Revert r82044, since it changed the semantics of negated imaginary literals.

mdickinson · mdickinson · commit ce5b6c43bfbd · 2010-06-30T10:34:53.000Z
Before r82044, '-7j' became complex(0.0, -7.0);  afterwards it was
complex(-0.0, -7.0).  See issue 9011.
diff --git a/Lib/test/test_parser.py b/Lib/test/test_parser.py
@@ -479,16 +479,6 @@ def test_compile_badunicode(self):
         st = parser.suite('a = "\\u1"')
         self.assertRaises(SyntaxError, parser.compilest, st)
 
-    def test_issue_9011(self):
-        # Issue 9011: compilation of an unary minus expression changed
-        # the meaning of the ST, so that a second compilation produced
-        # incorrect results.
-        st = parser.expr('-3')
-        code1 = parser.compilest(st)
-        self.assertEqual(eval(code1), -3)
-        code2 = parser.compilest(st)
-        self.assertEqual(eval(code2), -3)
-
 class ParserStackLimitTestCase(unittest.TestCase):
     """try to push the parser to/over its limits.
     see http://bugs.python.org/issue1881 for a discussion
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -16,11 +16,6 @@ Core and Builtins
   Fix the encoding of the modules filename. Patch written by Amaury Forgeot
   d'Arc.
 
-- Issue #9011: Remove buggy and unnecessary (in 3.x) ST->AST
-  compilation code dealing with unary minus applied to a constant.
-  The removed code was mutating the ST, causing a second compilation
-  to fail.
-
 - Issue #9058: Remove assertions about INT_MAX in UnicodeDecodeError.
 
 - Issue #8941: decoding big endian UTF-32 data in UCS-2 builds could crash
diff --git a/Python/ast.c b/Python/ast.c
@@ -1664,8 +1664,34 @@ ast_for_trailer(struct compiling *c, const node *n, expr_ty left_expr)
 static expr_ty
 ast_for_factor(struct compiling *c, const node *n)
 {
+    node *pfactor, *ppower, *patom, *pnum;
     expr_ty expression;
 
+    /* If the unary - operator is applied to a constant, don't generate
+       a UNARY_NEGATIVE opcode.  Just store the approriate value as a
+       constant.  The peephole optimizer already does something like
+       this but it doesn't handle the case where the constant is
+       (sys.maxint - 1).  In that case, we want a PyIntObject, not a
+       PyLongObject.
+    */
+    if (TYPE(CHILD(n, 0)) == MINUS
+        && NCH(n) == 2
+        && TYPE((pfactor = CHILD(n, 1))) == factor
+        && NCH(pfactor) == 1
+        && TYPE((ppower = CHILD(pfactor, 0))) == power
+        && NCH(ppower) == 1
+        && TYPE((patom = CHILD(ppower, 0))) == atom
+        && TYPE((pnum = CHILD(patom, 0))) == NUMBER) {
+        char *s = PyObject_MALLOC(strlen(STR(pnum)) + 2);
+        if (s == NULL)
+            return NULL;
+        s[0] = '-';
+        strcpy(s + 1, STR(pnum));
+        PyObject_FREE(STR(pnum));
+        STR(pnum) = s;
+        return ast_for_atom(c, patom);
+    }
+
     expression = ast_for_expr(c, CHILD(n, 1));
     if (!expression)
         return NULL;
