[cte] fix issue with invalid cte scope mapping (#2857)

Author: max-hoffman

enginetest/queries/queries.go

@@ -1072,6 +1072,16 @@ Select * from (
  ) dt;`,
 		Expected: []sql.Row{{1}},
 	},
+	{
+		Query: `
+WITH RECURSIVE cte(d) AS (
+  SELECT 0
+  UNION ALL
+  SELECT cte.d + 1 FROM cte limit 3
+)
+SELECT * FROM cte WHERE  d = 2;`,
+		Expected: []sql.Row{{2}},
+	},
 	{
 		// https://github.com/dolthub/dolt/issues/5642
 		Query:    "SELECT count(*) FROM mytable WHERE i = 3720481604718463778705849469618542795;",

enginetest/queries/query_plans.go

@@ -154,6 +154,9 @@ func (b *Builder) buildRecursiveCte(inScope *scope, union *ast.SetOp, name strin
 		}
 		b.renameSource(cteScope, name, columns)
 
+		for _, c := range cteScope.cols {
+			scopeMapping[sql.ColumnId(c.id)] = c.scalarGf()
+		}
 		rTable = plan.NewRecursiveTable(name, recSch)
 		cteScope.node = rTable.WithId(tableId).WithColumns(cols)
 	}