bounded _lru_cache_wrapprer behaves as if typed=True when it wasn't

[mr-nfamous]

BPO	43436
Nosy	@rhettinger, @mr-nfamous

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/rhettinger'
closed_at = <Date 2021-03-08.19:10:18.396>
created_at = <Date 2021-03-08.17:12:28.188>
labels = ['invalid', '3.8']
title = "bounded _lru_cache_wrapprer behaves as if typed=True when it wasn't"
updated_at = <Date 2021-03-08.19:10:18.395>
user = 'https://github.com/mr-nfamous'

bugs.python.org fields:

activity = <Date 2021-03-08.19:10:18.395>
actor = 'rhettinger'
assignee = 'rhettinger'
closed = True
closed_date = <Date 2021-03-08.19:10:18.396>
closer = 'rhettinger'
components = []
creation = <Date 2021-03-08.17:12:28.188>
creator = 'bup'
dependencies = []
files = []
hgrepos = []
issue_num = 43436
keywords = []
message_count = 2.0
messages = ['388271', '388285']
nosy_count = 2.0
nosy_names = ['rhettinger', 'bup']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue43436'
versions = ['Python 3.8']

[mr-nfamous]

Isn't the point of setting typed=True to make it so that e.g. True doesn't register as a hit when there is already a cache entry for 1.0? Assuming that is the case, although this report specifically targets 3.8 I found no indication that what I believe is the cause of this has been fixed in the interim.

def test():
    from functools import lru_cache
    class No1:
        __eq__ = 0 .__eq__
        __hash__ = 0 .__hash__
    class No2:
        __eq__ = (0,).__contains__
        def __hash__(self, /): return hash(0)
    @lru_cache(256, typed=False)
    def test(v): return [v]
    test(No1()), test(No1()), test(0.0), test(0)
    
    print(test.cache_info())
    @lru_cache(256, typed=False)
    def test(v): return [v]
    test(No2()), test(No2()), test(0.0), test(0)
    print(test.cache_info())


    CacheInfo(hits=0, misses=4, maxsize=256, currsize=4)
CacheInfo(hits=2, misses=2, maxsize=256, currsize=2)

[rhettinger]

Thanks for the report, but this isn't a bug.

Setting typed=True guarantees that types are treated as distinct entries.

Setting typed=False means that the implementation MAY ignore the type and only use equality, but it is not required to do so. If it is convenient for the implementation, it may use type to save space. Currently int and str are treated as distinct from other types that may be equal to them.

Likewise, the implementation is allowed to treat different argument patterns as distinct even if they are equal. Currently, we treat pow(2, 5) as distinct from pow(base=2, exp=5) which is itself distinct from pow(exp=5, base=2).