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[mypyc] Don't copy items twice in list(<generator expression>) - #22234
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The special case for list(<generator expression>) only handled sources that allow preallocating the result (such as lists and tuples). For other sources, the generator expression was first compiled into a list, an iterator was created for it, and list() then copied the items into a new list. Compile it as a list comprehension in all cases instead.
…ents Specializers that compile a generator expression argument inline (such as list(), sorted() and str.join()) bypassed the check for unpacking in comprehensions (Python 3.15+), causing an internal compiler error. Skip specializers for such calls, so that the generic path reports the error.
p-sawicki
approved these changes
Oct 20, 2026
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The special case for list() only handled sources
that allow preallocating the result (such as lists and tuples). For other
sources, the generator expression was first compiled into a list, an
iterator was created for it, and list() then copied the items into a new
list. Compile it as a list comprehension in all cases instead.