Redeclaring `main` doesn't trigger an error

Adding "int main = 0;" before setup() deny any TX Data from your arduino, could anybody confirm it please or if you can explain it :D

Reproduce the reported Arduino sketch with `int main = 0;` before `setup()` and check whether TX data is denied. Start by tracing how the IDE compiles declarations around `setup()`; done means confirming the behavior and documenting whether a diagnostic is expected.

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