diff --git a/buffer/buffer.mbt b/buffer/buffer.mbt
index 43f5d8fe9..b47d27cba 100644
--- a/buffer/buffer.mbt
+++ b/buffer/buffer.mbt
@@ -28,7 +28,7 @@
 /// buf.write_char("t")
 /// println(buf.to_string()) // output: Test
 /// ```
-struct Buffer {
+struct T {
   mut bytes : Bytes
   mut len : Int
   initial_bytes : Bytes
@@ -36,7 +36,7 @@ struct Buffer {
 
 ///|
 /// Expand the buffer size if capacity smaller than required space.
-fn grow_if_necessary(self : Buffer, required : Int) -> Unit {
+fn grow_if_necessary(self : T, required : Int) -> Unit {
   // TODO: get rid of mut
   let mut enough_space = self.bytes.length()
   if enough_space <= 0 {
@@ -53,13 +53,13 @@ fn grow_if_necessary(self : Buffer, required : Int) -> Unit {
 
 ///|
 /// Return the given buffer's length in bytes.
-pub fn length(self : Buffer) -> Int {
+pub fn length(self : T) -> Int {
   self.len
 }
 
 ///|
 /// Return whether the given buffer is empty.
-pub fn is_empty(self : Buffer) -> Bool {
+pub fn is_empty(self : T) -> Bool {
   self.len == 0
 }
 
@@ -67,7 +67,7 @@ pub fn is_empty(self : Buffer) -> Bool {
 /// Return a new string contains the data in buffer.
 /// 
 /// @alert deprecated "Use `Buffer::to_unchecked_string` instead"
-pub fn to_string(self : Buffer) -> String {
+pub fn to_string(self : T) -> String {
   self.bytes.to_unchecked_string(offset=0, length=self.len)
 }
 
@@ -75,13 +75,13 @@ pub fn to_string(self : Buffer) -> String {
 /// Return a new unchecked string contains the data in buffer.
 /// Note this function does not validate the encoding of the byte sequence, 
 /// it simply copy the bytes into a new String.
-pub fn to_unchecked_string(self : Buffer) -> String {
+pub fn to_unchecked_string(self : T) -> String {
   self.bytes.to_unchecked_string(offset=0, length=self.len)
 }
 
 ///|
 /// Create a buffer with initial capacity (in bytes).
-pub fn Buffer::new(~size_hint : Int = 0) -> Buffer {
+pub fn T::new(~size_hint : Int = 0) -> T {
   let initial = if size_hint < 1 { 1 } else { size_hint }
   let bytes = Bytes::new(initial)
   { bytes, len: 0, initial_bytes: bytes }
@@ -89,19 +89,19 @@ pub fn Buffer::new(~size_hint : Int = 0) -> Buffer {
 
 ///|
 /// Write a string into buffer.
-pub fn write_string(self : Buffer, value : String) -> Unit {
+pub fn write_string(self : T, value : String) -> Unit {
   self.grow_if_necessary(self.len + value.length() * 2)
   self.bytes.blit_from_string(self.len, value, 0, value.length())
   self.len += value.length() * 2
 }
 
 ///|
-pub fn write_object(self : Buffer, value : Show) -> Unit {
+pub fn write_object(self : T, value : Show) -> Unit {
   self.write_string(value.to_string())
 }
 
 ///|
-pub fn write_bytes(self : Buffer, value : Bytes) -> Unit {
+pub fn write_bytes(self : T, value : Bytes) -> Unit {
   let val_len = value.length()
   self.grow_if_necessary(self.len + val_len)
   self.bytes.blit(self.len, value, 0, val_len)
@@ -111,7 +111,7 @@ pub fn write_bytes(self : Buffer, value : Bytes) -> Unit {
 ///|
 /// Write a sub-string into buffer.
 pub fn write_substring(
-  self : Buffer,
+  self : T,
   value : String,
   start : Int,
   len : Int
@@ -126,7 +126,7 @@ pub fn write_substring(
 /// Write a sub-string into buffer.
 /// @alert deprecated "Use `Buffer::write_substring` instead"
 pub fn write_sub_string(
-  self : Buffer,
+  self : T,
   value : String,
   start : Int,
   len : Int
@@ -136,7 +136,7 @@ pub fn write_sub_string(
 
 ///|
 /// Write a char into buffer.
-pub fn write_char(self : Buffer, value : Char) -> Unit {
+pub fn write_char(self : T, value : Char) -> Unit {
   self.grow_if_necessary(self.len + 4)
   let inc = self.bytes.set_utf16_char(self.len, value)
   self.len += inc
@@ -144,24 +144,24 @@ pub fn write_char(self : Buffer, value : Char) -> Unit {
 
 ///|
 /// Write a byte into buffer.
-pub fn write_byte(self : Buffer, value : Byte) -> Unit {
+pub fn write_byte(self : T, value : Byte) -> Unit {
   self.grow_if_necessary(self.len + 1)
   self.bytes[self.len] = value
   self.len += 1
 }
 
 ///|
-pub fn reset(self : Buffer) -> Unit {
+pub fn reset(self : T) -> Unit {
   self.bytes = self.initial_bytes
   self.len = 0
 }
 
 ///|
-pub fn to_bytes(self : Buffer) -> Bytes {
+pub fn to_bytes(self : T) -> Bytes {
   Bytes::new(self.len)..blit(0, self.bytes, 0, self.len)
 }
 
 ///|
-pub impl Show for Buffer with output(self, logger) {
+pub impl Show for T with output(self, logger) {
   logger.write_string(self.to_unchecked_string())
 }
diff --git a/buffer/buffer.mbti b/buffer/buffer.mbti
index 389211605..54dccd8a5 100644
--- a/buffer/buffer.mbti
+++ b/buffer/buffer.mbti
@@ -3,8 +3,8 @@ package moonbitlang/core/buffer
 // Values
 
 // Types and methods
-type Buffer
-impl Buffer {
+type T
+impl T {
   is_empty(Self) -> Bool
   length(Self) -> Int
   new(~size_hint : Int = ..) -> Self
@@ -20,7 +20,7 @@ impl Buffer {
   write_sub_string(Self, String, Int, Int) -> Unit //deprecated
   write_substring(Self, String, Int, Int) -> Unit
 }
-impl Show for Buffer
+impl Show for T
 
 // Type aliases