[Dy2stat] Fix Read-Only Attribute as while_loop Output

[zhhsplendid]

PR types

Bug fixes

PR changes

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Describe

Fix Read-Only Attribute as while_loop Output:

Usually, our convert_while_loop will be like:

    [a, b, c] = paddle.jit.dy2static.convert_while_loop(
            condition_name, body_name, [a, b, c])

where a, b, c are in loop_var_names.

However, if loop_var_names contains property such as foo.x, we cannot
assign the attribute as output of convert_while_loop because Python
property is a kind of read-only attribute. To handle the case, we replace
the attributes which are output of convert_while_loop with generated
variables, then if we know the attribute is not read-only at runtime, we
assign the attribute. The created statements are like:

    [a, b, __attribute_variable_1] = paddle.jit.dy2static.convert_while_loop(
            condition_name, body_name, [a, b, foo.x])
    if not isinstance(getattr(type(foo), x, None), property): foo.x = __attribute_variable_1

[paddle-bot-old]

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[zhhsplendid]

Here I had a comment error: "attribute" -> "property"

I will change it in the near future (for example, after reviewer reviews it, or make it as test=document_fix in the next PR) because current commit passes CI tests.

[liym27]

LGTM