Add Expr::GetAttr to IR, and change Lhs::Name to hold a NameId instead of a Sym

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

src/compile/ir.rs

@@ -10,12 +10,16 @@ pub enum Stmt {
 
 #[derive(Debug, Clone)]
 pub enum Lhs {
-    Name(Sym),
+    Name(NameId),
     Complex(Expr),
 }
 
 #[derive(Debug, Clone)]
 pub enum Expr {
+    GetAttr {
+        expr: Box<Expr>,
+        sym: Sym,
+    },
     Call(Box<Expr>, Vec<Expr>),
     Block(Vec<Stmt>),
     Num(i64),