fix: don't use :same return type for most operators

fix: don't use returns as basis type unless explicitly allowed

lib/ash/expr/expr.ex

@@ -835,14 +835,9 @@ defmodule Ash.Expr do
     {type, constraints}
   end
 
-  def determine_types(mod, values, returns) do
+  def determine_types(mod, values, known_result) do
     Code.ensure_compiled(mod)
 
-    basis =
-      if returns && returns != [:any, :same, {:array, :any}, {:array, :same}] do
-        returns
-      end
-
     name =
       cond do
         function_exported?(mod, :operator, 0) ->
@@ -893,6 +888,27 @@ defmodule Ash.Expr do
         length(typeset) == length(values)
     end)
     |> Enum.find_value({Enum.map(values, fn _ -> nil end), nil}, fn {typeset, returns} ->
+      basis =
+        cond do
+          !returns ->
+            nil
+
+          returns == :same ->
+            known_result
+
+          returns == {:array, :same} ->
+            case known_result do
+              {:array, type} ->
+                type
+
+              _ ->
+                nil
+            end
+
+          true ->
+            nil
+        end
+
       types_and_values =
         if typeset == :same do
           Enum.map(values, &{:same, &1})

lib/ash/query/operator/basic.ex

@@ -20,7 +20,8 @@ defmodule Ash.Query.Operator.Basic do
     div: [
       symbol: :/,
       no_nils: true,
-      evaluate_types: :numbers
+      evaluate_types: :numbers,
+      returns: [:float]
     ],
     concat: [
       symbol: :<>,

lib/ash/query/operator/eq.ex

@@ -11,8 +11,7 @@ defmodule Ash.Query.Operator.Eq do
     operator: :==,
     name: :eq,
     predicate?: true,
-    types: [:any, :same],
-    returns: [:boolean]
+    types: [:any, :same]
 
   def new(left, right) do
     {:ok, struct(__MODULE__, left: left, right: right)}

lib/ash/query/operator/operator.ex

@@ -399,7 +399,15 @@ defmodule Ash.Query.Operator do
       def predicate?, do: unquote(opts[:predicate?] || false)
 
       @impl Ash.Query.Operator
-      def returns, do: unquote(opts[:returns] || [:same])
+      if unquote(opts[:predicate?]) do
+        def returns do
+          Enum.map(List.wrap(unquote(opts[:types])), fn _ -> :boolean end)
+        end
+      else
+        def returns do
+          unquote(opts[:returns] || :unknown)
+        end
+      end
 
       @impl Ash.Query.Operator
       def types do