MAINT: Implement new style promotion for `np.result_type`, etc.

This implements a new style promotion scheme for mutiple inputs
as are passed to `np.result_type`. It should be noted that
result-type heavily relies on "value-based casting" logic/promotion
logic.
This fact is inherited to many places.  When user DTypes are introduced
some of these places should potentially use "weak DType" logic instead
if the input is a Python scalar.
This is *not* yet implemented. It would be necessary to mark these
the same way as is currently done for `np.result_type`.

This type of "marking" will generally be necessary in a few places,
even if may get away with just switching the logic everywhere.

1 files changed, 14 insertions, 0 deletions

diff --git a/numpy/core/include/numpy/ndarraytypes.h b/numpy/core/include/numpy/ndarraytypes.h
index dacb72022..9ff8c9831 100644
--- a/numpy/core/include/numpy/ndarraytypes.h
+++ b/numpy/core/include/numpy/ndarraytypes.h
@@ -856,6 +856,17 @@ typedef int (PyArray_FinalizeFunc)(PyArrayObject *, PyObject *);
  */
 #define NPY_ARRAY_ENSUREARRAY     0x0040
 
+#if defined(NPY_INTERNAL_BUILD) && NPY_INTERNAL_BUILD
+    /*
+     * Dual use the ENSUREARRAY flag, to indicate that this was a converted
+     * python float, int, or complex.
+     * An array using this flag must be a temporary array that can never
+     * leave the C internals of NumPy.  Even if it does, ENSUREARRAY is
+     * absolutely safe to abuse, since it alraedy is be a base class array :).
+     */
+    #define _NPY_ARRAY_WAS_PYSCALAR   0x0040
+#endif  /* NPY_INTERNAL_BUILD */
+
 /*
  * Make sure that the strides are in units of the element size Needed
  * for some operations with record-arrays.
@@ -1867,6 +1878,8 @@ typedef void (PyDataMem_EventHookFunc)(void *inp, void *outp, size_t size,
     typedef PyArray_Descr *(default_descr_function)(PyArray_DTypeMeta *cls);
     typedef PyArray_DTypeMeta *(common_dtype_function)(
             PyArray_DTypeMeta *dtype1, PyArray_DTypeMeta *dtyep2);
+    typedef PyArray_DTypeMeta *(common_dtype_with_value_function)(
+        PyArray_DTypeMeta *dtype1, PyArray_DTypeMeta *dtyep2, PyObject *value);
     typedef PyArray_Descr *(common_instance_function)(
             PyArray_Descr *dtype1, PyArray_Descr *dtyep2);
 
@@ -1925,6 +1938,7 @@ typedef void (PyDataMem_EventHookFunc)(void *inp, void *outp, size_t size,
         is_known_scalar_type_function *is_known_scalar_type;
         default_descr_function *default_descr;
         common_dtype_function *common_dtype;
+        common_dtype_with_value_function *common_dtype_with_value;
         common_instance_function *common_instance;
         /*
          * The casting implementation (ArrayMethod) to convert between two