[Lang] Add errror message for missing init call

python/taichi/lang/impl.py

@@ -490,7 +490,13 @@ def create_field_member(dtype, name):
     dtype = cook_dtype(dtype)
 
     # primal
-    x = Expr(get_runtime().prog.make_id_expr(""))
+    prog = get_runtime().prog
+    if prog is None:
+        raise TaichiRuntimeError(
+            "Cannont create field, maybe you forgot to call `ti.init()` first?"
+        )
+
+    x = Expr(prog.make_id_expr(""))
     x.declaration_tb = get_traceback(stacklevel=4)
     x.ptr = _ti_core.global_new(x.ptr, dtype)
     x.ptr.set_name(name)

python/taichi/lang/ops.py

@@ -7,6 +7,7 @@
 from taichi.lang import expr, impl
 from taichi.lang.exception import TaichiSyntaxError
 from taichi.lang.util import cook_dtype, is_taichi_class, taichi_scope
+from taichi.types.annotations import template
 
 unary_ops = []
 
@@ -375,18 +376,13 @@ def round(x):  # pylint: disable=redefined-builtin
 @unary
 def floor(x):
     """Return the floor of the input, element-wise.
-
     The floor of the scalar `x` is the largest integer `k`, such that `k <= x`.
-
     Args:
         x (Union[:mod:`~taichi.types.primitive_types`, :class:`~taichi.Matrix`]): \
             Input scalar or matrix.
-
     Returns:
         The floor of each element in `x`, with float type.
-
     Example::
-
         >>> @ti.kernel
         >>> def test():
         >>>     x = ti.Matrix([3.14, -1.5])