use to_lowercase in str downcase

[amtoine]

Description

as we can see in the documentation of str.to_lowercase, not only ASCII symbols have lower and upper variants.

• str upcase uses the correct method to convert the string
  

  nushell/crates/nu-command/src/strings/str_/case/upcase.rs

  Line 93 in 7ac5a01

  Value::String { val: s, .. } => Value::string(s.to_uppercase(), head),

• str downcase incorrectly converts only ASCII characters
  

  nushell/crates/nu-command/src/strings/str_/case/downcase.rs

  Line 124 in 7ac5a01

  Value::String { val, .. } => Value::string(val.to_ascii_lowercase(), head),

this PR uses str.to_lower_case instead of str.to_ascii_lowercase in str downcase.

User-Facing Changes

• upcase still works fine

~ l> "ὀδυσσεύς" | str upcase
ὈΔΥΣΣΕΎΣ

• downcase now works

👉 before

~ l> "ὈΔΥΣΣΕΎΣ" | str downcase
ὈΔΥΣΣΕΎΣ

👉 after

~ l> "ὈΔΥΣΣΕΎΣ" | str downcase
ὀδυσσεύς

Tests + Formatting

• 🟢 toolkit fmt
• 🟢 toolkit clippy
• ⚫ toolkit test
• ⚫ toolkit test stdlib

adds two tests

• non_ascii_upcase
• non_ascii_downcase

After Submitting

[fdncred]

I think this is technically a breaking change, but aren't all bug fixes breaking changes?

[sholderbach]

Tell me muse, of the deeds of the Unicode which travelled to many scripts after the destruction of U+FFFD

ὀδυσσεύς

[amtoine]

I think this is technically a breaking change, but aren't all bug fixes breaking changes?

i would say every fix is a repearing-change rather than a breaking-change 😉

[amtoine]

let's go with this then 🙏