diff --git a/Cargo.lock b/Cargo.lock
index 6fe2910..7f145f2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -150,9 +150,9 @@ checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
 
 [[package]]
 name = "els"
-version = "0.1.62"
+version = "0.1.63-nightly.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98d4bb4cbce0f519100ba0d6aa5541aa69aa00b0f61bdb862c81124f9cf38cea"
+checksum = "99d2ae54e13d256ec9a09554249ccc498c31022836c76bc5dc1b11b072f0a753"
 dependencies = [
  "erg_common",
  "erg_compiler",
@@ -166,9 +166,9 @@ dependencies = [
 
 [[package]]
 name = "erg_common"
-version = "0.6.50"
+version = "0.6.51-nightly.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "15fcd8b1d8d47238d1488f7a05a8131b77b89adb54c867327b83db272a919344"
+checksum = "abc654d256215d0d1b2ccb5d1e80c9188148dd59714d0a642f5738bf0271197a"
 dependencies = [
  "backtrace-on-stack-overflow",
  "erg_proc_macros",
@@ -179,9 +179,9 @@ dependencies = [
 
 [[package]]
 name = "erg_compiler"
-version = "0.6.50"
+version = "0.6.51-nightly.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4a5b708d63c430435aac418e0822ef435b6b26c5338e5795130cce308f319505"
+checksum = "223b817462901cfef987f38c21a18f9637f7f796dbe58a3b51a1e09489fd25be"
 dependencies = [
  "erg_common",
  "erg_parser",
@@ -189,9 +189,9 @@ dependencies = [
 
 [[package]]
 name = "erg_parser"
-version = "0.6.50"
+version = "0.6.51-nightly.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6b79c7b5789c93deeeb21cbe9d4e0c62db60712a187a1c260210079d3750b4be"
+checksum = "13d9eaf0b3076b05cb7290be98de5c1cbd73ab7a72b090f67d5911e03d062501"
 dependencies = [
  "erg_common",
  "erg_proc_macros",
@@ -200,9 +200,9 @@ dependencies = [
 
 [[package]]
 name = "erg_proc_macros"
-version = "0.6.50"
+version = "0.6.51-nightly.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "99659bb992c4e9da4af751d63fa126034025ffe79e07bfdbf013d9e165e768fc"
+checksum = "e3d2e883cddea276b76add108da8d16276d9d6962a0079561515e701121a3e1a"
 dependencies = [
  "quote",
  "syn 1.0.109",
diff --git a/Cargo.toml b/Cargo.toml
index d2a9d99..2212590 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,9 +24,9 @@ edition = "2021"
 repository = "https://github.com/mtshiba/pylyzer"
 
 [workspace.dependencies]
-erg_common = { version = "0.6.50", features = ["py_compat", "els"] }
-erg_compiler = { version = "0.6.50", features = ["py_compat", "els"] }
-els = { version = "0.1.50", features = ["py_compat"] }
+erg_common = { version = "0.6.51-nightly.0", features = ["py_compat", "els"] }
+erg_compiler = { version = "0.6.51-nightly.0", features = ["py_compat", "els"] }
+els = { version = "0.1.63-nightly.0", features = ["py_compat"] }
 # rustpython-parser = { version = "0.3.0", features = ["all-nodes-with-ranges", "location"] }
 # rustpython-ast = { version = "0.3.0", features = ["all-nodes-with-ranges", "location"] }
 rustpython-parser = { git = "https://github.com/RustPython/Parser", version = "0.4.0", features = ["all-nodes-with-ranges", "location"] }
diff --git a/crates/py2erg/convert.rs b/crates/py2erg/convert.rs
index 6f61d9c..b478f2f 100644
--- a/crates/py2erg/convert.rs
+++ b/crates/py2erg/convert.rs
@@ -320,6 +320,19 @@ pub struct BlockInfo {
     pub kind: BlockKind,
 }
 
+#[derive(Debug)]
+pub enum ReturnKind {
+    None,
+    Return,
+    Yield,
+}
+
+impl ReturnKind {
+    pub const fn is_none(&self) -> bool {
+        matches!(self, Self::None)
+    }
+}
+
 #[derive(Debug)]
 pub struct LocalContext {
     pub name: String,
@@ -329,6 +342,7 @@ pub struct LocalContext {
     type_vars: HashMap<String, TypeVarInfo>,
     // e.g. def id(x: T) -> T: ... => appeared_types = {T}
     appeared_type_names: HashSet<String>,
+    return_kind: ReturnKind,
 }
 
 impl LocalContext {
@@ -339,6 +353,7 @@ impl LocalContext {
             names: HashMap::new(),
             type_vars: HashMap::new(),
             appeared_type_names: HashSet::new(),
+            return_kind: ReturnKind::None,
         }
     }
 }
@@ -667,6 +682,14 @@ impl ASTConverter {
         &self.contexts.last().unwrap().name
     }
 
+    fn cur_context(&self) -> &LocalContext {
+        self.contexts.last().unwrap()
+    }
+
+    fn cur_context_mut(&mut self) -> &mut LocalContext {
+        self.contexts.last_mut().unwrap()
+    }
+
     fn parent_name(&self) -> &str {
         &self.contexts[self.contexts.len().saturating_sub(2)].name
     }
@@ -2033,6 +2056,11 @@ impl ASTConverter {
                 );
                 Expr::Compound(Compound::new(vec![Expr::Def(def), target]))
             }
+            py_ast::Expr::Yield(_) => {
+                self.cur_context_mut().return_kind = ReturnKind::Yield;
+                log!(err "unimplemented: {:?}", expr);
+                Expr::Dummy(Dummy::new(None, vec![]))
+            }
             _other => {
                 log!(err "unimplemented: {:?}", _other);
                 Expr::Dummy(Dummy::new(None, vec![]))
@@ -2087,7 +2115,7 @@ impl ASTConverter {
     //     self.y = y
     //     self.z = z
     // ↓
-    // requirement : {x: Int, y: Int, z: Never}
+    // requirement : {x: Int, y: Int, z: Any}
     // returns     : .__call__(x: Int, y: Int, z: Obj): Self = .unreachable()
     fn extract_init(&mut self, base_type: &mut Option<Expr>, init_def: Def) -> Option<Def> {
         self.check_init_sig(&init_def.sig)?;
@@ -2134,9 +2162,8 @@ impl ASTConverter {
                         } else if let Some(typ) = redef.t_spec.map(|t_spec| t_spec.t_spec_as_expr) {
                             *typ
                         } else {
-                            Expr::from(Accessor::Ident(Identifier::public_with_line(
-                                DOT,
-                                "Never".into(),
+                            Expr::from(Accessor::Ident(Identifier::private_with_line(
+                                "Any".into(),
                                 attr.obj.ln_begin().unwrap_or(0),
                             )))
                         };
@@ -2473,8 +2500,22 @@ impl ASTConverter {
                     .unwrap_or(func_def.type_params)
             };
             let bounds = self.get_type_bounds(type_params);
-            let sig = Signature::Subr(SubrSignature::new(decos, ident, bounds, params, return_t));
+            let mut sig =
+                Signature::Subr(SubrSignature::new(decos, ident, bounds, params, return_t));
             let block = self.convert_block(func_def.body, BlockKind::Function);
+            if self.cur_context().return_kind.is_none() {
+                let Signature::Subr(subr) = &mut sig else {
+                    unreachable!()
+                };
+                if subr.return_t_spec.is_none() {
+                    let none = TypeSpecWithOp::new(
+                        Token::dummy(TokenKind::Colon, ":"),
+                        TypeSpec::mono(Identifier::private("NoneType".into())),
+                        Expr::static_local("NoneType"),
+                    );
+                    subr.return_t_spec = Some(Box::new(none));
+                }
+            }
             let body = DefBody::new(EQUAL, block, DefId(0));
             let def = Def::new(sig, body);
             self.pop();
@@ -3030,6 +3071,7 @@ impl ASTConverter {
                 }
             }
             py_ast::Stmt::Return(return_) => {
+                self.cur_context_mut().return_kind = ReturnKind::Return;
                 let loc = return_.location();
                 let value = return_
                     .value
diff --git a/crates/pylyzer_core/handle_err.rs b/crates/pylyzer_core/handle_err.rs
index 840efa6..e6a0879 100644
--- a/crates/pylyzer_core/handle_err.rs
+++ b/crates/pylyzer_core/handle_err.rs
@@ -37,10 +37,11 @@ fn handle_name_error(error: CompileError) -> Option<CompileError> {
         || {
             main.contains(" is not defined") && {
                 let name = StyledStr::destyle(main.trim_end_matches(" is not defined"));
-                error
-                    .core
-                    .get_hint()
-                    .is_some_and(|hint| hint.contains(name))
+                name == "Any"
+                    || error
+                        .core
+                        .get_hint()
+                        .is_some_and(|hint| hint.contains(name))
             }
         }
     {
diff --git a/tests/class.py b/tests/class.py
index 24edc40..452359b 100644
--- a/tests/class.py
+++ b/tests/class.py
@@ -98,3 +98,10 @@ class MyList(list):
             return MyList(lis)
         else:
             return None
+
+class Implicit:
+    def __init__(self):
+        self.foo = False
+
+    def set_foo(self):
+        self.foo = True
diff --git a/tests/err/class.py b/tests/err/class.py
new file mode 100644
index 0000000..ee6dfd7
--- /dev/null
+++ b/tests/err/class.py
@@ -0,0 +1,4 @@
+class Foo:
+    def invalid_append(self):
+        paths: list[str] = []
+        paths.append(self)  # ERR
diff --git a/tests/projection.py b/tests/projection.py
index 925c8ab..0eec72a 100644
--- a/tests/projection.py
+++ b/tests/projection.py
@@ -1,5 +1,5 @@
 def imaginary(x):
-    x.imag
+    return x.imag
 
 assert imaginary(1) == 0
 assert imaginary(1.0) <= 0.0
@@ -8,7 +8,7 @@ print(imaginary("a")) # ERR
 class C:
     def method(self, x): return x
 def call_method(obj, x):
-    obj.method(x)
+    return obj.method(x)
 
 c = C()
 assert call_method(c, 1) == 1
diff --git a/tests/test.rs b/tests/test.rs
index 8f7ade9..9a78079 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -103,6 +103,11 @@ fn exec_class() -> Result<(), String> {
     expect("tests/class.py", 0, 6)
 }
 
+#[test]
+fn exec_class_err() -> Result<(), String> {
+    expect("tests/err/class.py", 0, 1)
+}
+
 #[test]
 fn exec_errors() -> Result<(), String> {
     expect("tests/errors.py", 0, 3)