[Lang] User-friendly exception when copying between ti.field

[ntlm1686]

Related issue = #2846

Test 0

x = ti.field(ti.f32, (2, 3))
y = ti.field(ti.f32, (2, 3, 4))
x.copy_from(y)

Result 0

Traceback (most recent call last):
ValueError: ti.field shape (2, 3) does not match the source field shape (2, 3, 4)

Test 1

x = ti.field(ti.f32, (2, 3))
y = np.zeros((2, 3))
x.copy_from(y)

Result 1

Traceback (most recent call last):
TypeError: Cannot copy from a non-field object

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[ntlm1686]

/format

[ntlm1686]

@ailzhang

[ailzhang]

/format

[ailzhang]

cc: @ljjsalt the test failures on GPU seem related?

[ailzhang]

name shape doesn't match what's inside the array :P
Using parameterize for dtype should work and pass CI :D

+@ti.test()
+@pytest.mark.parametrize('shape', field_shapes)
+@pytest.mark.parametrize('dtype', [ti.i32, ti.f32])
+def test_field_copy_from(shape, dtype):
+    x = ti.field(dtype=ti.f32, shape=shape)
+    other = ti.field(dtype=dtype, shape=shape)
+    other.fill(1)
+    x.copy_from(other)
+    convert = lambda arr: arr[0] if len(arr) == 1 else arr
+    assert (convert(x.shape) == shape)
+    assert (x.dtype == ti.f32)
+    assert ((x.to_numpy() == 1).all())

[ntlm1686]

@ailzhang
Hi, I finally have time to keep working on this PR, how can I test locally? I have run the pytest script.
Sorry for taking you so long for this PR, this commit should work.

[ailzhang]

LGTM! Thanks a lot for contributing!