Avoid "uninitialised" warnings for sizeof and typeid (GH-3631)

Closes #3575

Cython/Compiler/FlowControl.py

@@ -884,6 +884,12 @@ class ControlFlowAnalysis(CythonTransform):
         self.mark_position(node)
         return node
 
+    def visit_SizeofVarNode(self, node):
+        return node
+
+    def visit_TypeidNode(self, node):
+        return node
+
     def visit_IfStatNode(self, node):
         next_block = self.flow.newblock()
         parent = self.flow.block

tests/errors/w_uninitialized.pyx

@@ -112,6 +112,10 @@ def class_py3k_args():
     args = []
     kwargs = {}
 
+def uninitialized_in_sizeof():
+    cdef int i
+    print sizeof(i)
+
 _ERRORS = """
 6:10: local variable 'a' referenced before assignment
 12:11: local variable 'a' might be referenced before assignment

tests/errors/w_uninitialized_cpp.pyx

+# cython: warn.maybe_uninitialized=True
+# mode: error
+# tag: cpp, werror
+
+from cython.operator import typeid
+
+def uninitialized_in_typeid():
+    cdef int i
+    print typeid(i) == typeid(i)
+
+_ERRORS = """
+"""