Special-case "exec in globals()"

We don't support arbitrary dict-like objects as the globals, but
in the special case that that dict-like object is just an attrwrapper
around the current module, we can fall back on our module-as-globals
support.

src/codegen/irgen/hooks.cpp

@@ -368,6 +368,9 @@ Box* eval(Box* boxedCode) {
     if (globals == module)
         globals = NULL;
 
+    if (globals && globals->cls == attrwrapper_cls && unwrapAttrWrapper(globals) == module)
+        globals = NULL;
+
     // TODO error message if parse fails or if it isn't an expr
     // TODO should have a cleaner interface that can parse the Expression directly
     // TODO this memory leaks
@@ -414,7 +417,10 @@ Box* exec(Box* boxedCode, Box* globals, Box* locals) {
     if (globals == module)
         globals = NULL;
 
-    assert(!globals || globals->cls == dict_cls);
+    if (globals && globals->cls == attrwrapper_cls && unwrapAttrWrapper(globals) == module)
+        globals = NULL;
+
+    ASSERT(!globals || globals->cls == dict_cls, "%s", globals->cls->tp_name);
 
     if (globals) {
         // From CPython (they set it to be f->f_builtins):

src/runtime/types.cpp

@@ -1153,6 +1153,10 @@ public:
 
     DEFAULT_CLASS(attrwrapper_cls);
 
+    Box* getUnderlying() {
+        return b;
+    }
+
     static void gcHandler(GCVisitor* v, Box* b) {
         boxGCHandler(v, b);
 
@@ -1401,6 +1405,11 @@ Box* makeAttrWrapper(Box* b) {
     return new AttrWrapper(b);
 }
 
+Box* unwrapAttrWrapper(Box* b) {
+    assert(b->cls == attrwrapper_cls);
+    return static_cast<AttrWrapper*>(b)->getUnderlying();
+}
+
 Box* attrwrapperKeys(Box* b) {
     return AttrWrapper::keys(b);
 }

src/runtime/types.h

@@ -784,6 +784,7 @@ Box* objectNewNoArgs(BoxedClass* cls);
 Box* objectSetattr(Box* obj, Box* attr, Box* value);
 
 Box* makeAttrWrapper(Box* b);
+Box* unwrapAttrWrapper(Box* b);
 Box* attrwrapperKeys(Box* b);
 
 #define SystemError ((BoxedClass*)PyExc_SystemError)