warn about unreachable except-else clause

--HG--
extra : amend_source : 4c6b14a416f49c6942dc5fafc87b1ea2120bac7b

Cython/Compiler/ParseTreeTransforms.py

@@ -2164,7 +2164,9 @@ class RemoveUnreachableCode(CythonTransform):
 
     def visit_TryExceptStatNode(self, node):
         self.visitchildren(node)
-        if node.body.is_terminator:
+        if node.body.is_terminator and node.else_clause:
+            if self.current_directives['warn.unreachable']:
+                warning(node.else_clause.pos, "Unreachable code", 2)
             node.else_clause = None
         return node
 

tests/errors/w_unreachable.pyx

@@ -23,9 +23,19 @@ def conditional(a, b):
         return 3
     print 'oops'
 
+def try_except():
+    try:
+        raise TypeError
+    except ValueError:
+        pass
+    else:
+        print 'unreachable'
+
+
 _ERRORS = """
 6:4: Unreachable code
 11:8: Unreachable code
 15:8: Unreachable code
 24:4: Unreachable code
+32:8: Unreachable code
 """