expression: fix SimpleString's quote method

[zzl0]

Summary

Fix #636

>>> from libcst import *
>>> m = parse_module('''""""foo"""''')
>>> m.body[0].body[0].value.raw_value
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\zsolz\projects\libcst\libcst\_nodes\expression.py", line 682, in raw_value
    quote_len = len(self.quote)
  File "C:\Users\zsolz\projects\libcst\libcst\_nodes\expression.py", line 666, in quote
    raise Exception("Invalid string {self.value}")
Exception: Invalid string {self.value}

Test Plan

1. Unit test
2. Manual test

>>> from libcst import *
>>> m = parse_module('''""""foo"""''')
>>> m.body[0].body[0].value.raw_value
'"foo'

[codecov-commenter]

Codecov Report

Merging #704 (26442dc) into main (6f28c79) will increase coverage by 0.00%.
The diff coverage is 90.90%.

@@           Coverage Diff           @@
##             main     #704   +/-   ##
=======================================
  Coverage   94.79%   94.80%           
=======================================
  Files         246      247    +1     
  Lines       25692    25701    +9     
=======================================
+ Hits        24356    24365    +9     
  Misses       1336     1336           

Impacted Files	Coverage Δ
libcst/_nodes/expression.py	96.66% <50.00%> (ø)
libcst/_nodes/tests/test_simple_string.py	100.00% <100.00%> (ø)

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[zsol]

LGTM, thanks! Let's add that license header before merging

[zzl0]

Thanks @zsol, @lpetre for reviewing the code.

I noticed that we have code like below (link). Just curious why does it need type hint? since quote = "" is more succinct, and both human and machine can easily infer its type is a string.

quote: str = ""

[bgw]

Just curious why does it need type hint?

You're probably right, there's probably no reason for it to be there.

[zzl0]

@bgw thanks for your reply. Yeah, I also think there's probably no reason for it to be there:

1. It can hurt readability (I have seen some code like below).

        a_long_name_name: AVeryLongLongLongLongLongClassName = 
            AVeryLongLongLongLongLongClassName(param1, param2, ...)

2. Statically-typed languages (Rust, C++, Java etc) recommends using type inference for this simple initialization case to improve DevX by reducing the ceremony.