[clang-tools-extra] [clang-tidy][NFC] Prefer `static constexpr` over `static const` where possible (PR #173406)

[Carlos Galvez via cfe-commits]

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@@ -18,7 +18,7 @@ using namespace clang::ast_matchers;
 
 namespace clang::tidy::modernize {
 
-static const char SpecialFunction[] = "SpecialFunction";
+static constexpr char SpecialFunction[] = "SpecialFunction";
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carlosgalvezp wrote:

Off topic: constant/variables that are just a literal copy of their contents is a bit of an antipattern, since they need to change name anytime the contents change. One might as well just use the literal string where needed instead.

https://github.com/llvm/llvm-project/pull/173406