Add "module" program variant

src/ast/program.rs

@@ -1,17 +1,32 @@
 use crate::span::{HasSpan, Span};
 
-use super::{Space, TableLitElem};
+use super::{Expr, Space, TableLitElem};
 
 #[derive(Debug, Clone)]
-pub struct Program {
-    pub elems: Vec<(Space, TableLitElem, Space)>,
-    /// `Some` if there is a trailing comma, `None` otherwise.
-    pub trailing_comma: Option<Space>,
-    pub span: Span,
+pub enum Program {
+    /// Structure: `s0 lit s1`
+    Expr {
+        s0: Space,
+        expr: Expr,
+        s1: Space,
+        span: Span,
+    },
+
+    /// Structure: `s0 module elems trailing_comma`
+    Module {
+        s0: Space,
+        elems: Vec<(Space, TableLitElem, Space)>,
+        /// `Some` if there is a trailing comma, `None` otherwise.
+        trailing_comma: Option<Space>,
+        span: Span,
+    },
 }
 
 impl HasSpan for Program {
     fn span(&self) -> Span {
-        self.span
+        match self {
+            Program::Expr { span, .. } => *span,
+            Program::Module { span, .. } => *span,
+        }
     }
 }