Add desugar command and desugar programs

src/desugar/program.rs

@@ -0,0 +1,48 @@
+use crate::ast::{Expr, Lit, Program, Space, TableLit};
+use crate::span::HasSpan;
+
+impl Program {
+    pub fn desugar(self) -> (Self, bool) {
+        match self {
+            Self::Expr { s0, expr, s1, span } => {
+                let (expr, desugared) = (expr, false); // TODO Implement
+                (Self::Expr { s0, expr, s1, span }, desugared)
+            }
+
+            Self::Module {
+                s0,
+                s1,
+                elems,
+                s2,
+                span,
+            } => {
+                let (elems, desugared) = (elems, false); // TODO Implement
+                if desugared {
+                    let new = Self::Module {
+                        s0,
+                        s1,
+                        elems,
+                        s2,
+                        span,
+                    };
+                    (new, true)
+                } else {
+                    let elems_span = elems.span();
+                    let table = TableLit {
+                        s0: s1,
+                        elems,
+                        s1: Space::empty(elems_span.at_end()),
+                        span: elems_span,
+                    };
+                    let new = Self::Expr {
+                        s0,
+                        expr: Expr::Lit(Lit::Table(table)),
+                        s1: s2,
+                        span,
+                    };
+                    (new, true)
+                }
+            }
+        }
+    }
+}