std::borrow::Cow;
+use std::convert::TryFrom;
+use std::fmt::{self, Display, Formatter};
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct InvalidIdentifier<'a>(Cow<'a, str>);
+
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub struct Ident<'a>(pub Cow<'a, str>);
+
+impl<'a> From<&'a Ident<'a>> for &'a str {
+    fn from(id: &'a Ident<'a>) -> Self {
+        id.0.as_ref()
+    }
+}
+
+impl<'a> Display for Ident<'a> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+impl<'a> Ident<'a> {
+    pub fn to_owned(&self) -> Ident<'static> {
+        Ident(Cow::Owned(self.0.clone().into_owned()))
+    }
+
+    pub fn from_str_unchecked(s: &'a str) -> Self {
+        debug_assert!(is_valid_identifier(s));
+        Self(Cow::Borrowed(s))
+    }
+
+    pub fn from_string_unchecked(s: String) -> Self {
+        debug_assert!(is_valid_identifier(&s));
+        Self(Cow::Owned(s))
+    }
+}
+
+pub fn is_valid_identifier<S>(s: &S) -> bool
+where
+    S: AsRef<str> + ?Sized,
+{
+    s.as_ref()
+        .chars()
+        .any(|c| !c.is_alphanumeric() || !"_".contains(c))
+}
+
+impl<'a> TryFrom<&'a str> for Ident<'a> {
+    type Error = InvalidIdentifier<'a>;
+
+    fn try_from(s: &'a str) -> Result<Self, Self::Error> {
+        if is_valid_identifier(s) {
+            Ok(Ident(Cow::Borrowed(s)))
+        } else {
+            Err(InvalidIdentifier(Cow::Borrowed(s)))
+        }
+    }
+}
+
+impl<'a> TryFrom<String> for Ident<'a> {
+    type Error = InvalidIdentifier<'static>;
+
+    fn try_from(s: String) -> Result<Self, Self::Error> {
+        if is_valid_identifier(&s) {
+            Ok(Ident(Cow::Owned(s)))
+        } else {
+            Err(InvalidIdentifier(Cow::Owned(s)))
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum BinaryOperator {
+    /// `+`
+    Add,
+
+    /// `-`
+    Sub,
+
+    /// `*`
+    Mul,
+
+    /// `/`
+    Div,
+
+    /// `^`
+    Pow,
+
+    /// `==`
+    Equ,
+
+    /// `!=`
+    Neq,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum UnaryOperator {
+    /// !
+    Not,
+
+    /// -
+    Neg,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum Literal {
+    Int(u64),
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum Expr<'a> {
+    Ident(Ident<'a>),
+
+    Literal(Literal),
+
+    UnaryOp {
+        op: UnaryOperator,
+        rhs: Box<Expr<'a>>,
+    },
+
+    BinaryOp {
+        lhs: Box<Expr<'a>>,
+        op: BinaryOperator,
+        rhs: Box<Expr<'a>>,
+    },
+
+    Let {
+        bindings: Vec<(Ident<'a>, Expr<'a>)>,
+        body: Box<Expr<'a>>,
+    },
+
+    If {
+        condition: Box<Expr<'a>>,
+        then: Box<Expr<'a>>,
+        else_: Box<Expr<'a>>,
+    },
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct Fun<'a> {
+    pub name: Ident<'a>,
+    pub args: Vec<Ident<'a>>,
+    pub body: Expr<'a>,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum Decl<'a> {
+    Fun(Fun<'a>),
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+pub enum Type {
+    Int,
+    Float,
+    Bool,
+}
+
+impl Display for Type {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Int => f.write_str("int"),
+            Self::Float => f.write_str("float"),
+            Self::Bool => f.write_str("bool"),
+        }
+    }
+}