[llvm] [STLExtras] Introduce bind_{front, back}, [not_]equal_to (PR #175056)

[Jakub Kuderski via llvm-commits]

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@@ -205,4 +207,37 @@ TEST(STLForwardCompatTest, IdentityCxx20) {
   static_assert(std::is_same_v<int &&, decltype(identity(int(5)))>);
 }
 
+TEST(STLForwardCompat, BindFrontBindBack) {
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kuhar wrote:

We probably also need tests for bound arg mutation.

https://github.com/llvm/llvm-project/pull/175056