added pretty_print_const_expr

Author: w-utter

tests/ui/const-generics/generic_const_exprs/const_kind_expr/issue_114151.rs

@@ -20,7 +20,11 @@ where
     //~^^^ ERROR: function takes 1 generic argument but 2 generic arguments were supplied
     //~^^^^ ERROR: unconstrained generic constant
     //~^^^^^ ERROR: unconstrained generic constant `L + 1 + L`
+<<<<<<< HEAD
     //~^^^^^^ ERROR: unconstrained generic constant `(L - 1) + 1 + L`
+=======
+    //~^^^^^ ERROR: unconstrained generic constant `L + 1`
+>>>>>>> c3f8f3834ae (uh)
 }
 
 fn main() {}

tests/ui/const-generics/generic_const_exprs/const_kind_expr/issue_114151.stderr

@@ -58,7 +58,11 @@ error: unconstrained generic constant `L + 1 + L`
 LL |     foo::<_, L>([(); L + 1 + L]);
    |     ^^^^^^^^^^^
 
+<<<<<<< HEAD
 error: unconstrained generic constant `{const expr}`
+=======
+error: unconstrained generic constant `L + 1`
+>>>>>>> c3f8f3834ae (uh)
   --> $DIR/issue_114151.rs:17:5
    |
 LL |     foo::<_, L>([(); L + 1 + L]);