[clang] [clang][Sema] Warn consecutive builtin comparisons in an expression (PR #92200)

[Aaron Ballman via cfe-commits]

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@@ -215,3 +215,10 @@ namespace PR20735 {
     // fix-it:"{{.*}}":{[[@LINE-9]]:20-[[@LINE-9]]:20}:")"
   }
 }
+
+void consecutive_builtin_compare(int x, int y, int z) {
+  (void)(x < y < z);  // expected-warning {{comparisons like 'X<=Y<=Z' don't have their mathematical meaning}}
+  (void)(x < y > z);  // expected-warning {{comparisons like 'X<=Y<=Z' don't have their mathematical meaning}}
+  (void)(x < y <= z); // expected-warning {{comparisons like 'X<=Y<=Z' don't have their mathematical meaning}}
+  (void)(x <= y > z); // expected-warning {{comparisons like 'X<=Y<=Z' don't have their mathematical meaning}}
----------------
AaronBallman wrote:

> I don't have the capacity to further make clang diagnose case 2 but not case 3.
> I added a TODO note at the bottom of the test lines for now.

SGTM!

https://github.com/llvm/llvm-project/pull/92200