For that assertion in particular I believe I'm practically parroting a ruling by the district court in Oracle vs Google about some extremely simple Java functions that Oracle claimed Google copied. Though I can't say I checked to make sure I'm remembering right.
You're recalling it right, but there's a nice quote from Judge Alsup in that case that talks about this exact situation:
> “So long as the specific code used to implement a method is different, anyone is free under the Copyright Act to write his or her own code to carry out exactly the same function or specification...”
Here given that this is rust and the original expression is C, the implementations cannot be the same by definition.
