drop C array unpacking back into C instead of going back and forth through Python list coercion

Cython/Compiler/Nodes.py

@@ -4830,19 +4830,16 @@ class SingleAssignmentNode(AssignmentNode):
 
     def unroll(self, node, target_size, env):
         from . import ExprNodes, UtilNodes
-        if node.type.is_ctuple:
-            if node.type.size == target_size:
+
         base = node
-                start_node = None
-                stop_node = None
-                step_node = None
-                check_node = None
-            else:
-                error(self.pos, "Unpacking type %s requires exactly %s arguments." % (
-                    node.type, node.type.size))
-                return
+        start_node = stop_node = step_node = check_node = None
+
+        if node.type.is_ctuple:
+            slice_size = node.type.size
 
-        elif node.type.is_ptr:
+        elif node.type.is_ptr or node.type.is_array:
+            while isinstance(node, ExprNodes.SliceIndexNode) and not (node.start or node.stop):
+                base = node = node.base
             if isinstance(node, ExprNodes.SliceIndexNode):
                 base = node.base
                 start_node = node.start
@@ -4875,19 +4872,25 @@ class SingleAssignmentNode(AssignmentNode):
 
                 try:
                     slice_size = (get_const(stop_node, None) - get_const(start_node, 0)) / get_const(step_node, 1)
-                    if target_size != slice_size:
-                        error(self.pos, "Assignment to/from slice of wrong length, expected %d, got %d" % (
-                            slice_size, target_size))
                 except ValueError:
                     error(self.pos, "C array assignment currently requires known endpoints")
                     return
-                check_node = None
+
+            elif node.type.is_array:
+                slice_size = node.type.size
+                if not isinstance(slice_size, (int, long)):
+                    return  # might still work when coercing to Python
             else:
                 return
 
         else:
             return
 
+        if slice_size != target_size:
+            error(self.pos, "Assignment to/from slice of wrong length, expected %s, got %s" % (
+                slice_size, target_size))
+            return
+
         items = []
         base = UtilNodes.LetRefNode(base)
         refs = [base]

tests/run/arrayassign.pyx

@@ -162,7 +162,12 @@ def test_starred_from_array():
     return x, y, z
 
 
+@cython.test_fail_if_path_exists(
+    '//ParallelAssignmentNode//CoerceToPyTypeNode',
+    '//ParallelAssignmentNode//CoerceFromPyTypeNode',
+)
 @cython.test_assert_path_exists(
+    '//ParallelAssignmentNode',
     '//ReturnStatNode//CoerceToPyTypeNode'
 )
 def test_multiple_from_array():
@@ -170,7 +175,6 @@ def test_multiple_from_array():
     >>> test_multiple_from_array()
     (1, 2, 3)
     """
-    # FIXME: copy currently goes through a Python list, even though we infer the right target types
     cdef int[3] a
     a[0] = 1
     a[1] = 2
@@ -179,6 +183,26 @@ def test_multiple_from_array():
     return x, y, z
 
 
+@cython.test_fail_if_path_exists(
+    '//ParallelAssignmentNode//CoerceToPyTypeNode'
+)
+@cython.test_assert_path_exists(
+    '//ParallelAssignmentNode',
+    '//ReturnStatNode//CoerceToPyTypeNode'
+)
+def test_multiple_from_array_full_slice():
+    """
+    >>> test_multiple_from_array_full_slice()
+    (1, 2, 3)
+    """
+    cdef int[3] a
+    a[0] = 1
+    a[1] = 2
+    a[2] = 3
+    x, y, z = a[:]
+    return x, y, z
+
+
 @cython.test_fail_if_path_exists(
     '//ParallelAssignmentNode//CoerceToPyTypeNode'
 )