Introduce rust_unop_ind_operation

This adds class rust_unop_ind_operation, which implements UNOP_IND for
Rust.  Rust requires a special case here to handle trait objects.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* rust-lang.c (eval_op_rust_ind): No longer static.  Add "opcode"
	parameter.
	(rust_evaluate_subexp): Update.
	* rust-exp.h (class rust_unop_ind_operation): New.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2021-03-08  Tom Tromey  <tom@tromey.com>
+
+	* rust-lang.c (eval_op_rust_ind): No longer static.  Add "opcode"
+	parameter.
+	(rust_evaluate_subexp): Update.
+	* rust-exp.h (class rust_unop_ind_operation): New.
+
 2021-03-08  Tom Tromey  <tom@tromey.com>
 
 	* rust-lang.c (eval_op_rust_complement, eval_op_rust_array): No

gdb/rust-exp.h

@@ -33,6 +33,11 @@ extern struct value *eval_op_rust_array (struct type *expect_type,
 					 enum exp_opcode opcode,
 					 struct value *ncopies,
 					 struct value *elt);
+extern struct value *eval_op_rust_ind (struct type *expect_type,
+				       struct expression *exp,
+				       enum noside noside,
+				       enum exp_opcode opcode,
+				       struct value *value);
 
 namespace expr
 {
@@ -42,6 +47,26 @@ using rust_unop_compl_operation = unop_operation<UNOP_COMPLEMENT,
 using rust_array_operation = binop_operation<OP_RUST_ARRAY,
 					     eval_op_rust_array>;
 
+/* The Rust indirection operation.  */
+class rust_unop_ind_operation
+  : public unop_ind_operation
+{
+public:
+
+  using unop_ind_operation::unop_ind_operation;
+
+  value *evaluate (struct type *expect_type,
+		   struct expression *exp,
+		   enum noside noside) override
+  {
+    if (noside != EVAL_NORMAL)
+      return unop_ind_operation::evaluate (expect_type, exp, noside);
+
+    value *arg1 = std::get<0> (m_storage)->evaluate (nullptr, exp, noside);
+    return eval_op_rust_ind (expect_type, exp, noside, UNOP_IND, arg1);
+  }
+};
+
 } /* namespace expr */
 
 #endif /* RUST_EXP_H */

gdb/rust-lang.c

@@ -1325,9 +1325,10 @@ rust_subscript (struct type *expect_type, struct expression *exp,
 
 /* A helper function for UNOP_IND.  */
 
-static struct value *
+struct value *
 eval_op_rust_ind (struct type *expect_type, struct expression *exp,
 		  enum noside noside,
+		  enum exp_opcode opcode,
 		  struct value *value)
 {
   gdb_assert (noside == EVAL_NORMAL);
@@ -1521,7 +1522,7 @@ rust_evaluate_subexp (struct type *expect_type, struct expression *exp,
 	    ++*pos;
 	    struct value *value = evaluate_subexp (expect_type, exp, pos,
 						   noside);
-	    result = eval_op_rust_ind (expect_type, exp, noside, value);
+	    result = eval_op_rust_ind (expect_type, exp, noside, op, value);
 	  }
       }
       break;