Fixes #998

This change fixes formation of TypeError message string.

Also improved dtype argument validation.

Author: oleksandr-pavlyk

dpctl/tensor/_types.pxi

@@ -102,28 +102,29 @@ cdef str _make_typestr(int typenum):
     return type_to_str[typenum] + str(type_bytesize(typenum))
 
 
-cdef int typenum_from_format(str s) except *:
+cdef int typenum_from_format(str s):
     """
     Internal utility to convert string describing type format
 
     Format is [<|=>][biufc]#
     Shortcuts for formats are i, u, d, D
     """
     if not s:
-        raise TypeError("Format string '" + s + "' cannot be empty.")
+        return -1
     try:
         dt = np.dtype(s)
-    except Exception as e:
-        raise TypeError("Format '" + s + "' is not understood.") from e
+    except Exception:
+        return -1
     if (dt.byteorder == ">"):
-        raise TypeError("Format '" + s + "' can only have native byteorder.")
+        return -2
     return dt.num
 
+
 cdef int descr_to_typenum(object dtype):
     "Returns typenum for argumentd dtype that has attribute descr, assumed numpy.dtype"
     obj = getattr(dtype, 'descr')
     if (not isinstance(obj, list) or len(obj) != 1):
-        return -1
+        return -1    # token for ValueError
     obj = obj[0]
     if (not isinstance(obj, tuple) or len(obj) != 2 or obj[0]):
         return -1
@@ -143,9 +144,11 @@ cdef int dtype_to_typenum(dtype) except *:
     else:
         try:
             dt = np.dtype(dtype)
-            if hasattr(dt, 'descr'):
-                return descr_to_typenum(dt)
-            else:
-                return -1
+        except TypeError:
+            return -3
         except Exception:
             return -1
+        if hasattr(dt, 'descr'):
+            return descr_to_typenum(dt)
+        else:
+            return -3  # token for TypeError

dpctl/tensor/_usmarray.pyx

@@ -188,9 +188,15 @@ cdef class usm_ndarray:
                 raise TypeError("Argument shape must be a list or a tuple.")
         nd = len(shape)
         typenum = dtype_to_typenum(dtype)
+        if (typenum < 0):
+            if typenum == -2:
+                raise ValueError("Data type '" + str(dtype) + "' can only have native byteorder.")
+            elif typenum == -1:
+                raise ValueError("Data type '" + str(dtype) + "' is not understood.")
+            raise TypeError(f"Expected string or a dtype object, got {type(dtype)}")
         itemsize = type_bytesize(typenum)
         if (itemsize < 1):
-            raise TypeError("dtype=" + dtype + " is not supported.")
+            raise TypeError("dtype=" + np.dtype(dtype).name + " is not supported.")
         # allocate host C-arrays for shape, strides
         err = _from_input_shape_strides(
             nd, shape, strides, itemsize, <char> ord(order),