Revert "Allow numbers in literal/1 (#4562)"

This reverts commit 3ab8279.

lib/ecto/query/api.ex

@@ -480,20 +480,17 @@ defmodule Ecto.Query.API do
   def fragment(fragments), do: doc!([fragments])
 
   @doc """
-  Allows a literal identifier or number to be injected into a fragment:
+  Allows a literal identifier to be injected into a fragment:
 
       collation = "es_ES"
       fragment("? COLLATE ?", ^name, literal(^collation))
 
-      limit = 10
-      limit(query, fragment("?", literal(^limit)))
-
-  The example above will inject `collation` and `limit` into the queries as
-  literals instead of query parameters. Note that each different value passed
-  to `literal/1` will emit a different query, which will be independently prepared
-  and cached.
+  The example above will inject `collation` into the query as
+  a literal identifier instead of a query parameter. Note that
+  each different value of `collation` will emit a different query,
+  which will be independently prepared and cached.
   """
-  def literal(literal), do: doc!([literal])
+  def literal(binary), do: doc!([binary])
 
   @doc """
   Allows a list argument to be spliced into a fragment.

lib/ecto/query/builder.ex

@@ -1256,12 +1256,13 @@ defmodule Ecto.Query.Builder do
   @doc """
   Called by escaper at runtime to verify literal in fragments.
   """
-  def literal!(literal) when is_binary(literal), do: literal
-  def literal!(literal) when is_number(literal), do: literal
-
   def literal!(literal) do
-    raise ArgumentError,
-          "literal(^value) expects `value` to be a string or a number, got `#{inspect(literal)}`"
+    if is_binary(literal) do
+      literal
+    else
+      raise ArgumentError,
+            "literal(^value) expects `value` to be a string, got `#{inspect(literal)}`"
+    end
   end
 
   @doc """

test/ecto/query_test.exs

@@ -988,20 +988,9 @@ defmodule Ecto.QueryTest do
                raw: ""
              ] = parts
 
-      query = from p in "posts", limit: fragment("?", literal(^1))
-      assert {:fragment, _, parts} = query.limit.expr
-
-      assert [
-               raw: "",
-               expr: {:literal, _, [1]},
-               raw: ""
-             ] = parts
-
-      assert_raise ArgumentError,
-                   "literal(^value) expects `value` to be a string or a number, got `%{}`",
-                   fn ->
-                     from p in "posts", select: fragment("? COLLATE ?", p.name, literal(^%{}))
-                   end
+      assert_raise ArgumentError, "literal(^value) expects `value` to be a string, got `123`", fn ->
+        from p in "posts", select: fragment("? COLLATE ?", p.name, literal(^123))
+      end
     end
 
     test "supports list splicing" do