Add parser and AST, remove some stuff from lexer

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/syn/ast.rs

@@ -0,0 +1,52 @@
+use crate::syn::{op::*, span::*};
+
+pub enum Expr {
+    Base(BaseExpr),
+    Bin(Box<BinExpr>),
+    Un(Box<UnExpr>),
+}
+
+impl From<UnExpr> for Expr {
+    fn from(un: UnExpr) -> Self {
+        Expr::Un(Box::new(un))
+    }
+}
+
+impl From<BinExpr> for Expr {
+    fn from(bin: BinExpr) -> Self {
+        Expr::Bin(Box::new(bin))
+    }
+}
+
+impl From<BaseExpr> for Expr {
+    fn from(base: BaseExpr) -> Self {
+        Expr::Base(base)
+    }
+}
+
+pub struct BinExpr {
+    pub lhs: Expr,
+    pub op: BinOp,
+    pub rhs: Expr,
+}
+
+pub struct UnExpr {
+    pub op: UnOp,
+    pub expr: Expr,
+    pub span: Span,
+}
+
+pub enum BaseExprKind {
+    Ident,
+    Num,
+    Str,
+    Sym,
+    List(Vec<Expr>),
+    Object(Vec<(Expr, Expr)>),
+    Tuple(Vec<Expr>),
+}
+
+pub struct BaseExpr {
+    pub kind: BaseExprKind,
+    pub span: Span,
+}