From f38d4951f6265ab6f9659515a39e18030b6a94fe Mon Sep 17 00:00:00 2001
From: archibate <17721388340@163.com>
Date: Wed, 3 Jun 2020 17:00:19 +0800
Subject: [PATCH 1/7] [Lang] [refactor] shows an error if not called from
 correct Taichi/Python-scope

---
 python/taichi/lang/expr.py   | 13 +++++++++++--
 python/taichi/lang/matrix.py | 35 +++++++++++++++++++++++++++++++++--
 python/taichi/lang/util.py   | 26 ++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 4 deletions(-)

diff --git a/python/taichi/lang/expr.py b/python/taichi/lang/expr.py
index 83332b710f3b7..3009607755244 100644
--- a/python/taichi/lang/expr.py
+++ b/python/taichi/lang/expr.py
@@ -37,6 +37,7 @@ def __init__(self, *args, tb=None):
         self.grad = None
         self.val = self
 
+    @python_scope
     def __setitem__(self, key, value):
         if not Expr.layout_materialized:
             self.materialize_layout_callback()
@@ -50,9 +51,8 @@ def __setitem__(self, key, value):
                      (taichi_lang_core.get_max_num_indices() - len(key)))
         self.setter(value, *key)
 
+    @python_scope
     def __getitem__(self, key):
-        import taichi as ti
-        assert not ti.get_runtime().inside_kernel
         if not Expr.layout_materialized:
             self.materialize_layout_callback()
         self.initialize_accessor()
@@ -70,6 +70,7 @@ def loop_range(self):
     def serialize(self):
         return self.ptr.serialize()
 
+    @python_scope
     def initialize_accessor(self):
         if self.getter:
             return
@@ -103,16 +104,19 @@ def setter(value, *key):
         self.getter = getter
         self.setter = setter
 
+    @python_scope
     def set_grad(self, grad):
         self.grad = grad
         self.ptr.set_grad(grad.ptr)
 
+    @python_scope
     def clear(self, deactivate=False):
         assert not deactivate
         node = self.ptr.snode().parent
         assert node
         node.clear_data()
 
+    @python_scope
     def fill(self, val):
         # TODO: avoid too many template instantiations
         from .meta import fill_tensor
@@ -145,6 +149,7 @@ def shape(self):
     def data_type(self):
         return self.snode().data_type()
 
+    @python_scope
     def to_numpy(self):
         from .meta import tensor_to_ext_arr
         import numpy as np
@@ -155,6 +160,7 @@ def to_numpy(self):
         ti.sync()
         return arr
 
+    @python_scope
     def to_torch(self, device=None):
         from .meta import tensor_to_ext_arr
         import torch
@@ -166,6 +172,7 @@ def to_torch(self, device=None):
         ti.sync()
         return arr
 
+    @python_scope
     def from_numpy(self, arr):
         assert self.dim() == len(arr.shape)
         s = self.shape()
@@ -178,9 +185,11 @@ def from_numpy(self, arr):
         import taichi as ti
         ti.sync()
 
+    @python_scope
     def from_torch(self, arr):
         self.from_numpy(arr.contiguous())
 
+    @python_scope
     def copy_from(self, other):
         assert isinstance(other, Expr)
         from .meta import tensor_to_tensor
diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index 14f45b8448c8c..f738217c48b79 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -3,7 +3,7 @@
 import copy
 import numbers
 import numpy as np
-from .util import to_numpy_type, to_pytorch_type, deprecated
+from .util import *
 from .common_ops import TaichiOperations
 from collections.abc import Iterable
 
@@ -144,6 +144,7 @@ def is_global(self):
                 0], "Matrices with mixed global/local entries are not allowed"
         return results[0]
 
+    @taichi_scope
     def element_wise_binary(self, foo, other):
         ret = self.empty_copy()
         if isinstance(other, (list, tuple)):
@@ -163,12 +164,14 @@ def element_wise_binary(self, foo, other):
                 ret.entries[i] = foo(self.entries[i], other)
         return ret
 
+    @taichi_scope
     def element_wise_unary(self, foo):
         ret = self.empty_copy()
         for i in range(self.n * self.m):
             ret.entries[i] = foo(self.entries[i])
         return ret
 
+    @taichi_scope
     def __matmul__(self, other):
         assert self.m == other.n
         ret = Matrix(self.n, other.m)
@@ -243,6 +246,7 @@ def __setitem__(self, key, value):
             self.mat(*key)[self.index] = value
 
     # host access
+    @python_scope
     def __getitem__(self, index):
         return Matrix.Proxy(self, index)
         ret = [[] for _ in range(self.n)]
@@ -252,6 +256,7 @@ def __getitem__(self, index):
         return ret
 
     # host access
+    @python_scope
     def __setitem__(self, index, item):
         if not isinstance(item[0], list):
             item = [[i] for i in item]
@@ -270,11 +275,13 @@ def copy(self):
         ret.entries = copy.copy(self.entries)
         return ret
 
+    @taichi_scope
     def variable(self):
         ret = self.copy()
         ret.entries = [impl.expr_init(e) for e in ret.entries]
         return ret
 
+    @taichi_scope
     def cast(self, dt):
         ret = self.copy()
         if type(dt) is type and issubclass(dt, numbers.Number):
@@ -289,6 +296,7 @@ def cast(self, dt):
             ret.entries[i] = impl.cast(ret.entries[i], dt)
         return ret
 
+    @taichi_scope
     def trace(self):
         assert self.n == self.m
         sum = expr.Expr(self(0, 0))
@@ -296,6 +304,7 @@ def trace(self):
             sum = sum + self(i, i)
         return sum
 
+    @taichi_scope
     def inverse(self):
         assert self.n == self.m, 'Only square matrices are invertible'
         if self.n == 1:
@@ -349,6 +358,7 @@ def E(x, y):
 
     inversed = deprecated('a.inversed()', 'a.inverse()')(inverse)
 
+    @taichi_scope
     def normalized(self, eps=0):
         assert self.m == 1
         invlen = 1.0 / (Matrix.norm(self) + eps)
@@ -363,6 +373,7 @@ def transposed(a):
     def T(self):
         return self.transpose()
 
+    @taichi_scope
     def transpose(a):
         ret = Matrix(a.m, a.n, empty=True)
         for i in range(a.n):
@@ -370,6 +381,7 @@ def transpose(a):
                 ret.set_entry(j, i, a(i, j))
         return ret
 
+    @taichi_scope
     def determinant(a):
         if a.n == 2 and a.m == 2:
             return a(0, 0) * a(1, 1) - a(0, 1) * a(1, 0)
@@ -429,32 +441,37 @@ def make_grad(self):
             ret.entries[i] = self.entries[i].grad
         return ret
 
+    @taichi_scope
     def sum(self):
         ret = self.entries[0]
         for i in range(1, len(self.entries)):
             ret = ret + self.entries[i]
         return ret
 
+    @taichi_scope
     def norm(self, l=2, eps=0):
         assert l == 2
         return impl.sqrt(self.norm_sqr() + eps)
 
-    # TODO: avoid using sqr here since people might consider "sqr" as "square root". New name TBD.
+    @taichi_scope
     def norm_sqr(self):
         return (self**2).sum()
 
+    @taichi_scope
     def max(self):
         ret = self.entries[0]
         for i in range(1, len(self.entries)):
             ret = impl.max(ret, self.entries[i])
         return ret
 
+    @taichi_scope
     def min(self):
         ret = self.entries[0]
         for i in range(1, len(self.entries)):
             ret = impl.min(ret, self.entries[i])
         return ret
 
+    @taichi_scope
     def any(self):
         import taichi as ti
         ret = (self.entries[0] != ti.expr_init(0))
@@ -462,6 +479,7 @@ def any(self):
             ret = ret + (self.entries[i] != ti.expr_init(0))
         return -(ret < ti.expr_init(0))
 
+    @taichi_scope
     def all(self):
         import taichi as ti
         ret = self.entries[0] != ti.expr_init(0)
@@ -497,6 +515,7 @@ def assign_renamed(x, y):
         from .meta import fill_matrix
         fill_matrix(self, val)
 
+    @python_scope
     def to_numpy(self, keep_dims=False):
         # Discussion: https://github.com/taichi-dev/taichi/pull/1046#issuecomment-633548858
         as_vector = self.m == 1 and not keep_dims
@@ -510,6 +529,7 @@ def to_numpy(self, keep_dims=False):
         ti.sync()
         return ret
 
+    @python_scope
     def to_torch(self, device=None, keep_dims=False):
         import torch
         as_vector = self.m == 1 and not keep_dims
@@ -524,6 +544,7 @@ def to_torch(self, device=None, keep_dims=False):
         ti.sync()
         return ret
 
+    @python_scope
     def from_numpy(self, ndarray):
         if len(ndarray.shape) == self.loop_range().dim() + 1:
             as_vector = True
@@ -538,9 +559,11 @@ def from_numpy(self, ndarray):
         import taichi as ti
         ti.sync()
 
+    @python_scope
     def from_torch(self, torch_tensor):
         return self.from_numpy(torch_tensor.contiguous())
 
+    @taichi_scope
     def __ti_repr__(self):
         if self.m != 1:
             yield '['
@@ -559,18 +582,21 @@ def __ti_repr__(self):
             yield ']'
 
     @staticmethod
+    @taichi_scope
     def zero(dt, n, m=1):
         import taichi as ti
         return ti.Matrix([[ti.cast(0, dt) for _ in range(m)]
                           for _ in range(n)])
 
     @staticmethod
+    @taichi_scope
     def one(dt, n):
         import taichi as ti
         return ti.Matrix([[ti.cast(1, dt) for _ in range(n)]
                           for _ in range(n)])
 
     @staticmethod
+    @taichi_scope
     def unit(n, i, dt=None):
         import taichi as ti
         if dt is None:
@@ -579,12 +605,14 @@ def unit(n, i, dt=None):
         return ti.Matrix([ti.cast(int(j == i), dt) for j in range(n)])
 
     @staticmethod
+    @taichi_scope
     def identity(dt, n):
         import taichi as ti
         return ti.Matrix([[ti.cast(int(i == j), dt) for j in range(n)]
                           for i in range(n)])
 
     @staticmethod
+    @taichi_scope
     def rotation2d(alpha):
         import taichi as ti
         return ti.Matrix([[ti.cos(alpha), -ti.sin(alpha)],
@@ -596,11 +624,13 @@ def __hash__(self):
         # using matrices as template arguments.
         return id(self)
 
+    @taichi_scope
     def dot(self, other):
         assert self.m == 1
         assert other.m == 1
         return (self.transpose() @ other).subscript(0, 0)
 
+    @taichi_scope
     def cross(self, b):
         if self.n == 3 and self.m == 1 and b.n == 3 and b.m == 1:
             return Matrix([
@@ -617,6 +647,7 @@ def cross(self, b):
                 "Cross product is only supported between pairs of 2D/3D vectors"
             )
 
+    @taichi_scope
     def outer_product(self, b):
         assert self.m == 1
         assert b.m == 1
diff --git a/python/taichi/lang/util.py b/python/taichi/lang/util.py
index cc03018c3146c..3b90f3a462994 100644
--- a/python/taichi/lang/util.py
+++ b/python/taichi/lang/util.py
@@ -177,3 +177,29 @@ def wrapped(*args, **kwargs):
         return wrapped
 
     return decorator
+
+
+def taichi_scope(func):
+    import functools
+    from . import impl
+
+    @functools.wraps(func)
+    def wrapped(*args, **kwargs):
+        assert impl.inside_kernel(), \
+                f'{func.__name__} cannot be called in Python-scope'
+        return func(*args, **kwargs)
+
+    return wrapped
+
+
+def python_scope(func):
+    import functools
+    from . import impl
+
+    @functools.wraps(func)
+    def wrapped(*args, **kwargs):
+        assert not impl.inside_kernel(), \
+                f'{func.__name__} cannot be called in Taichi-scope'
+        return func(*args, **kwargs)
+
+    return wrapped

From 316a34a6d4fad58aff72906e7f0d95e3f02ee0dc Mon Sep 17 00:00:00 2001
From: archibate <17721388340@163.com>
Date: Wed, 3 Jun 2020 19:03:49 +0800
Subject: [PATCH 2/7] [skip ci] fix deprecation warning (instead of raising
 error)

---
 python/taichi/lang/matrix.py | 6 +++++-
 python/taichi/lang/util.py   | 3 +--
 python/taichi/misc/gui.py    | 2 +-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index f738217c48b79..59747b677ffb1 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -516,8 +516,12 @@ def assign_renamed(x, y):
         fill_matrix(self, val)
 
     @python_scope
-    def to_numpy(self, keep_dims=False):
+    def to_numpy(self, keep_dims=False, as_vector=None):
         # Discussion: https://github.com/taichi-dev/taichi/pull/1046#issuecomment-633548858
+        if as_vector is not None:
+            import warnings
+            warnings.warn('v.to_numpy(as_vector=True) is deprecated, '
+            'please use v.to_numpy() directly instead', DeprecationWarning)
         as_vector = self.m == 1 and not keep_dims
         dim_ext = (self.n, ) if as_vector else (self.n, self.m)
         ret = np.empty(self.loop_range().shape() + dim_ext,
diff --git a/python/taichi/lang/util.py b/python/taichi/lang/util.py
index 3b90f3a462994..ead52db86b851 100644
--- a/python/taichi/lang/util.py
+++ b/python/taichi/lang/util.py
@@ -170,8 +170,7 @@ def decorator(foo):
         def wrapped(*args, **kwargs):
             import warnings
             msg = f'{old} is deprecated, please use {new} instead'
-            #warnings.warn(msg, DeprecationWarning)
-            raise DeprecationWarning(msg)
+            warnings.warn(msg, DeprecationWarning)
             return foo(*args, **kwargs)
 
         return wrapped
diff --git a/python/taichi/misc/gui.py b/python/taichi/misc/gui.py
index 7267d8eb8d65a..e4e36918de2e9 100644
--- a/python/taichi/misc/gui.py
+++ b/python/taichi/misc/gui.py
@@ -146,7 +146,7 @@ def show(self, file=None):
         self.core.update()
         if file:
             self.core.screenshot(file)
-        self.clear(self.background_color)
+        self.clear()
 
     class EventFilter:
         def __init__(self, *filter):

From 031625c963ba7882d2a904c387d2a6c479883aa0 Mon Sep 17 00:00:00 2001
From: archibate <17721388340@163.com>
Date: Thu, 4 Jun 2020 08:19:48 +0800
Subject: [PATCH 3/7] also use deprecated deco for classkernel & classfunc

---
 python/taichi/lang/kernel.py | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/python/taichi/lang/kernel.py b/python/taichi/lang/kernel.py
index b3375670e63d5..07537710a47dd 100644
--- a/python/taichi/lang/kernel.py
+++ b/python/taichi/lang/kernel.py
@@ -121,11 +121,8 @@ def extract_arguments(self):
             self.argument_names.append(param.name)
 
 
+@deprecated('@ti.classfunc', '@ti.func directly')
 def classfunc(foo):
-    import warnings
-    warnings.warn('@ti.classfunc is deprecated. Please use @ti.func directly.',
-                  DeprecationWarning)
-
     func = Func(foo, classfunc=True)
 
     @functools.wraps(foo)
@@ -545,11 +542,8 @@ def kernel(func):
     return _kernel_impl(func, level_of_class_stackframe=3)
 
 
+@deprecated('@ti.classkernel', '@ti.kernel directly')
 def classkernel(func):
-    import warnings
-    warnings.warn(
-        '@ti.classkernel is deprecated. Please use @ti.kernel directly.',
-        DeprecationWarning)
     return _kernel_impl(func, level_of_class_stackframe=3)
 
 

From b1741650476810e634ee707b7f9bbf233175bdcc Mon Sep 17 00:00:00 2001
From: archibate <17721388340@163.com>
Date: Thu, 4 Jun 2020 08:20:31 +0800
Subject: [PATCH 4/7] [skip ci] format

---
 python/taichi/lang/matrix.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index 59747b677ffb1..5e23018c6389a 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -520,8 +520,9 @@ def to_numpy(self, keep_dims=False, as_vector=None):
         # Discussion: https://github.com/taichi-dev/taichi/pull/1046#issuecomment-633548858
         if as_vector is not None:
             import warnings
-            warnings.warn('v.to_numpy(as_vector=True) is deprecated, '
-            'please use v.to_numpy() directly instead', DeprecationWarning)
+            warnings.warn(
+                'v.to_numpy(as_vector=True) is deprecated, '
+                'please use v.to_numpy() directly instead', DeprecationWarning)
         as_vector = self.m == 1 and not keep_dims
         dim_ext = (self.n, ) if as_vector else (self.n, self.m)
         ret = np.empty(self.loop_range().shape() + dim_ext,

From cca4bc67e1314a96bf724dc838130f52125c5b59 Mon Sep 17 00:00:00 2001
From: archibate <17721388340@163.com>
Date: Thu, 4 Jun 2020 08:49:13 +0800
Subject: [PATCH 5/7] [skip ci] deprecation warning use stacklevel

---
 python/taichi/core/util.py   | 4 ++++
 python/taichi/lang/matrix.py | 3 ++-
 python/taichi/lang/util.py   | 2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/python/taichi/core/util.py b/python/taichi/core/util.py
index 8c97b36b3727d..c103382c7494a 100644
--- a/python/taichi/core/util.py
+++ b/python/taichi/core/util.py
@@ -3,6 +3,7 @@
 import shutil
 import sys
 import ctypes
+import warnings
 from pathlib import Path
 from colorama import Fore, Back, Style
 from taichi.misc.settings import get_output_directory, get_build_directory, get_bin_directory, get_repo_directory, get_runtime_directory
@@ -13,6 +14,9 @@
     print("Current Python version:", sys.version_info)
     exit(-1)
 
+warnings.filterwarnings('always')
+
+
 ti_core = None
 
 
diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index 5e23018c6389a..b1c1460f9366b 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -522,7 +522,8 @@ def to_numpy(self, keep_dims=False, as_vector=None):
             import warnings
             warnings.warn(
                 'v.to_numpy(as_vector=True) is deprecated, '
-                'please use v.to_numpy() directly instead', DeprecationWarning)
+                'please use v.to_numpy() directly instead',
+                DeprecationWarning, stacklevel=3)
         as_vector = self.m == 1 and not keep_dims
         dim_ext = (self.n, ) if as_vector else (self.n, self.m)
         ret = np.empty(self.loop_range().shape() + dim_ext,
diff --git a/python/taichi/lang/util.py b/python/taichi/lang/util.py
index ead52db86b851..acbaa6634d6b1 100644
--- a/python/taichi/lang/util.py
+++ b/python/taichi/lang/util.py
@@ -170,7 +170,7 @@ def decorator(foo):
         def wrapped(*args, **kwargs):
             import warnings
             msg = f'{old} is deprecated, please use {new} instead'
-            warnings.warn(msg, DeprecationWarning)
+            warnings.warn(msg, DeprecationWarning, stacklevel=2)
             return foo(*args, **kwargs)
 
         return wrapped

From 8f189beedae92eba28a2b1c04758be6f59459eec Mon Sep 17 00:00:00 2001
From: Taichi Gardener <taichigardener@gmail.com>
Date: Wed, 3 Jun 2020 20:53:26 -0400
Subject: [PATCH 6/7] [skip ci] enforce code format

---
 python/taichi/core/util.py   | 1 -
 python/taichi/lang/matrix.py | 3 ++-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/python/taichi/core/util.py b/python/taichi/core/util.py
index cd48d6efcb177..d4846f5be71a2 100644
--- a/python/taichi/core/util.py
+++ b/python/taichi/core/util.py
@@ -16,7 +16,6 @@
 
 warnings.filterwarnings('always')
 
-
 ti_core = None
 
 
diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index b1c1460f9366b..dafc86a5a4fc7 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -523,7 +523,8 @@ def to_numpy(self, keep_dims=False, as_vector=None):
             warnings.warn(
                 'v.to_numpy(as_vector=True) is deprecated, '
                 'please use v.to_numpy() directly instead',
-                DeprecationWarning, stacklevel=3)
+                DeprecationWarning,
+                stacklevel=3)
         as_vector = self.m == 1 and not keep_dims
         dim_ext = (self.n, ) if as_vector else (self.n, self.m)
         ret = np.empty(self.loop_range().shape() + dim_ext,

From 39895bbc28be12068bb81e1659e3bf5895cafdd6 Mon Sep 17 00:00:00 2001
From: archibate <17721388340@163.com>
Date: Thu, 4 Jun 2020 09:09:18 +0800
Subject: [PATCH 7/7] [skip ci] more taichi_scope

---
 python/taichi/lang/impl.py   | 10 ++++++++++
 python/taichi/lang/matrix.py |  1 +
 2 files changed, 11 insertions(+)

diff --git a/python/taichi/lang/impl.py b/python/taichi/lang/impl.py
index 9ea33a94869da..617d089489b14 100644
--- a/python/taichi/lang/impl.py
+++ b/python/taichi/lang/impl.py
@@ -6,6 +6,7 @@
 from .util import *
 
 
+@taichi_scope
 def expr_init(rhs):
     import taichi as ti
     if rhs is None:
@@ -29,6 +30,7 @@ def expr_init(rhs):
             return Expr(taichi_lang_core.expr_var(Expr(rhs).ptr))
 
 
+@taichi_scope
 def expr_init_func(rhs):  # temporary solution to allow passing in tensors as
     import taichi as ti
     if isinstance(rhs, Expr) and rhs.ptr.is_global_var():
@@ -45,6 +47,7 @@ def wrap_scalar(x):
         return x
 
 
+@taichi_scope
 def subscript(value, *indices):
     import numpy as np
     if isinstance(value, np.ndarray):
@@ -76,6 +79,7 @@ def subscript(value, *indices):
         return Expr(taichi_lang_core.subscript(value.ptr, indices_expr_group))
 
 
+@taichi_scope
 def chain_compare(comparators, ops):
     assert len(comparators) == len(ops) + 1, \
       f'Chain comparison invoked with {len(comparators)} comparators but {len(ops)} operators'
@@ -180,6 +184,7 @@ def get_runtime():
     return pytaichi
 
 
+@taichi_scope
 def make_constant_expr(val):
     if isinstance(val, int):
         if pytaichi.default_ip == i32:
@@ -229,6 +234,7 @@ def __getattribute__(self, item):
 root = Root()
 
 
+@python_scope
 def var(dt, shape=None, offset=None, needs_grad=False):
     if isinstance(shape, numbers.Number):
         shape = (shape, )
@@ -277,6 +283,7 @@ def __init__(self, soa=False):
 AOS = Layout(soa=False)
 
 
+@python_scope
 def layout(func):
     assert not pytaichi.materialized, "All layout must be specified before the first kernel launch / data access."
     warnings.warn(
@@ -286,6 +293,7 @@ def layout(func):
     pytaichi.layout_functions.append(func)
 
 
+@taichi_scope
 def ti_print(*vars):
     def entry2content(var):
         if isinstance(var, str):
@@ -327,6 +335,7 @@ def fused_string(entries):
     taichi_lang_core.create_print(contentries)
 
 
+@taichi_scope
 def ti_int(var):
     if hasattr(var, '__ti_int__'):
         return var.__ti_int__()
@@ -334,6 +343,7 @@ def ti_int(var):
         return int(var)
 
 
+@taichi_scope
 def ti_float(var):
     if hasattr(var, '__ti_float__'):
         return var.__ti_float__()
diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index dafc86a5a4fc7..8e039e5b98480 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -215,6 +215,7 @@ def place(self, snode):
         for e in self.entries:
             snode.place(e)
 
+    @taichi_scope
     def subscript(self, *indices):
         if self.is_global():
             ret = self.empty_copy()