[clang] [Clang][diagnostics] Improve the diagnostics for chained comparisons (PR #129285)

[Erich Keane via cfe-commits]

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@@ -85,7 +85,7 @@ void f(int x, int y, int z) {
   if ((a<y) != -1) {}// expected-warning {{comparison of constant -1 with boolean expression is always true}}
 
   if ((a<y) == z) {} // no warning
-  if (a>y<z)      {} // expected-error {{comparisons like 'X<=Y<=Z' don't have their mathematical meaning}}
+  if (a>y<z)      {} // expected-error {{comparisons like 'a > y < z' don't have their mathematical meaning}}
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erichkeane wrote:

Hmm.... @AaronBallman will probably have to comment here, but I'm not sure this is better?  The point of `comparisons like` here was to simplify the diagnostics to something that is `like` what is there, but not actually.

This patch ends up giving us really awful warning/diagnostics in the case where these are more than simple variables, as its just dumping the entire expression.  So I don't know if I like this patch.

https://github.com/llvm/llvm-project/pull/129285