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Although the current text does not require narrowing return expressions of the same type as the function, it does not clearly state what is allowed. Is it allowed to narrow the result? Is it allowed to narrow the result sometimes but not always? Is it allowed to partially narrow the result (for example, if the ABI returns floats in double format, but a float function has a float return expression evaluated to wider than double)? An aggressive implementation could argue yes yes to all these questions, though the resulting behavior would complicate debugging and error analysis.
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