Provisional implementation of PEP 3104.

Add nonlocal_stmt to Grammar and Nonlocal node to AST.  They both
parallel the definitions for globals.  The symbol table treats
variables declared as nonlocal just like variables that are free
implicitly.

This change is missing the language spec changes, but makes some
decisions about what the spec should say via the unittests.  The PEP
is silent on a number of decisions, so we should review those before
claiming that nonlocal is complete.

Thomas Wouters made the grammer and ast changes.  Jeremy Hylton added
the symbol table changes and the tests.  Pete Shinners and Neal
Norwitz helped review the code.

1 files changed, 31 insertions, 0 deletions

diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index 5aefbac..7f1640f 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -131,6 +131,10 @@ static PyTypeObject *Global_type;
 static char *Global_fields[]={
         "names",
 };
+static PyTypeObject *Nonlocal_type;
+static char *Nonlocal_fields[]={
+        "names",
+};
 static PyTypeObject *Expr_type;
 static char *Expr_fields[]={
         "value",
@@ -507,6 +511,8 @@ static int init_types(void)
         if (!ImportFrom_type) return 0;
         Global_type = make_type("Global", stmt_type, Global_fields, 1);
         if (!Global_type) return 0;
+        Nonlocal_type = make_type("Nonlocal", stmt_type, Nonlocal_fields, 1);
+        if (!Nonlocal_type) return 0;
         Expr_type = make_type("Expr", stmt_type, Expr_fields, 1);
         if (!Expr_type) return 0;
         Pass_type = make_type("Pass", stmt_type, NULL, 0);
@@ -1146,6 +1152,20 @@ Global(asdl_seq * names, int lineno, int col_offset, PyArena *arena)
 }
 
 stmt_ty
+Nonlocal(asdl_seq * names, int lineno, int col_offset, PyArena *arena)
+{
+        stmt_ty p;
+        p = (stmt_ty)PyArena_Malloc(arena, sizeof(*p));
+        if (!p)
+                return NULL;
+        p->kind = Nonlocal_kind;
+        p->v.Nonlocal.names = names;
+        p->lineno = lineno;
+        p->col_offset = col_offset;
+        return p;
+}
+
+stmt_ty
 Expr(expr_ty value, int lineno, int col_offset, PyArena *arena)
 {
         stmt_ty p;
@@ -2197,6 +2217,15 @@ ast2obj_stmt(void* _o)
                         goto failed;
                 Py_DECREF(value);
                 break;
+        case Nonlocal_kind:
+                result = PyType_GenericNew(Nonlocal_type, NULL, NULL);
+                if (!result) goto failed;
+                value = ast2obj_list(o->v.Nonlocal.names, ast2obj_identifier);
+                if (!value) goto failed;
+                if (PyObject_SetAttrString(result, "names", value) == -1)
+                        goto failed;
+                Py_DECREF(value);
+                break;
         case Expr_kind:
                 result = PyType_GenericNew(Expr_type, NULL, NULL);
                 if (!result) goto failed;
@@ -3049,6 +3078,8 @@ init_ast(void)
             0) return;
         if (PyDict_SetItemString(d, "Global", (PyObject*)Global_type) < 0)
             return;
+        if (PyDict_SetItemString(d, "Nonlocal", (PyObject*)Nonlocal_type) < 0)
+            return;
         if (PyDict_SetItemString(d, "Expr", (PyObject*)Expr_type) < 0) return;
         if (PyDict_SetItemString(d, "Pass", (PyObject*)Pass_type) < 0) return;
         if (PyDict_SetItemString(d, "Break", (PyObject*)Break_type) < 0) return;