Fix memoryview type checking issue

Cython/Compiler/PyrexTypes.py

@@ -1495,7 +1495,7 @@ def type_check_function(self, exact=True):
             type_check = "PyMemoryView_Check"
         else:
             type_check = 'Py%s_Check' % type_name.capitalize()
-        if exact and type_name not in ('bool', 'slice', 'Exception'):
+        if exact and type_name not in ('bool', 'slice', 'Exception', 'memoryview'):
             type_check += 'Exact'
         return type_check
 

tests/run/builtin_memory_view.pyx

@@ -4,7 +4,7 @@
 
 from __future__ import print_function
 
-import sys
+import io
 
 cimport cython
 #from cpython.memoryview cimport PyMemoryView_GET_BUFFER
@@ -59,3 +59,16 @@ def test_in_with(x):
     """
     with memoryview(x) as xv:
         print(xv[1])
+
+
+def test_returned_type():
+    """
+    This is really just a compile test. An optimization was being
+    applied in a way that generated invalid code
+    >>> test_returned_type()
+    98
+    """
+    def foo() -> memoryview:
+        return io.BytesIO(b"abc").getbuffer()
+
+    print(foo()[1])