Fix #272

compiler/erg_common/dict.rs

@@ -127,6 +127,14 @@ impl<K, V> Dict<K, V> {
     pub fn clear(&mut self) {
         self.dict.clear();
     }
+
+    /// remove all elements for which the predicate returns false
+    pub fn retain<F>(&mut self, f: F)
+    where
+        F: FnMut(&K, &mut V) -> bool,
+    {
+        self.dict.retain(f);
+    }
 }
 
 impl<K, V> IntoIterator for Dict<K, V> {

compiler/erg_compiler/context/mod.rs

@@ -950,6 +950,12 @@ impl Context {
         self.kind = kind;
     }
 
+    pub(crate) fn clear_invalid_vars(&mut self) {
+        self.locals.retain(|_, v| v.t != Failure);
+        self.decls.retain(|_, v| v.t != Failure);
+        self.params.retain(|(_, v)| v.t != Failure);
+    }
+
     pub fn pop(&mut self) -> Context {
         if let Some(parent) = self.outer.as_mut() {
             let parent = mem::take(parent);

compiler/erg_compiler/lower.rs

@@ -1978,6 +1978,7 @@ impl ASTLowerer {
                 }
             }
         }
+        self.ctx.clear_invalid_vars();
         self.ctx.check_decls().unwrap_or_else(|mut errs| {
             self.errs.append(&mut errs);
         });