diff --git a/compiler/erg_common/str.rs b/compiler/erg_common/str.rs
index cde076e5..d92f9074 100644
--- a/compiler/erg_common/str.rs
+++ b/compiler/erg_common/str.rs
@@ -139,4 +139,55 @@ impl Str {
             .map(|c| c.is_uppercase())
             .unwrap_or(false)
     }
+
+    pub fn split_with(&self, seps: &[&str]) -> Vec<&str> {
+        let mut ret = vec![];
+        let mut start = 0;
+        #[allow(unused_assignments)]
+        let mut end = 0;
+        let mut i = 0;
+        while i < self.len() {
+            let mut found = false;
+            for sep in seps {
+                if self[i..].starts_with(sep) {
+                    end = i;
+                    ret.push(&self[start..end]);
+                    start = i + sep.len();
+                    i = start;
+                    found = true;
+                    break;
+                }
+            }
+            if !found {
+                i += 1;
+            }
+        }
+        ret.push(&self[start..]);
+        ret
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_split_with() {
+        assert_eq!(
+            Str::ever("aa::bb.cc").split_with(&[".", "::"]),
+            vec!["aa", "bb", "cc"]
+        );
+        assert_eq!(
+            Str::ever("aa::bb.cc").split_with(&["::", "."]),
+            vec!["aa", "bb", "cc"]
+        );
+        assert_eq!(
+            Str::ever("aaxxbbyycc").split_with(&["xx", "yy"]),
+            vec!["aa", "bb", "cc"]
+        );
+        assert_ne!(
+            Str::ever("aaxxbbyycc").split_with(&["xx", "yy"]),
+            vec!["aa", "bb", "ff"]
+        );
+    }
 }
diff --git a/compiler/erg_compiler/context/inquire.rs b/compiler/erg_compiler/context/inquire.rs
index 7a78be17..95368b75 100644
--- a/compiler/erg_compiler/context/inquire.rs
+++ b/compiler/erg_compiler/context/inquire.rs
@@ -1547,9 +1547,15 @@ impl Context {
                 if let Some((_, ctx)) = self.rec_get_mono_type(&typ.local_name()) {
                     return Some(ctx);
                 }
-                let path = name.split("::").next().unwrap_or(name);
-                let path = path.split('.').next().unwrap_or(path);
-                let path = self.resolve_path(Path::new(path));
+                // e.g. http.client.Response -> http.client
+                let mut namespaces = name.split_with(&[".", "::"]);
+                let type_name = namespaces.pop().unwrap(); // Response
+                let path = Path::new(namespaces.remove(0));
+                let mut path = self.resolve_path(path);
+                for p in namespaces.into_iter() {
+                    path = self.push_path(path, Path::new(p));
+                }
+                log!("{}", path.display());
                 if let Some(ctx) = self
                     .mod_cache
                     .as_ref()
@@ -1560,7 +1566,7 @@ impl Context {
                             .and_then(|cache| cache.ref_ctx(path.as_path()))
                     })
                 {
-                    if let Some((_, ctx)) = ctx.rec_get_mono_type(&typ.local_name()) {
+                    if let Some((_, ctx)) = ctx.rec_get_mono_type(type_name) {
                         return Some(ctx);
                     }
                 }
@@ -1570,9 +1576,13 @@ impl Context {
                     return Some(ctx);
                 }
                 // NOTE: This needs to be changed if we want to be able to define classes/traits outside of the top level
-                let path = name.split("::").next().unwrap_or(name);
-                let path = path.split('.').next().unwrap_or(path);
-                let path = self.resolve_path(Path::new(path));
+                let mut namespaces = name.split_with(&[".", "::"]);
+                let type_name = namespaces.pop().unwrap(); // Response
+                let path = Path::new(namespaces.remove(0));
+                let mut path = self.resolve_path(path);
+                for p in namespaces.into_iter() {
+                    path = self.push_path(path, Path::new(p));
+                }
                 if let Some(ctx) = self
                     .mod_cache
                     .as_ref()
@@ -1583,7 +1593,7 @@ impl Context {
                             .and_then(|cache| cache.ref_ctx(path.as_path()))
                     })
                 {
-                    if let Some((_, ctx)) = ctx.rec_get_poly_type(&typ.local_name()) {
+                    if let Some((_, ctx)) = ctx.rec_get_poly_type(type_name) {
                         return Some(ctx);
                     }
                 }
@@ -1752,6 +1762,23 @@ impl Context {
         }
     }
 
+    pub(crate) fn push_path(&self, mut path: PathBuf, add: &Path) -> PathBuf {
+        path.pop(); // __init__.d.er
+        if let Ok(path) = path.join(add).canonicalize() {
+            path
+        } else if let Ok(path) = path.join(format!("{}.d.er", add.display())).canonicalize() {
+            path
+        } else if let Ok(path) = path
+            .join(format!("{}.d", add.display()))
+            .join("__init__.d.er")
+            .canonicalize()
+        {
+            path
+        } else {
+            todo!("{} {}", path.display(), add.display())
+        }
+    }
+
     // FIXME: 現在の実装だとimportしたモジュールはどこからでも見れる
     pub(crate) fn get_mod(&self, name: &str) -> Option<&Context> {
         let t = self.get_var_info(name).map(|(_, vi)| vi.t.clone()).ok()?;
diff --git a/compiler/erg_compiler/context/instantiate.rs b/compiler/erg_compiler/context/instantiate.rs
index 50c4dac9..5109fc42 100644
--- a/compiler/erg_compiler/context/instantiate.rs
+++ b/compiler/erg_compiler/context/instantiate.rs
@@ -824,7 +824,20 @@ impl Context {
         expr: &ast::ConstExpr,
     ) -> SingleTyCheckResult<Type> {
         match expr {
-            ast::ConstExpr::Accessor(ast::ConstAccessor::Local(name)) => Ok(mono(name.inspect())),
+            ast::ConstExpr::Accessor(ast::ConstAccessor::Local(name)) => {
+                if let Some((typ, _)) = self.rec_get_type(name.inspect()) {
+                    Ok(typ.clone())
+                } else {
+                    Err(TyCheckError::no_var_error(
+                        self.cfg.input.clone(),
+                        line!() as usize,
+                        name.loc(),
+                        self.caused_by(),
+                        name.inspect(),
+                        self.get_similar_name(name.inspect()),
+                    ))
+                }
+            }
             _ => todo!(),
         }
     }
diff --git a/compiler/erg_compiler/context/register.rs b/compiler/erg_compiler/context/register.rs
index 0fbd9e52..eeea6cfe 100644
--- a/compiler/erg_compiler/context/register.rs
+++ b/compiler/erg_compiler/context/register.rs
@@ -29,7 +29,6 @@ use crate::error::{
 };
 use crate::hir;
 use crate::hir::Literal;
-use crate::mod_cache::SharedModuleCache;
 use crate::varinfo::{Mutability, ParamIdx, VarInfo, VarKind};
 use Mutability::*;
 use RegistrationMode::*;
@@ -1016,30 +1015,16 @@ impl Context {
         mod_name: &Literal,
     ) -> CompileResult<PathBuf> {
         if kind.is_erg_import() {
-            self.import_erg_mod_using_cache(mod_name)
+            self.import_erg_mod(mod_name)
         } else {
             self.import_py_mod(mod_name)
         }
     }
 
-    fn import_erg_mod_using_cache(&mut self, mod_name: &Literal) -> CompileResult<PathBuf> {
+    fn import_erg_mod(&self, mod_name: &Literal) -> CompileResult<PathBuf> {
         let __name__ = enum_unwrap!(mod_name.value.clone(), ValueObj::Str);
         let mod_cache = self.mod_cache.as_ref().unwrap();
         let py_mod_cache = self.py_mod_cache.as_ref().unwrap();
-        #[allow(clippy::match_single_binding)]
-        match &__name__[..] {
-            // TODO: erg builtin modules
-            _ => self.import_erg_mod(__name__, mod_name, mod_cache, py_mod_cache),
-        }
-    }
-
-    fn import_erg_mod(
-        &self,
-        __name__: Str,
-        mod_name: &Literal,
-        mod_cache: &SharedModuleCache,
-        py_mod_cache: &SharedModuleCache,
-    ) -> CompileResult<PathBuf> {
         let path = match self.cfg.input.local_resolve(Path::new(&__name__[..])) {
             Ok(path) => path,
             Err(err) => {
@@ -1097,6 +1082,27 @@ impl Context {
         path == pystd_path
     }
 
+    /// e.g. http.d/client.d.er -> http.client
+    /// math.d.er -> math
+    fn mod_name(&self, path: &Path) -> Str {
+        let mut name = path
+            .file_name()
+            .unwrap()
+            .to_str()
+            .unwrap()
+            .trim_end_matches(".d.er")
+            .to_string();
+        for parent in path.components().rev().skip(1) {
+            let parent = parent.as_os_str().to_str().unwrap();
+            if parent.ends_with(".d") {
+                name = parent.trim_end_matches(".d").to_string() + "." + &name;
+            } else {
+                break;
+            }
+        }
+        Str::from(name)
+    }
+
     fn import_py_mod(&self, mod_name: &Literal) -> CompileResult<PathBuf> {
         let __name__ = enum_unwrap!(mod_name.value.clone(), ValueObj::Str);
         let mod_cache = self.mod_cache.as_ref().unwrap();
@@ -1137,8 +1143,12 @@ impl Context {
         }
         let cfg = ErgConfig::with_module_path(path.clone());
         let src = cfg.input.read();
-        let mut builder =
-            HIRBuilder::new_with_cache(cfg, __name__, mod_cache.clone(), py_mod_cache.clone());
+        let mut builder = HIRBuilder::new_with_cache(
+            cfg,
+            self.mod_name(&path),
+            mod_cache.clone(),
+            py_mod_cache.clone(),
+        );
         match builder.build(src, "declare") {
             Ok(hir) => {
                 let ctx = builder.pop_mod_ctx();
diff --git a/compiler/erg_compiler/context/tyvar.rs b/compiler/erg_compiler/context/tyvar.rs
index 8d6b3962..929364b3 100644
--- a/compiler/erg_compiler/context/tyvar.rs
+++ b/compiler/erg_compiler/context/tyvar.rs
@@ -795,8 +795,8 @@ impl Context {
                 for attr in record.attrs.iter_mut() {
                     match &mut attr.sig {
                         hir::Signature::Var(var) => {
-                            var.t =
-                                self.deref_tyvar(mem::take(&mut var.t), Covariant, var.loc())?;
+                            *var.ref_mut_t() =
+                                self.deref_tyvar(mem::take(var.ref_mut_t()), Covariant, var.loc())?;
                         }
                         hir::Signature::Subr(subr) => {
                             subr.t =
@@ -851,8 +851,8 @@ impl Context {
                 if !def.sig.ref_t().is_quantified() {
                     match &mut def.sig {
                         hir::Signature::Var(var) => {
-                            var.t =
-                                self.deref_tyvar(mem::take(&mut var.t), Covariant, var.loc())?;
+                            *var.ref_mut_t() =
+                                self.deref_tyvar(mem::take(var.ref_mut_t()), Covariant, var.loc())?;
                         }
                         hir::Signature::Subr(subr) => {
                             subr.t =
diff --git a/compiler/erg_compiler/hir.rs b/compiler/erg_compiler/hir.rs
index c9658c07..601d2f4d 100644
--- a/compiler/erg_compiler/hir.rs
+++ b/compiler/erg_compiler/hir.rs
@@ -548,8 +548,8 @@ impl Accessor {
     pub fn local_name(&self) -> Option<&str> {
         match self {
             Self::Ident(ident) => ident.qual_name.as_ref().map(|s| {
-                let name = s.split("::").last().unwrap_or(&s[..]);
-                name.split('.').last().unwrap_or(name)
+                let mut seps = s.split_with(&[".", "::"]);
+                seps.remove(seps.len() - 1)
             }),
             _ => None,
         }
@@ -1200,22 +1200,39 @@ impl Locational for Block {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct VarSignature {
     pub ident: Identifier,
-    pub t: Type,
 }
 
 impl NestedDisplay for VarSignature {
     fn fmt_nest(&self, f: &mut fmt::Formatter<'_>, _level: usize) -> fmt::Result {
-        write!(f, "{}(: {})", self.ident, self.t)
+        write!(f, "{}", self.ident)
     }
 }
 
 impl_display_from_nested!(VarSignature);
 impl_locational!(VarSignature, ident);
-impl_t!(VarSignature);
+
+impl HasType for VarSignature {
+    #[inline]
+    fn ref_t(&self) -> &Type {
+        self.ident.ref_t()
+    }
+    #[inline]
+    fn ref_mut_t(&mut self) -> &mut Type {
+        self.ident.ref_mut_t()
+    }
+    #[inline]
+    fn signature_t(&self) -> Option<&Type> {
+        self.ident.signature_t()
+    }
+    #[inline]
+    fn signature_mut_t(&mut self) -> Option<&mut Type> {
+        self.ident.signature_mut_t()
+    }
+}
 
 impl VarSignature {
-    pub const fn new(ident: Identifier, t: Type) -> Self {
-        Self { ident, t }
+    pub const fn new(ident: Identifier) -> Self {
+        Self { ident }
     }
 
     pub fn inspect(&self) -> &Str {
diff --git a/compiler/erg_compiler/lib/pystd/http.d/__init__.d.er b/compiler/erg_compiler/lib/pystd/http.d/__init__.d.er
index c49b8e62..5375fa93 100644
--- a/compiler/erg_compiler/lib/pystd/http.d/__init__.d.er
+++ b/compiler/erg_compiler/lib/pystd/http.d/__init__.d.er
@@ -1 +1 @@
-.client = pyimport "./client"
+.client = pyimport "client"
diff --git a/compiler/erg_compiler/lib/pystd/http.d/client.d.er b/compiler/erg_compiler/lib/pystd/http.d/client.d.er
index d19fcaf2..33642f33 100644
--- a/compiler/erg_compiler/lib/pystd/http.d/client.d.er
+++ b/compiler/erg_compiler/lib/pystd/http.d/client.d.er
@@ -1 +1,3 @@
 .HTTPResponse: ClassType
+.HTTPResponse <: FileLike
+.HTTPResponse <: FileLike!
diff --git a/compiler/erg_compiler/lib/pystd/urllib.d/__init__.d.er b/compiler/erg_compiler/lib/pystd/urllib.d/__init__.d.er
index 5ed7890b..127a9678 100644
--- a/compiler/erg_compiler/lib/pystd/urllib.d/__init__.d.er
+++ b/compiler/erg_compiler/lib/pystd/urllib.d/__init__.d.er
@@ -1,2 +1,2 @@
-.parse = pyimport "./parse"
-.request = pyimport "./request"
+.parse = pyimport "parse"
+.request = pyimport "request"
diff --git a/compiler/erg_compiler/link.rs b/compiler/erg_compiler/link.rs
index 4b7ced63..09067e14 100644
--- a/compiler/erg_compiler/link.rs
+++ b/compiler/erg_compiler/link.rs
@@ -13,7 +13,7 @@ use erg_parser::token::{Token, TokenKind};
 use crate::ty::free::fresh_varname;
 use crate::ty::typaram::TyParam;
 use crate::ty::value::ValueObj;
-use crate::ty::{HasType, Type};
+use crate::ty::HasType;
 
 use crate::hir::*;
 use crate::mod_cache::SharedModuleCache;
@@ -312,7 +312,7 @@ impl<'a> Linker<'a> {
             let tmp =
                 Identifier::private_with_line(Str::from(fresh_varname()), expr.ln_begin().unwrap());
             let mod_def = Expr::Def(Def::new(
-                Signature::Var(VarSignature::new(tmp.clone(), Type::Uninited)),
+                Signature::Var(VarSignature::new(tmp.clone())),
                 DefBody::new(Token::dummy(), block, DefId(0)),
             ));
             let module = Expr::Accessor(Accessor::Ident(tmp));
diff --git a/compiler/erg_compiler/lower.rs b/compiler/erg_compiler/lower.rs
index 5b7c1787..0e3b3c1f 100644
--- a/compiler/erg_compiler/lower.rs
+++ b/compiler/erg_compiler/lower.rs
@@ -932,8 +932,9 @@ impl ASTLowerer {
                     body.id,
                     None,
                 )?;
-                let ident = hir::Identifier::bare(ident.dot.clone(), ident.name.clone());
-                let sig = hir::VarSignature::new(ident, found_body_t.clone());
+                let mut ident = hir::Identifier::bare(ident.dot.clone(), ident.name.clone());
+                ident.vi.t = found_body_t.clone();
+                let sig = hir::VarSignature::new(ident);
                 let body = hir::DefBody::new(body.op, block, body.id);
                 Ok(hir::Def::new(hir::Signature::Var(sig), body))
             }
@@ -1515,8 +1516,9 @@ impl ASTLowerer {
         };
         let id = body.id;
         self.ctx.assign_var_sig(&sig, found_body_t, id, py_name)?;
-        let ident = hir::Identifier::bare(ident.dot.clone(), ident.name.clone());
-        let sig = hir::VarSignature::new(ident, found_body_t.clone());
+        let mut ident = hir::Identifier::bare(ident.dot.clone(), ident.name.clone());
+        ident.vi.t = found_body_t.clone();
+        let sig = hir::VarSignature::new(ident);
         let body = hir::DefBody::new(body.op, block, body.id);
         Ok(hir::Def::new(hir::Signature::Var(sig), body))
     }
diff --git a/compiler/erg_compiler/ty/mod.rs b/compiler/erg_compiler/ty/mod.rs
index a83ea720..8256b6d5 100644
--- a/compiler/erg_compiler/ty/mod.rs
+++ b/compiler/erg_compiler/ty/mod.rs
@@ -1955,9 +1955,8 @@ impl Type {
     pub fn local_name(&self) -> Str {
         match self {
             Self::Mono(name) | Self::Poly { name, .. } => {
-                let name = name.split("::").last().unwrap_or(name);
-                let name = name.split('.').last().unwrap_or(name);
-                Str::rc(name)
+                let namespaces = name.split_with(&[".", "::"]);
+                Str::rc(namespaces.last().unwrap())
             }
             _ => self.qual_name(),
         }