fallible iterator

src/ast/main.rs

@@ -31,17 +31,18 @@ fn parse_num_or_id() {
 type Error = String;
 
 fn type_check(stmts: &Stmts) -> Result<(), Error> {
-    for i in stmts {
-        match i {
+    let r: Result<(), Error> = stmts.iter().try_for_each(|i| match i {
         Stmt::Let(_, _) => {
             println!("let");
+            Ok(())
         }
         Stmt::If(_, _, __) => {
             println!("if");
+            Err("error in if".to_string())?
         }
-        }
-    }
-    Ok(())
+    });
+    println!("here we can do something before returning");
+    r
 }
 
 #[test]
@@ -49,6 +50,7 @@ fn test_stmts() {
     let stmts = vec![
         Stmt::Let("a".to_string(), NumOrId::Num(1)),
         Stmt::Let("b".to_string(), NumOrId::Num(2)),
+        Stmt::If("b".to_string(), Stmts::new(), None),
         Stmt::Let("c".to_string(), NumOrId::Num(3)),
     ];
     type_check(&stmts).unwrap();