compiler now ignores constant statements

The compile ignores constant statements and emit a SyntaxWarning warning.

Don't emit the warning for string statement because triple quoted string is a
common syntax for multiline comments.

Don't emit the warning on ellipis neither: 'def f(): ...' is a legit syntax for
abstract functions.

Changes:

* test_ast: ignore SyntaxWarning when compiling test statements. Modify
  test_load_const() to use assignment expressions rather than constant
  expression.
* test_code: add more kinds of constant statements, ignore SyntaxWarning when
  testing that the compiler removes constant statements.
* test_grammar: ignore SyntaxWarning on the statement "1"

1 files changed, 30 insertions, 11 deletions

diff --git a/Python/compile.c b/Python/compile.c
index ccb05cf..84b79a2 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -2616,20 +2616,39 @@ compiler_visit_stmt_expr(struct compiler *c, expr_ty value)
         return 1;
     }
 
-    if (value->kind == Str_kind || value->kind == Num_kind) {
-        /* ignore strings and numbers */
+    switch (value->kind)
+    {
+    case Str_kind:
+    case Ellipsis_kind:
+        /* Issue #26204: ignore string statement, but don't emit a
+         * SyntaxWarning. Triple quoted strings is a common syntax for
+         * multiline comments.
+         *
+         * Don't emit warning on "def f(): ..." neither. It's a legit syntax
+         * for abstract function. */
         return 1;
-    }
 
-    if (value->kind == Constant_kind) {
-        PyObject *cst = value->v.Constant.value;
-        if (PyUnicode_CheckExact(cst)
-            || PyLong_CheckExact(cst)
-            || PyFloat_CheckExact(cst)
-            || PyComplex_CheckExact(cst)) {
-            /* ignore strings and numbers */
-            return 1;
+    case Bytes_kind:
+    case Num_kind:
+    case NameConstant_kind:
+    case Constant_kind:
+    {
+        PyObject *msg = PyUnicode_FromString("ignore constant statement");
+        if (msg == NULL)
+            return 0;
+        if (PyErr_WarnExplicitObject(PyExc_SyntaxWarning,
+                                     msg,
+                                     c->c_filename, c->u->u_lineno,
+                                     NULL, NULL) == -1) {
+            Py_DECREF(msg);
+            return 0;
         }
+        Py_DECREF(msg);
+        return 1;
+    }
+
+    default:
+        break;
     }
 
     VISIT(c, expr, value);