fixes for JSON traces

* type is now lhs_type to avoid the ambiguity between the lhs symbol and the
  full lhs.

* assignments are now actually added

* The trace ends when the property is violated

* The new member state_var indicates whether the assignment is to a state
  variable or not.

Author: kroening

regression/ebmc/traces/json1.desc

@@ -0,0 +1,15 @@
+CORE
+json1.v
+--bound 10 --json-result -
+^      "identifier": "Verilog::main\.property\.p1",$
+^      "status": "REFUTED",$
+^      "trace": \{$
+^        "states": \[ \[$
+^              "lhs": "main\.data",$
+^              "lhs_type": "\[31:0\]",$
+^              "value": "1"$
+^              "value": "2"$
+^EXIT=10$
+^SIGNAL=0$
+--
+^warning: ignoring

regression/ebmc/traces/json1.v

@@ -0,0 +1,11 @@
+module main(input clk);
+
+  reg [31:0] data;
+  initial data = 1;
+
+  always @(posedge clk)
+    data = data + 1;
+
+  always assert p1: data == 1;
+
+endmodule

src/trans-netlist/trans_trace.cpp

@@ -294,6 +294,9 @@ jsont json(const trans_tracet &trace, const namespacet &ns)
       DATA_INVARIANT(a.lhs.id() == ID_symbol, "assignment lhs must be symbol");
       const symbolt &symbol = ns.lookup(to_symbol_expr(a.lhs));
 
+      if(symbol.is_auxiliary)
+        continue; // drop
+
       std::string lhs_string = from_expr(ns, symbol.name, a.lhs);
 
       std::string value_string =
@@ -307,14 +310,20 @@ jsont json(const trans_tracet &trace, const namespacet &ns)
       json_assignment["display_name"] =
         json_stringt(id2string(symbol.display_name()));
       json_assignment["value"] = json_stringt(value_string);
-      json_assignment["type"] = json_stringt(type_string);
+      json_assignment["lhs_type"] = json_stringt(type_string);
       json_assignment["mode"] = json_stringt(id2string(symbol.mode));
+      json_assignment["state_var"] = jsont::json_boolean(symbol.is_state_var);
 
       if(a.location.is_not_nil())
         json_assignment["location"] = json(a.location);
+
+      json_assignments.push_back(std::move(json_assignment));
     }
 
     json_states.push_back(std::move(json_assignments));
+
+    if(state.property_failed)
+      break; // done
   }
 
   return std::move(json_trace);