Pretty print expressions partially

src/pretty.rs

@@ -1,2 +1,3 @@
 mod basic;
+mod expr;
 mod program;

src/pretty/expr.rs

@@ -0,0 +1,48 @@
+use pretty::RcDoc;
+
+use crate::ast::Expr;
+
+impl Expr {
+    pub fn to_doc(&self) -> RcDoc {
+        match self {
+            Expr::Lit(lit) => RcDoc::text("<lit>"),
+            Expr::Call(call) => RcDoc::text("<call>"),
+            Expr::Field(field) => RcDoc::text("<field>"),
+            Expr::Var(var) => RcDoc::text("<var>"),
+            Expr::TableConstr(constr) => RcDoc::text("<onstr>"),
+            Expr::TableDestr(destr) => RcDoc::text("<destr>"),
+            Expr::FuncDef(def) => RcDoc::text("<def>"),
+            Expr::Paren {
+                s0,
+                inner,
+                s1,
+                span: _,
+            } => RcDoc::text("(").append(inner.to_doc()).append(")"),
+
+            // TODO Check whether parentheses are necessary
+            Expr::Neg {
+                minus: _,
+                s0,
+                expr,
+                span: _,
+            } => RcDoc::text("-").append(expr.to_doc()),
+
+            // TODO Check whether parentheses are necessary
+            Expr::Not {
+                not: _,
+                s0,
+                expr,
+                span: _,
+            } => RcDoc::text("not ").append(expr.to_doc()),
+
+            Expr::BinOp {
+                left,
+                s0,
+                op,
+                s1,
+                right,
+                span: _,
+            } => RcDoc::text("<binop>"),
+        }
+    }
+}

src/pretty/program.rs

@@ -10,7 +10,7 @@ impl Program {
                 expr,
                 s1,
                 span: _,
-            } => RcDoc::text("<expr>"),
+            } => expr.to_doc(),
             Program::Module {
                 s0,
                 s1,