make array slice guard code work for bounds that are unknown at translation time

Cython/Compiler/ExprNodes.py

@@ -4143,47 +4143,77 @@ class SliceIndexNode(ExprNode):
         if not self.base.type.is_array:
             return
         slice_size = self.base.type.size
+        try:
+            total_length = slice_size = int(slice_size)
+        except ValueError:
+            total_length = None
+
         start = stop = None
         if self.stop:
             stop = self.stop.result()
             try:
                 stop = int(stop)
                 if stop < 0:
-                    slice_size = self.base.type.size + stop
+                    if total_length is None:
+                        slice_size = '%s + %d' % (slice_size, stop)
+                    else:
+                        slice_size += stop
                 else:
                     slice_size = stop
                 stop = None
             except ValueError:
                 pass
+
         if self.start:
             start = self.start.result()
             try:
                 start = int(start)
                 if start < 0:
-                    start = self.base.type.size + start
-                slice_size -= start
+                    if total_length is None:
+                        start = '%s + %d' % (self.base.type.size, start)
+                    else:
+                        start += total_length
+                if isinstance(slice_size, (int, long)):
+                    slice_size -= start
+                else:
+                    slice_size = '%s - (%s)' % (slice_size, start)
                 start = None
             except ValueError:
                 pass
-        check = None
-        if slice_size < 0:
-            if target_size > 0:
+
+        runtime_check = None
+        compile_time_check = False
+        try:
+            int_target_size = int(target_size)
+        except ValueError:
+            int_target_size = None
+        else:
+            compile_time_check = isinstance(slice_size, (int, long))
+
+        if compile_time_check and slice_size < 0:
+            if int_target_size > 0:
                 error(self.pos, "Assignment to empty slice.")
-        elif start is None and stop is None:
+        elif compile_time_check and start is None and stop is None:
             # we know the exact slice length
-            if target_size != slice_size:
-                error(self.pos, "Assignment to slice of wrong length, expected %d, got %d" % (
-                        slice_size, target_size))
+            if int_target_size != slice_size:
+                error(self.pos, "Assignment to slice of wrong length, expected %s, got %s" % (
+                      slice_size, target_size))
         elif start is not None:
             if stop is None:
                 stop = slice_size
-            check = "(%s)-(%s)" % (stop, start)
-        else: # stop is not None:
-            check = stop
-        if check:
-            code.putln("if (unlikely((%s) != %d)) {" % (check, target_size))
-            code.putln('PyErr_Format(PyExc_ValueError, "Assignment to slice of wrong length, expected %%" CYTHON_FORMAT_SSIZE_T "d, got %%" CYTHON_FORMAT_SSIZE_T "d", (Py_ssize_t)%d, (Py_ssize_t)(%s));' % (
-                        target_size, check))
+            runtime_check = "(%s)-(%s)" % (stop, start)
+        elif stop is not None:
+            runtime_check = stop
+        else:
+            runtime_check = slice_size
+
+        if runtime_check:
+            code.putln("if (unlikely((%s) != (%s))) {" % (runtime_check, target_size))
+            code.putln(
+                'PyErr_Format(PyExc_ValueError, "Assignment to slice of wrong length,'
+                ' expected %%" CYTHON_FORMAT_SSIZE_T "d, got %%" CYTHON_FORMAT_SSIZE_T "d",'
+                ' (Py_ssize_t)(%s), (Py_ssize_t)(%s));' % (
+                    target_size, runtime_check))
             code.putln(code.error_goto(self.pos))
             code.putln("}")
 

tests/errors/e_arrayassign.pyx

+# mode: error
+
+ctypedef int[1] int_array
+ctypedef int[2] int_array2
+
+
+cdef int_array x, y
+x = y  # not an error
+
+cdef int_array *x_ptr = &x
+x_ptr[0] = y  # not an error
+
+cdef class A:
+    cdef int_array value
+    def __init__(self):
+        self.value = x  # not an error
+
+
+cdef int_array2 z
+z = x  # error
+x = z  # error
+
+cdef enum:
+    SIZE = 2
+
+ctypedef int[SIZE] int_array_dyn
+
+cdef int_array_dyn d
+d = z  # not an error
+
+
+_ERRORS = u"""
+20:2: Assignment to slice of wrong length, expected 2, got 1
+21:2: Assignment to slice of wrong length, expected 1, got 2
+"""

tests/errors/e_ass.pyx

@@ -10,40 +10,8 @@ cdef void foo(obj):
     obj = p2 # error
 
 
-ctypedef int[1] int_array
-
-
-cdef int_array x, y
-x = y  # not an error
-
-cdef int_array *x_ptr = &x
-x_ptr[0] = y  # not an error
-
-cdef class A:
-    cdef int_array value
-    def __init__(self):
-        self.value = x  # not an error
-
-
-ctypedef int[2] int_array2
-
-cdef int_array2 z
-z = x  # error
-
-
-cdef enum:
-    SIZE = 2
-
-ctypedef int[SIZE] int_array_dyn
-
-cdef int_array_dyn d
-d = z  # error
-
-
 _ERRORS = u"""
 7:19: Cannot assign type 'char *' to 'int'
 8:20: Cannot convert Python object to 'int *'
 10:20: Cannot convert 'int *' to Python object
-31:14: Cannot assign type 'int_array' to 'int_array2'
-40:14: Cannot assign type 'int_array2' to 'int_array_dyn'
 """

tests/run/arrayassign.pyx

@@ -226,4 +226,74 @@ def assign_slice_start_end_from_sliced_pointer():
     a[4] = 345
     a[2:4] = v[2:4]
     return (a[0], a[1], a[2], a[3], a[4])
+
+
+def assign_from_longer_array_slice():
+    """
+    >>> assign_from_longer_array_slice()
+    [3, 4, 5]
+    """
+    cdef int[5] a
+    cdef int[3] b
+    a[0] = 1
+    a[1] = 2
+    a[2] = 3
+    a[3] = 4
+    a[4] = 5
+    b[0] = 11
+    b[1] = 12
+    b[2] = 13
+    b = a[2:]
+    return b
 '''
+
+
+def assign_slice_from_shorter_array():
+    """
+    >>> assign_slice_from_shorter_array()
+    [1, 11, 12, 13, 5]
+    """
+    cdef int[5] a
+    cdef int[3] b
+    a[0] = 1
+    a[1] = 2
+    a[2] = 3
+    a[3] = 4
+    a[4] = 5
+    b[0] = 11
+    b[1] = 12
+    b[2] = 13
+    a[1:4] = b
+    return a
+
+
+cdef enum:
+    SIZE = 2
+
+ctypedef int[SIZE] int_array_dyn
+
+
+def assign_ptr_to_unknown_csize():
+    """
+    >>> assign_ptr_to_unknown_csize()
+    [1, 2]
+    """
+    cdef int* v = [1, 2, 3, 4, 5]
+    cdef int_array_dyn d
+    d = v
+    return d
+
+
+def assign_to_wrong_csize():
+    """
+    >>> assign_to_wrong_csize()
+    Traceback (most recent call last):
+    ValueError: Assignment to slice of wrong length, expected 3, got 2
+    """
+    cdef int_array_dyn d
+    cdef int v[3]
+    v[0] = 1
+    v[1] = 2
+    v[2] = 3
+    d = v
+    return d