REF: use fused types for the rest of libjoin
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=h1) Report
> Merging [#23214](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e5196aaac6530dad4fbecbce0e1dd048ebf358ad?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23214/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23214      +/-   ##
==========================================
+ Coverage   92.19%   92.19%   +<.01%     
==========================================
  Files         169      169              
  Lines       50962    50953       -9     
==========================================
- Hits        46984    46976       -8     
+ Misses       3978     3977       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.61% <100%> (ø)` | :arrow_up: |
| #single | `42.27% <33.33%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/23214/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `94.01% <100%> (+0.06%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=footer). Last update [e5196aa...1fde739](https://codecov.io/gh/pandas-dev/pandas/pull/23214?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 lgtm. rebase and ping on green. Hello @jbrockmendel! Thanks for updating the PR.

 - There are no PEP8 issues in the file [`pandas/core/reshape/merge.py`](https://github.com/jbrockmendel/pandas/blob/1fde7392df5aa78fd5ef2642b4f18c03e344913e/pandas/core/reshape/merge.py) !

 - There are no PEP8 issues in the file [`setup.py`](https://github.com/jbrockmendel/pandas/blob/1fde7392df5aa78fd5ef2642b4f18c03e344913e/setup.py) !

 Ping thanks! @jbrockmendel 

maybe declared twice?

```
Compiling pandas/_libs/join.pyx because it changed.
[1/1] Cythonizing pandas/_libs/join.pyx
warning: __pyxutil:33:4: '___pyx_int64_t' redeclared 
warning: __pyxutil:34:4: '___pyx_uint64_t' redeclared 
warning: __pyxutil:33:4: '___pyx_int64_t' redeclared 
warning: __pyxutil:34:4: '___pyx_uint64_t' redeclared 
warning: __pyxutil:33:4: '___pyx_int64_t' redeclared 
warning: __pyxutil:34:4: '___pyx_uint64_t' redeclared 
running build_ext
building 'pandas._libs.join' extension
gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/jreback/miniconda3/envs/pandas/include -arch x86_64 -I/Users/jreback/miniconda3/envs/pandas/include -arch x86_64 -Ipandas/_libs/src/klib -Ip
``` I noticed that too; it isn't clear where it's coming from.  I've been keeping the cython folks up to date on issues we run into, will ask about that one if it keeps coming up. Just wanted to report the same, those warnings got introduced recently. But you think it is a cython issue?