iter 22b.2.1: add Constraint struct, Type::Forall.constraints

crates/ailang-surface/src/parse.rs

@@ -858,6 +858,7 @@ impl<'a> Parser<'a> {
         self.expect_rparen("forall-type")?;
         Ok(Type::Forall {
             vars,
+            constraints: vec![],
             body: Box::new(body),
         })
     }

crates/ailang-surface/src/print.rs

@@ -296,7 +296,7 @@ fn write_type(out: &mut String, t: &Type) {
             }
             out.push(')');
         }
-        Type::Forall { vars, body } => {
+        Type::Forall { vars, constraints: _, body } => {
             out.push_str("(forall (vars");
             for v in vars {
                 out.push(' ');