diff --git a/python/taichi/lang/impl.py b/python/taichi/lang/impl.py
index 89c5589b94195..af10efa2d4f18 100644
--- a/python/taichi/lang/impl.py
+++ b/python/taichi/lang/impl.py
@@ -9,8 +9,8 @@
 from taichi.lang._ndrange import GroupedNDRange, _Ndrange
 from taichi.lang.any_array import AnyArray, AnyArrayAccess
 from taichi.lang.enums import SNodeGradType
-from taichi.lang.exception import (TaichiRuntimeError, TaichiSyntaxError,
-                                   TaichiTypeError)
+from taichi.lang.exception import (TaichiCompilationError, TaichiRuntimeError,
+                                   TaichiSyntaxError, TaichiTypeError)
 from taichi.lang.expr import Expr, make_expr_group
 from taichi.lang.field import Field, ScalarField
 from taichi.lang.kernel_arguments import SparseMatrixProxy
@@ -135,6 +135,21 @@ def begin_frontend_if(ast_builder, cond):
     ast_builder.begin_frontend_if(Expr(cond).ptr)
 
 
+@taichi_scope
+def _calc_slice(index, default_stop):
+    start, stop, step = index.start or 0, index.stop or default_stop, index.step or 1
+
+    def check_validity(x):
+        #  TODO(mzmzm): support variable in slice
+        if isinstance(x, Expr):
+            raise TaichiCompilationError(
+                "Taichi does not support variables in slice now, please use constant instead of it."
+            )
+
+    check_validity(start), check_validity(stop), check_validity(step)
+    return [_ for _ in range(start, stop, step)]
+
+
 @taichi_scope
 def subscript(ast_builder,
               value,
diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index 05d2f6d6f7675..fd687fec6c8b4 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -249,10 +249,10 @@ def _subscript(self, is_global_mat, *indices, get_ref=False):
         j = 0 if len(indices) == 1 else indices[1]
         has_slice = False
         if isinstance(i, slice):
-            i = self._calc_slice(i, self.n)
+            i = impl._calc_slice(i, self.n)
             has_slice = True
         if isinstance(j, slice):
-            j = self._calc_slice(j, self.m)
+            j = impl._calc_slice(j, self.m)
             has_slice = True
 
         if has_slice:
@@ -280,19 +280,6 @@ def _subscript(self, is_global_mat, *indices, get_ref=False):
                                          self.dynamic_index_stride)
         return self._get_entry(i, j)
 
-    def _calc_slice(self, index, default_stop):
-        start, stop, step = index.start or 0, index.stop or default_stop, index.step or 1
-
-        def check_validity(x):
-            #  TODO(mzmzm): support variable in slice
-            if isinstance(x, expr.Expr):
-                raise TaichiCompilationError(
-                    "Taichi does not support variables in slice now, please use constant instead of it."
-                )
-
-        check_validity(start), check_validity(stop), check_validity(step)
-        return [_ for _ in range(start, stop, step)]
-
 
 class _MatrixEntriesInitializer:
     def pyscope_or_ref(self, arr):