ICU-22793 Clang-Tidy: google-readability-casting

[roubert]

https://releases.llvm.org/17.0.1/tools/clang/tools/extra/docs/clang-tidy/checks/google/readability-casting.html

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22793
• Required: The PR title must be prefixed with a JIRA Issue number.
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number.
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[eggrobin]

Having looked at all of icu4c/source/common, this certainly looks like an improvement, considering the static casts mixed with reinterpret casts that were lurking in various places, and the unnecessary casts.

Only 388 more files to look at…

[eggrobin]

Done with icu4c/source/i18n/, only one comment so far.

Miscellaneous thoughts: turning the infamous Chinese calendar cast-with-comment « cast away const » into a const_cast is certainly a very good thing (though I still think we should get rid of them eventually).
Even more so for turning casts without comments into const_casts in icu4c/source/i18n/dtfmtsym.cpp.

263 more files to look at…

[roubert]

Miscellaneous thoughts: turning the infamous Chinese calendar cast-with-comment « cast away const » into a const_cast is certainly a very good thing (though I still think we should get rid of them eventually).

I've already filed ICU-22640 about all the const_cast<…>(this).