[clang] [clang][NFC] move traits to tablegen (PR #201491)

[Erich Keane via cfe-commits]

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@@ -0,0 +1,556 @@
+class Trait<string P> {
+  string Prefix = P;
+  string Spelling = "";
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erichkeane wrote:

Perhaps a separate collection of `alias`es would be useful?  It seems the differentiation between an alias and a name could be reasonably useful.

https://github.com/llvm/llvm-project/pull/201491