Wire functions through everything, with some unimplemented, and add a basic scoped map.

src/syntax/ast.rs

@@ -16,7 +16,18 @@ use crate::syntax::Location;
 /// `validate` and it comes back without errors.
 #[derive(Clone, Debug, PartialEq)]
 pub struct Program {
-    pub statements: Vec<Statement>,
+    pub items: Vec<TopLevel>,
+}
+
+/// A thing that can sit at the top level of a file.
+///
+/// For the moment, these are statements and functions. Other things
+/// will likely be added in the future, but for now: just statements
+/// and functions
+#[derive(Clone, Debug, PartialEq)]
+pub enum TopLevel {
+    Statement(Statement),
+    Function(Name, Vec<Name>, Expression),
 }
 
 /// A Name.