Remove eval_op_concat

eval_op_concat has code to search for an operator overload of
BINOP_CONCAT.  However, the operator overloading code is specific to
C++, which does not have this operator.  And,
binop_types_user_defined_p rejects this case right at the start, and
value_x_binop does not handle this case.  I think this code has been
dead for a very long time.  This patch removes it and hoists the
remaining call into concatenation::evaluate, removing eval_op_concat
entirely.

gdb/eval.c

@@ -1106,18 +1106,6 @@ eval_op_objc_selector (struct type *expect_type, struct expression *exp,
 			     lookup_child_selector (exp->gdbarch, sel));
 }
 
-/* Helper function that implements the body of BINOP_CONCAT.  */
-
-struct value *
-eval_op_concat (struct type *expect_type, struct expression *exp,
-		enum noside noside, struct value *arg1, struct value *arg2)
-{
-  if (binop_user_defined_p (BINOP_CONCAT, arg1, arg2))
-    return value_x_binop (arg1, arg2, BINOP_CONCAT, OP_NULL, noside);
-  else
-    return value_concat (arg1, arg2);
-}
-
 /* A helper function for TERNOP_SLICE.  */
 
 struct value *

gdb/expop.h

@@ -83,10 +83,6 @@ extern struct value *eval_op_member (struct type *expect_type,
 				     struct expression *exp,
 				     enum noside noside,
 				     struct value *arg1, struct value *arg2);
-extern struct value *eval_op_concat (struct type *expect_type,
-				     struct expression *exp,
-				     enum noside noside,
-				     struct value *arg1, struct value *arg2);
 extern struct value *eval_op_add (struct type *expect_type,
 				  struct expression *exp,
 				  enum noside noside,
@@ -1158,7 +1154,7 @@ public:
       = std::get<0> (m_storage)->evaluate_with_coercion (exp, noside);
     value *rhs
       = std::get<1> (m_storage)->evaluate_with_coercion (exp, noside);
-    return eval_op_concat (expect_type, exp, noside, lhs, rhs);
+    return value_concat (lhs, rhs);
   }
 
   enum exp_opcode opcode () const override

gdb/valarith.c

@@ -252,7 +252,7 @@ int
 binop_types_user_defined_p (enum exp_opcode op,
 			    struct type *type1, struct type *type2)
 {
-  if (op == BINOP_ASSIGN || op == BINOP_CONCAT)
+  if (op == BINOP_ASSIGN)
     return 0;
 
   type1 = check_typedef (type1);