Better error for non const PartialEq call generated by match

tests/ui/rfcs/rfc-2632-const-trait-impl/match-non-const-eq.rs

@@ -0,0 +1,12 @@
+// revisions: stock gated
+#![cfg_attr(gated, feature(const_trait_impl))]
+
+const fn foo(input: &'static str) {
+    match input {
+        "a" => (), //[gated]~ ERROR can't compare `str` with `str` in const contexts
+        //~^ ERROR cannot match on `str` in constant functions
+        _ => (),
+    }
+}
+
+fn main() {}