bpo-43797: Handle correctly invalid assignments inside function calls and generators (GH-25390)

Grammar/python.gram

@@ -638,7 +638,7 @@ group[expr_ty]:
     | '(' a=(yield_expr | named_expression) ')' { a }
     | invalid_group
 genexp[expr_ty]:
-    | '(' a=named_expression b=for_if_clauses ')' { _PyAST_GeneratorExp(a, b, EXTRA) }
+    | '(' a=direct_named_expression b=for_if_clauses ')' { _PyAST_GeneratorExp(a, b, EXTRA) }
     | invalid_comprehension
 set[expr_ty]: '{' a=star_named_expressions '}' { _PyAST_Set(a, EXTRA) }
 setcomp[expr_ty]:

Lib/test/test_genexps.py

@@ -103,7 +103,7 @@ Verify that parenthesis are required when used as a keyword argument value
     >>> dict(a = i for i in range(10))
     Traceback (most recent call last):
        ...
-    SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?
+    SyntaxError: invalid syntax
 
 Verify that parenthesis are required when used as a keyword argument value
 

Lib/test/test_syntax.py

@@ -868,6 +868,18 @@ Ensure that early = are not matched by the parser as invalid comparisons
    Traceback (most recent call last):
    SyntaxError: invalid syntax
 
+   >>> dict(x=34); x $ y
+   Traceback (most recent call last):
+   SyntaxError: invalid syntax
+
+   >>> dict(x=34, (x for x in range 10), 1); x $ y
+   Traceback (most recent call last):
+   SyntaxError: invalid syntax
+
+   >>> dict(x=34, x=1, y=2); x $ y
+   Traceback (most recent call last):
+   SyntaxError: invalid syntax
+
 Make sure that the old "raise X, Y[, Z]" form is gone:
    >>> raise X, Y
    Traceback (most recent call last):
@@ -1013,7 +1025,7 @@ class SyntaxTestCase(unittest.TestCase):
     def test_expression_with_assignment(self):
         self._check_error(
             "print(end1 + end2 = ' ')",
-            "cannot assign to expression here. Maybe you meant '==' instead of '='?",
+            'expression cannot contain assignment, perhaps you meant "=="?',
             offset=19
         )
 

Parser/parser.c

@@ -14015,7 +14015,7 @@ group_rule(Parser *p)
     return _res;
 }
 
-// genexp: '(' named_expression for_if_clauses ')' | invalid_comprehension
+// genexp: '(' direct_named_expression for_if_clauses ')' | invalid_comprehension
 static expr_ty
 genexp_rule(Parser *p)
 {
@@ -14035,12 +14035,12 @@ genexp_rule(Parser *p)
     UNUSED(_start_lineno); // Only used by EXTRA macro
     int _start_col_offset = p->tokens[_mark]->col_offset;
     UNUSED(_start_col_offset); // Only used by EXTRA macro
-    { // '(' named_expression for_if_clauses ')'
+    { // '(' direct_named_expression for_if_clauses ')'
         if (p->error_indicator) {
             D(p->level--);
             return NULL;
         }
-        D(fprintf(stderr, "%*c> genexp[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "'(' named_expression for_if_clauses ')'"));
+        D(fprintf(stderr, "%*c> genexp[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "'(' direct_named_expression for_if_clauses ')'"));
         Token * _literal;
         Token * _literal_1;
         expr_ty a;
@@ -14048,14 +14048,14 @@ genexp_rule(Parser *p)
         if (
             (_literal = _PyPegen_expect_token(p, 7))  // token='('
             &&
-            (a = named_expression_rule(p))  // named_expression
+            (a = direct_named_expression_rule(p))  // direct_named_expression
             &&
             (b = for_if_clauses_rule(p))  // for_if_clauses
             &&
             (_literal_1 = _PyPegen_expect_token(p, 8))  // token=')'
         )
         {
-            D(fprintf(stderr, "%*c+ genexp[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "'(' named_expression for_if_clauses ')'"));
+            D(fprintf(stderr, "%*c+ genexp[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "'(' direct_named_expression for_if_clauses ')'"));
             Token *_token = _PyPegen_get_last_nonnwhitespace_token(p);
             if (_token == NULL) {
                 D(p->level--);
@@ -14075,7 +14075,7 @@ genexp_rule(Parser *p)
         }
         p->mark = _mark;
         D(fprintf(stderr, "%*c%s genexp[%d-%d]: %s failed!\n", p->level, ' ',
-                  p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'(' named_expression for_if_clauses ')'"));
+                  p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "'(' direct_named_expression for_if_clauses ')'"));
     }
     if (p->call_invalid_rules) { // invalid_comprehension
         if (p->error_indicator) {