moonbitlang · bobzhang · Jun 22, 2025 · Jun 20, 2025
diff --git a/builtin/builtin.mbti b/builtin/builtin.mbti
@@ -533,6 +533,7 @@ fn FixedArray::set_utf16le_char(Self[Byte], Int, Char) -> Int
 fn FixedArray::set_utf8_char(Self[Byte], Int, Char) -> Int
 fn[A] FixedArray::unsafe_blit(Self[A], Int, Self[A], Int, Int) -> Unit
 fn[T] FixedArray::unsafe_get(Self[T], Int) -> T
+fn FixedArray::unsafe_reinterpret_as_bytes(Self[Byte]) -> Bytes
 fn[T] FixedArray::unsafe_set(Self[T], Int, T) -> Unit
 
 fn Bytes::copy(Bytes) -> Bytes

diff --git a/builtin/bytes.mbt b/builtin/bytes.mbt
@@ -14,7 +14,14 @@
 
 ///|
 /// Reinterpret the byte sequence as Bytes.
-fn FixedArray::unsafe_to_bytes(self : FixedArray[Byte]) -> Bytes = "%identity"
+/// 
+/// Notice that this will make the `Bytes` object to be a view of the original
+/// byte sequence, so any modification to the original byte sequence will be
+/// reflected in the `Bytes` object.
+#internal(unsafe, "Creating mutable Bytes")
+pub fn FixedArray::unsafe_reinterpret_as_bytes(
+  self : FixedArray[Byte]
+) -> Bytes = "%identity"
 
 ///| 
 /// Creates a new byte sequence of the specified length, where each byte is
@@ -44,7 +51,7 @@ pub fn Bytes::makei(length : Int, value : (Int) -> Byte) -> Bytes {
   for i in 1..<length {
     arr[i] = value(i)
   }
-  FixedArray::unsafe_to_bytes(arr)
+  FixedArray::unsafe_reinterpret_as_bytes(arr)
 }
 
 ///|
@@ -68,7 +75,7 @@ pub fn Bytes::makei(length : Int, value : (Int) -> Byte) -> Bytes {
 pub fn Bytes::of_string(str : String) -> Bytes {
   FixedArray::make(str.length() * 2, Byte::default())
   ..blit_from_string(0, str, 0, str.length())
-  .unsafe_to_bytes()
+  .unsafe_reinterpret_as_bytes()
 }
 
 ///|

diff --git a/builtin/string.mbt b/builtin/string.mbt
@@ -200,7 +200,7 @@ fn unsafe_substring(str : String, start : Int, end : Int) -> String {
   let len = end - start
   let bytes = FixedArray::make(len * 2, Byte::default())
   bytes.blit_from_string(0, str, start, len)
-  bytes.unsafe_to_bytes().to_unchecked_string()
+  bytes.unsafe_reinterpret_as_bytes().to_unchecked_string()
 }
 
 ///|

diff --git a/builtin/stringbuilder_buffer.mbt b/builtin/stringbuilder_buffer.mbt
@@ -109,14 +109,18 @@ pub impl Logger for StringBuilder with write_substring(
 ///| 
 /// Returns the current content of the StringBuilder as a string.
 pub fn StringBuilder::to_string(self : StringBuilder) -> String {
-  self.data.unsafe_to_bytes().to_unchecked_string(offset=0, length=self.len)
+  self.data
+  .unsafe_reinterpret_as_bytes()
+  .to_unchecked_string(offset=0, length=self.len)
 }
 
 ///|
 /// TODO: improve perf
 pub impl Show for StringBuilder with output(self, logger) {
   logger.write_string(
-    self.data.unsafe_to_bytes().to_unchecked_string(offset=0, length=self.len),
+    self.data
+    .unsafe_reinterpret_as_bytes()
+    .to_unchecked_string(offset=0, length=self.len),
   )
 }