Process del statements as part of definedness analysis

I'm surprised we got away so long without handling them!

Also, it looks like del statements go through full tuple unpacking --
so you can do something like
del (l[1], [c.b])

src/analysis/function_analysis.cpp

@@ -277,7 +277,6 @@ public:
 
     virtual bool visit_assert(AST_Assert* node) { return true; }
     virtual bool visit_branch(AST_Branch* node) { return true; }
-    virtual bool visit_delete(AST_Delete* node) { return true; }
     virtual bool visit_expr(AST_Expr* node) { return true; }
     virtual bool visit_global(AST_Global* node) { return true; }
     virtual bool visit_invoke(AST_Invoke* node) { return false; }
@@ -287,6 +286,21 @@ public:
     virtual bool visit_raise(AST_Raise* node) { return true; }
     virtual bool visit_return(AST_Return* node) { return true; }
 
+    virtual bool visit_delete(AST_Delete* node) {
+        for (auto t : node->targets) {
+            if (t->type == AST_TYPE::Name) {
+                AST_Name* name = ast_cast<AST_Name>(t);
+                state.erase(name->id);
+            } else {
+                // The CFG pass should reduce all deletes to the "basic" deletes on names/attributes/subscripts.
+                // If not, probably the best way to do this would be to just do a full AST traversal
+                // and look for AST_Name's with a ctx of Del
+                assert(t->type == AST_TYPE::Attribute || t->type == AST_TYPE::Subscript);
+            }
+        }
+        return true;
+    }
+
     virtual bool visit_classdef(AST_ClassDef* node) {
         _doSet(node->name);
         return true;

test/tests/del_multi.py

+# expected: fail
+# - we don't support this functionality yet
+
+def f4():
+    a = 1
+    b = 2
+    del [(a,), b]
+    if 0:
+        print a, b
+    print locals()
+f4()
+
+class C(object):
+    pass
+def f5():
+    c = C()
+    c.a = 1
+    c.b = 2
+    c.c = 3
+    l = range(5)
+    del ([c.a], [c.b], l[3])
+    print hasattr(c, "a")
+    print hasattr(c, "b")
+    print hasattr(c, "c")
+    print l
+f5()

test/tests/del_name.py

@@ -58,3 +58,11 @@ try:
     assert 0
 except NameError, e:
     print e
+
+def f3():
+    a = 1
+    del a
+    if 0:
+        pass
+    print locals()
+f3()