Fix and test memoryview indexing performance_hint

Fixes cython#5771

Cython/Compiler/ExprNodes.py

@@ -4965,7 +4965,7 @@ def analyse_types(self, env, getting=True):
 
             elif index.type.is_int or index.type.is_pyobject:
                 if index.type.is_pyobject and not self.warned_untyped_idx:
-                    performance_hint(index.pos, "Index should be typed for more efficient access")
+                    performance_hint(index.pos, "Index should be typed for more efficient access", env)
                     MemoryViewIndexNode.warned_untyped_idx = True
 
                 self.is_memview_index = True

tests/memoryview/memoryview.pyx

@@ -1,4 +1,5 @@
 # mode: run
+# tag: perf_hints
 
 # Test declarations, behaviour and coercions of the memoryview type itself.
 
@@ -1298,3 +1299,21 @@ def test_assignment_typedef():
     y = x
     for v in y:
         print(v)
+
+def test_untyped_index(i):
+    """
+    >>> test_untyped_index(2)
+    3
+    >>> test_untyped_index(0)
+    5
+    >>> test_untyped_index(-1)
+    0
+    """
+    cdef int[6] arr
+    arr = [5, 4, 3, 2, 1, 0]
+    cdef int[:] mview_arr = arr
+    return mview_arr[i]  # should generate a performance hint
+
+_PERFORMANCE_HINTS = """
+1315:21: Index should be typed for more efficient access
+"""