feat(builtin): add ArrayView::strip_prefix and strip_suffix

builtin/arrayview.mbt

@@ -923,6 +923,56 @@ pub fn[T : Eq] ArrayView::ends_with(
   }
 }
 
+///|
+/// Returns a sub-view with `prefix` removed from the start, or `None` if the
+/// view does not start with `prefix`. The returned view shares the original
+/// backing array — no allocation.
+///
+/// Example:
+///
+/// ```mbt check
+/// test {
+///   let v = [1, 2, 3, 4, 5][:]
+///   inspect(v.strip_prefix([1, 2][:]), content="Some([3, 4, 5])")
+///   inspect(v.strip_prefix([2, 3][:]), content="None")
+/// }
+/// ```
+pub fn[T : Eq] ArrayView::strip_prefix(
+  self : ArrayView[T],
+  prefix : ArrayView[T],
+) -> ArrayView[T]? {
+  if self.starts_with(prefix) {
+    Some(self[prefix.length():])
+  } else {
+    None
+  }
+}
+
+///|
+/// Returns a sub-view with `suffix` removed from the end, or `None` if the
+/// view does not end with `suffix`. The returned view shares the original
+/// backing array — no allocation.
+///
+/// Example:
+///
+/// ```mbt check
+/// test {
+///   let v = [1, 2, 3, 4, 5][:]
+///   inspect(v.strip_suffix([4, 5][:]), content="Some([1, 2, 3])")
+///   inspect(v.strip_suffix([3, 4][:]), content="None")
+/// }
+/// ```
+pub fn[T : Eq] ArrayView::strip_suffix(
+  self : ArrayView[T],
+  suffix : ArrayView[T],
+) -> ArrayView[T]? {
+  if self.ends_with(suffix) {
+    Some(self[:self.length() - suffix.length()])
+  } else {
+    None
+  }
+}
+
 ///|
 /// Performs a binary search on a sorted array view.
 ///

builtin/arrayview_test.mbt

@@ -807,3 +807,74 @@ test "ArrayView::filter_map does not mutate source" {
   let _ = v.filter_map(x => Some(x + 100))
   inspect(arr, content="[1, 2, 3, 4]")
 }
+
+///|
+test "ArrayView::strip_prefix basic" {
+  let v = [1, 2, 3, 4, 5][:]
+  inspect(v.strip_prefix([1, 2][:]), content="Some([3, 4, 5])")
+  inspect(v.strip_prefix([2, 3][:]), content="None")
+}
+
+///|
+test "ArrayView::strip_prefix empty prefix" {
+  let v = [1, 2, 3][:]
+  inspect(v.strip_prefix([][:]), content="Some([1, 2, 3])")
+}
+
+///|
+test "ArrayView::strip_prefix full match" {
+  let v = [1, 2, 3][:]
+  inspect(v.strip_prefix([1, 2, 3][:]), content="Some([])")
+}
+
+///|
+test "ArrayView::strip_prefix too long" {
+  let v = [1, 2][:]
+  inspect(v.strip_prefix([1, 2, 3][:]), content="None")
+}
+
+///|
+test "ArrayView::strip_prefix on sliced view" {
+  let v = [0, 1, 2, 3, 4][1:]
+  inspect(v.strip_prefix([1, 2][:]), content="Some([3, 4])")
+}
+
+///|
+test "ArrayView::strip_prefix shares backing" {
+  let arr = [1, 2, 3, 4, 5]
+  guard arr[:].strip_prefix([1, 2][:]) is Some(rest)
+  // Mutating the source propagates to the stripped view.
+  arr[2] = 99
+  inspect(rest, content="[99, 4, 5]")
+}
+
+///|
+test "ArrayView::strip_suffix basic" {
+  let v = [1, 2, 3, 4, 5][:]
+  inspect(v.strip_suffix([4, 5][:]), content="Some([1, 2, 3])")
+  inspect(v.strip_suffix([3, 4][:]), content="None")
+}
+
+///|
+test "ArrayView::strip_suffix empty suffix" {
+  let v = [1, 2, 3][:]
+  inspect(v.strip_suffix([][:]), content="Some([1, 2, 3])")
+}
+
+///|
+test "ArrayView::strip_suffix full match" {
+  let v = [1, 2, 3][:]
+  inspect(v.strip_suffix([1, 2, 3][:]), content="Some([])")
+}
+
+///|
+test "ArrayView::strip_suffix too long" {
+  let v = [1, 2][:]
+  inspect(v.strip_suffix([0, 1, 2][:]), content="None")
+}
+
+///|
+test "ArrayView::strip_suffix on sliced view" {
+  let v = [0, 1, 2, 3, 4][:4]
+  inspect(v.strip_suffix([2, 3][:]), content="Some([0, 1])")
+}

builtin/pkg.generated.mbti

@@ -225,6 +225,8 @@ pub fn[T : Eq] ArrayView::search(Self[T], T) -> Int?
 pub fn[T] ArrayView::search_by(Self[T], (T) -> Bool raise?) -> Int? raise?
 pub fn[T] ArrayView::start_offset(Self[T]) -> Int
 pub fn[T : Eq] ArrayView::starts_with(Self[T], Self[T]) -> Bool
+pub fn[T : Eq] ArrayView::strip_prefix(Self[T], Self[T]) -> Self[T]?
+pub fn[T : Eq] ArrayView::strip_suffix(Self[T], Self[T]) -> Self[T]?
 pub fn[T] ArrayView::suffixes(Self[T], include_empty? : Bool) -> Iter[Self[T]]
 pub fn[T] ArrayView::to_array(Self[T]) -> Array[T]
 #alias("_[_:_]")