prevent panic on triggers with declare statements

enginetest/queries/trigger_queries.go

@@ -2204,6 +2204,45 @@ INSERT INTO t0 (v1, v2) VALUES (i, s); END;`,
 			},
 		},
 	},
+
+	{
+		Name: "Trigger with BLOCK and DECLARE",
+		SetUpScript: []string{
+			"create table t (i int primary key);",
+			"create trigger trig before insert on t for each row begin declare x int; select new.i + 10 into x; set new.i = x; end;",
+			//"create trigger trig before insert on t for each row begin declare x int; set x = new.i * 10; set new.i = x; end;",
+		},
+		Assertions: []ScriptTestAssertion{
+			{
+				Skip:  true,
+				Query: "insert into t values (1);",
+				Expected: []sql.Row{
+					{types.NewOkResult(1)},
+				},
+			},
+			{
+				Skip:  true,
+				Query: "insert into t values (2);",
+				Expected: []sql.Row{
+					{types.NewOkResult(1)},
+				},
+			},
+			{
+				Skip:  true,
+				Query: "select * from t;",
+				Expected: []sql.Row{
+					{10},
+				},
+			},
+			{
+				Skip:  true,
+				Query: "select * from t;",
+				Expected: []sql.Row{
+					{20},
+				},
+			},
+		},
+	},
 }
 
 // RollbackTriggerTests are trigger tests that require rollback logic to work correctly

sql/expression/procedurereference.go

@@ -271,7 +271,11 @@ var _ sql.CollationCoercible = (*ProcedureParam)(nil)
 
 // NewProcedureParam creates a new ProcedureParam expression.
 func NewProcedureParam(name string, typ sql.Type) *ProcedureParam {
-	return &ProcedureParam{name: strings.ToLower(name), typ: typ}
+	return &ProcedureParam{
+		name: strings.ToLower(name),
+		typ:  typ,
+		pRef: NewProcedureReference(),
+	}
 }
 
 // Children implements the sql.Expression interface.

sql/plan/declare_variables.go

@@ -40,6 +40,7 @@ func NewDeclareVariables(names []string, typ sql.Type, defaultVal *sql.ColumnDef
 		Names:      names,
 		Type:       typ,
 		DefaultVal: defaultVal,
+		Pref:       expression.NewProcedureReference(),
 	}
 }