Fix Series.from_tensor/2 to use new integer types

This makes the function stop infering the target series dtype and make
it suppport all the new integer signed and unsigned dtypes.

If people want to read a given tensor in a different type, they must
pass the `:dtype` option.

lib/explorer/series.ex

@@ -496,7 +496,17 @@ defmodule Explorer.Series do
   ## Options
 
     * `:backend` - The backend to allocate the series on.
-    * `:dtype` - The dtype of the series, it must match the underlying tensor type.
+    * `:dtype` - The dtype of the series that must match the underlying tensor type.
+
+      The series can have a different dtype if the tensor is compatible with it.
+      For example, a tensor of `{:u, 8}` can represent a series of `:boolean` dtype.
+
+      Here are the list of compatible tensor types and dtypes:
+
+      * `{:u, 8}` tensor as a `:boolean` series.
+      * `{:s, 32}` tensor as a `:date` series.
+      * `{:s, 64}` tensor as a `:time` series.
+      * `{:s, 64}` tensor as a `{:datetime, unit}` or `{:duration, unit}` series.
 
   ## Examples
 
@@ -516,22 +526,27 @@ defmodule Explorer.Series do
         f64 [1.0, 2.0, 3.0]
       >
 
-  Unsigned 8-bit tensors are assumed to be booleans:
-
       iex> tensor = Nx.tensor([1, 0, 1], type: :u8)
       iex> Explorer.Series.from_tensor(tensor)
       #Explorer.Series<
         Polars[3]
-        boolean [true, false, true]
+        u8 [1, 0, 1]
       >
 
-  Signed 32-bit tensors are assumed to be dates:
-
       iex> tensor = Nx.tensor([-719162, 0, 6129], type: :s32)
       iex> Explorer.Series.from_tensor(tensor)
       #Explorer.Series<
         Polars[3]
-        date [0001-01-01, 1970-01-01, 1986-10-13]
+        s32 [-719162, 0, 6129]
+      >
+
+  Booleans can be read from a tensor of `{:u, 8}` type if the dtype is explicitly given:
+
+      iex> tensor = Nx.tensor([1, 0, 1], type: :u8)
+      iex> Explorer.Series.from_tensor(tensor, dtype: :boolean)
+      #Explorer.Series<
+        Polars[3]
+        boolean [true, false, true]
       >
 
   Times are signed 64-bit representing nanoseconds from midnight and
@@ -560,6 +575,8 @@ defmodule Explorer.Series do
     type = Nx.type(tensor)
     {dtype, opts} = Keyword.pop_lazy(opts, :dtype, fn -> Shared.iotype_to_dtype!(type) end)
 
+    dtype = Shared.normalise_dtype!(dtype)
+
     if Shared.dtype_to_iotype!(dtype) != type do
       raise ArgumentError,
             "dtype #{inspect(dtype)} expects a tensor of type #{inspect(Shared.dtype_to_iotype!(dtype))} " <>

lib/explorer/shared.ex

@@ -510,10 +510,9 @@ defmodule Explorer.Shared do
   """
   def iotype_to_dtype!(type) do
     case type do
-      {:f, _} -> type
-      {:s, 64} -> {:s, 64}
-      {:u, 8} -> :boolean
-      {:s, 32} -> :date
+      {:f, n} when n in [32, 64] -> type
+      {:s, n} when n in [8, 16, 32, 64] -> type
+      {:u, n} when n in [8, 16, 32, 64] -> type
       _ -> raise ArgumentError, "cannot convert binary/tensor type #{inspect(type)} into dtype"
     end
   end

test/explorer/data_frame_test.exs

@@ -3310,10 +3310,6 @@ defmodule Explorer.DataFrameTest do
       assert_raise ArgumentError,
                    "cannot convert dtype string into a binary/tensor type",
                    fn -> DF.put(df, :c, i) end
-
-      assert_raise ArgumentError,
-                   "cannot convert binary/tensor type {:u, 32} into dtype",
-                   fn -> DF.put(df, :e, Nx.tensor([1, 2, 3], type: {:u, 32})) end
     end
   end