bpo-34013: Generalize the invalid legacy statement error message (GH-27389)

Author: pablogsal

Grammar/python.gram

@@ -847,10 +847,15 @@ expression_without_invalid[expr_ty]:
     | a=disjunction 'if' b=disjunction 'else' c=expression { _PyAST_IfExp(b, a, c, EXTRA) }
     | disjunction
     | lambdef
+invalid_legacy_expression:
+    | a=NAME b=expression_without_invalid {
+        _PyPegen_check_legacy_stmt(p, a) ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "Missing parentheses in call to '%U'.", a->v.Name.id) : NULL}
+ 
 invalid_expression:
+   | invalid_legacy_expression
     # !(NAME STRING) is not matched so we don't show this error with some invalid string prefixes like: kf"dsfsdf"
     # Soft keywords need to also be ignored because they can be parsed as NAME NAME
-    | !(NAME STRING | SOFT_KEYWORD) a=disjunction b=expression_without_invalid {
+   | !(NAME STRING | SOFT_KEYWORD) a=disjunction b=expression_without_invalid {
         RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax. Perhaps you forgot a comma?") }
 
 invalid_named_expression:

Lib/test/test_exceptions.py

@@ -175,9 +175,15 @@ def ckmsg(src, msg, exception=SyntaxError):
         ckmsg(s, "Missing parentheses in call to 'print'. "
                  "Did you mean print(\"old style\", end=\" \")?")
 
+        s = 'print f(a+b,c)'
+        ckmsg(s, "Missing parentheses in call to 'print'.")
+
         s = '''exec "old style"'''
         ckmsg(s, "Missing parentheses in call to 'exec'")
 
+        s = 'exec f(a+b,c)'
+        ckmsg(s, "Missing parentheses in call to 'exec'.")
+
         # should not apply to subclasses, see issue #31161
         s = '''if True:\nprint "No indent"'''
         ckmsg(s, "expected an indented block after 'if' statement on line 1", IndentationError)

Misc/NEWS.d/next/Core and Builtins/2021-07-27-11-14-22.bpo-34013.SjLFe-.rst

@@ -0,0 +1,3 @@
+Generalize the invalid legacy statement custom error message (like the one
+generated when "print" is called without parentheses) to include more
+generic expressions. Patch by Pablo Galindo