Base compilation of some kind of file to a list of instructions seems to work(!)

I'm able to compile some basic expressions into instructions using the
`not` binary. Big first step, now we need to introduce branches and
loops to the syntax.

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

src/compile/thunk.rs

@@ -234,7 +234,7 @@ impl Visit for CompileBody<'_> {
         self.compile.collect_locals(body);
         let mut thunk = Thunk::Nop;
 
-        for stmt in body.body.iter() {
+        for stmt in body.iter() {
             thunk.push_thunk(stmt.accept(self)?);
         }
 
@@ -347,7 +347,13 @@ impl Visit for CompileBody<'_> {
         let thunk = match atom {
             Atom::Ident(ident) => {
                 let sym = global_sym(ident.to_string());
-                let local = self.compile.lookup_scope(sym).unwrap();
+                let local = if let Some(local) = self.compile.lookup_scope(sym) {
+                    local
+                } else {
+                    // create a global that gets looked up instead, since nothing with this name
+                    // has been declared/assigned in this scope
+                    self.compile.create_global(sym)
+                };
                 // get local
                 Inst::PushLocal(local).into()
             }