Remove incorrect subquery parameter check (#4490)

thanks very much for finding this @zachdaniel and apologies for the bug

lib/ecto/query/planner.ex

@@ -370,11 +370,7 @@ defmodule Ecto.Query.Planner do
     {schema_or_source, expr, %{select: select} = query} =
       rewrite_subquery_select_expr(query, source?)
 
-    {expr, counter} = prewalk(expr, :select, query, select, 0, adapter)
-
-    if counter != length(select.params) do
-      error!(query, "subqueries cannot select_merge onto an existing field that has an interpolation")
-    end
+    {expr, _} = prewalk(expr, :select, query, select, 0, adapter)
 
     {{:map, types}, fields, _from} =
       collect_fields(expr, [], :none, query, select.take, true, %{})

test/ecto/query/subquery_test.exs

@@ -563,14 +563,5 @@ defmodule Ecto.Query.SubqueryTest do
 
       assert Macro.to_string(planned_q.from.source.query.select.expr) == "%{id: ^0, text: ^1}"
     end
-
-    test "overlapping interpolations are allowed" do
-      msg = ~r"subqueries cannot select_merge onto an existing field that has an interpolation"
-
-      assert_raise Ecto.SubQueryError, msg, fn ->
-        q = from c in Comment, select: %{id: ^1}, select_merge: %{id: ^2}
-        from(s in subquery(q)) |> plan()
-      end
-    end
   end
 end