in dict displays, evaluate the key before the value (closes #11205)

Patch partially by Steve Dougherty.

Lib/importlib/_bootstrap_external.py

@@ -221,12 +221,13 @@ _code_type = type(_write_atomic.__code__)
 #     Python 3.4rc2 3310 (alter __qualname__ computation)
 #     Python 3.5a0  3320 (matrix multiplication operator)
 #     Python 3.5b1  3330 (PEP 448: Additional Unpacking Generalizations)
+#     Python 3.5b2  3340 (fix dictionary display evaluation order #11205)
 #
 # MAGIC must change whenever the bytecode emitted by the compiler may no
 # longer be understood by older implementations of the eval loop (usually
 # due to the addition of new opcodes).
 
-MAGIC_NUMBER = (3330).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3340).to_bytes(2, 'little') + b'\r\n'
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'

Lib/test/test_compile.py

@@ -461,6 +461,17 @@ if 1:
         ast.body = [_ast.BoolOp()]
         self.assertRaises(TypeError, compile, ast, '<ast>', 'exec')
 
+    def test_dict_evaluation_order(self):
+        i = 0
+
+        def f():
+            nonlocal i
+            i += 1
+            return i
+
+        d = {f(): f(), f(): f()}
+        self.assertEqual(d, {1: 2, 3: 4})
+
     @support.cpython_only
     def test_same_filename_used(self):
         s = """def f(): pass\ndef g(): pass"""

Misc/NEWS

@@ -10,6 +10,8 @@ Release date: 2015-07-05
 Core and Builtins
 -----------------
 
+- Issue #11205: In dictionary displays, evaluate the key before the value.
+
 - Issue #24285: Fixed regression that prevented importing extension modules
   from inside packages. Patch by Petr Viktorin.
 

Python/ceval.c

@@ -2584,8 +2584,8 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
                 goto error;
             while (--oparg >= 0) {
                 int err;
-                PyObject *key = TOP();
-                PyObject *value = SECOND();
+                PyObject *value = TOP();
+                PyObject *key = SECOND();
                 STACKADJ(-2);
                 err = PyDict_SetItem(map, key, value);
                 Py_DECREF(value);

Python/compile.c

@@ -3138,8 +3138,8 @@ compiler_dict(struct compiler *c, expr_ty e)
             containers++;
         }
         else {
-            VISIT(c, expr, (expr_ty)asdl_seq_GET(e->v.Dict.values, i));
             VISIT(c, expr, (expr_ty)asdl_seq_GET(e->v.Dict.keys, i));
+            VISIT(c, expr, (expr_ty)asdl_seq_GET(e->v.Dict.values, i));
             elements++;
         }
     }
@@ -3287,8 +3287,8 @@ compiler_call_helper(struct compiler *c,
         }
         else if (nsubkwargs) {
             /* A keyword argument and we already have a dict. */
-            VISIT(c, expr, kw->value);
             ADDOP_O(c, LOAD_CONST, kw->arg, consts);
+            VISIT(c, expr, kw->value);
             nseen++;
         }
         else {