Unnecessary "Possible loss of precision" warning

[agravier]

Describe the bug
When assigning a constant to a field cell, Taichi emits a warning about possible loss of precision even though it's possible to determine at compile time that this is not the case

To Reproduce

import taichi as ti

ti.init(arch=ti.gpu)
init = ti.field(ti.i8, shape=(2, 3))
init[0, 0] = 1

Log/Screenshots

$ python tests/assign_precision.py
[Taichi] version 1.7.1, llvm 15.0.7, commit 0f143b2f, osx, python 3.10.9
[Taichi] Starting on arch=arm64
[W 07/10/24 11:33:51.553 33474852]
Assign may lose precision: unknown <- i8

Additional comments
Maybe I can just disable this check and runtime warning? It has a performance impact as it's emitted each time I do such an assignment.

[niuiniuin]

I met the exactly same situation. My wild guess is that the type of field cells probably is not recognized in the python scope. Doing the assignment in a taichi kernel can circumvent the warning.

import taichi as ti
ti.init(arch=ti.gpu, offline_cache=False)


init = ti.field(ti.i8, shape=(2, 3))

# init[0, 0] = 1
# print(init)

@ti.kernel
def assign_a_cell():
    init[0, 0] = ti.cast(1, ti.i8)
assign_a_cell()
print(init)

[niuiniuin]

Maybe this issue can be closed. They have fixed this bug in version 1.7.2 (#8553).