From 558a016e2c02157aa610ae55e72e14a18e43abc5 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Mon, 7 Sep 2015 16:55:02 +0100
Subject: [PATCH] py/compile: Refine SyntaxError for repeated use of
 global/nonlocal.

---
 py/compile.c                | 10 ++++------
 tests/basics/scope.py       | 21 +++++++++++++++++++++
 tests/basics/syntaxerror.py | 12 ++++++++++--
 3 files changed, 35 insertions(+), 8 deletions(-)
 create mode 100644 tests/basics/scope.py

diff --git a/py/compile.c b/py/compile.c
index 8580c8ce40..34f377fb0c 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -1355,9 +1355,8 @@ STATIC void compile_import_from(compiler_t *comp, mp_parse_node_struct_t *pns) {
 STATIC void compile_declare_global(compiler_t *comp, mp_parse_node_t pn, qstr qst) {
     bool added;
     id_info_t *id_info = scope_find_or_add_id(comp->scope_cur, qst, &added);
-    if (!added) {
-        // TODO this is not compliant with CPython
-        compile_syntax_error(comp, pn, "identifier already used");
+    if (!added && id_info->kind != ID_INFO_KIND_GLOBAL_EXPLICIT) {
+        compile_syntax_error(comp, pn, "identifier redefined as global");
         return;
     }
     id_info->kind = ID_INFO_KIND_GLOBAL_EXPLICIT;
@@ -1382,9 +1381,8 @@ STATIC void compile_global_stmt(compiler_t *comp, mp_parse_node_struct_t *pns) {
 STATIC void compile_declare_nonlocal(compiler_t *comp, mp_parse_node_t pn, qstr qst) {
     bool added;
     id_info_t *id_info = scope_find_or_add_id(comp->scope_cur, qst, &added);
-    if (!added) {
-        // TODO this is not compliant with CPython
-        compile_syntax_error(comp, pn, "identifier already used");
+    if (!added && id_info->kind != ID_INFO_KIND_FREE) {
+        compile_syntax_error(comp, pn, "identifier redefined as nonlocal");
         return;
     }
     id_info_t *id_info2 = scope_find_local_in_parent(comp->scope_cur, qst);
diff --git a/tests/basics/scope.py b/tests/basics/scope.py
new file mode 100644
index 0000000000..3aecc0b8d4
--- /dev/null
+++ b/tests/basics/scope.py
@@ -0,0 +1,21 @@
+# test scoping rules
+
+# explicit global variable
+a = 1
+def f():
+    global a
+    global a, a # should be able to redefine as global
+    a = 2
+f()
+print(a)
+
+# explicit nonlocal variable
+def f():
+    a = 1
+    def g():
+        nonlocal a
+        nonlocal a, a # should be able to redefine as nonlocal
+        a = 2
+    g()
+    return a
+print(f())
diff --git a/tests/basics/syntaxerror.py b/tests/basics/syntaxerror.py
index f7ccabcbb8..d6a3e3043a 100644
--- a/tests/basics/syntaxerror.py
+++ b/tests/basics/syntaxerror.py
@@ -77,8 +77,7 @@ test_syntax("return")
 test_syntax("yield")
 test_syntax("nonlocal a")
 
-# errors on uPy but shouldn't
-#test_syntax("global a; global a")
+# error on uPy, warning on CPy
 #test_syntax("def f():\n a = 1\n global a")
 
 # default except must be last
@@ -109,3 +108,12 @@ test_syntax("def f(a, a): pass")
 
 # nonlocal must exist in outer function/class scope
 test_syntax("def f():\n def g():\n  nonlocal a")
+
+# param can't be redefined as global
+test_syntax('def f(x):\n global x')
+
+# param can't be redefined as nonlocal
+test_syntax('def f(x):\n nonlocal x')
+
+# can define variable to be both nonlocal and global
+test_syntax('def f():\n nonlocal x\n global x')