implement unicode safe api for String

[Yu-zh]

Part of #1452

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

Here are three observations and potential issues from the provided git diff output:

1. Redundant Function Definitions:

   • In builtin/intrinsics.mbt, both String::get and String::unsafe_get are defined with the same implementation ("%string_get"). This redundancy might lead to confusion or maintenance issues. Consider whether unsafe_get should have a different implementation or if it should be removed entirely if it serves the same purpose as get.

2. Potential Panic in code_point_at Function:

   • The code_point_at function in string/string.mbt has a loop that increments idx and num, but the else block after the loop assumes that num == index will always be true when the loop exits. However, if the loop exits early due to an invalid surrogate pair, num might not equal index, leading to a panic. This could be a logical error, and the condition should be carefully reviewed to ensure it behaves as expected in all cases.

3. Inconsistent Documentation:

   • The documentation for code_unit_at and code_point_at in string/string.mbt mentions that these functions panic if the index is out of bounds. However, the unsafe_get function, which is used internally, does not have any bounds checking. This inconsistency could lead to confusion or misuse of the unsafe_get function, as users might assume it performs bounds checking like the higher-level functions. Consider adding clear documentation to unsafe_get to indicate that it does not perform bounds checking and should be used with caution.

These issues should be addressed to improve code clarity, maintainability, and correctness.

[coveralls]

Pull Request Test Coverage Report for Build 4744

Details

• 0 of 26 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.4%) to 82.475%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
string/string.mbt	0	26	0.0%

Totals
Change from base Build 4739:	-0.4%
Covered Lines:	4819
Relevant Lines:	5843

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💛 - Coveralls