Incorrect error message for `yield from`

[JelleZijlstra]

Bug report

Bug description:

% ./python.exe -c 'yield x'
  File "<string>", line 1
SyntaxError: 'yield' outside function
% ./python.exe -c 'yield from x'
  File "<string>", line 1
SyntaxError: 'yield' outside function
% ./python.exe -c 'async def f(): yield from x'
  File "<string>", line 1
SyntaxError: 'yield from' inside async function

The middle one should also say "yield from".

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-121657: Display correct error message for yield from outside of a … #121680
• gh-121657: Added an additional test using lambda #121722
• [3.13] gh-121657: Display correct error message for yield from outsid… #121768
• [3.12] gh-121657: Display correct error message for yield from outsid… #121769
• [3.13] gh-121657: Additional yield from error test using lambda (GH-121722) #121961
• [3.12] gh-121657: Additional yield from error test using lambda (GH-121722) #121962

[JelleZijlstra]

This is very easy to fix but I'll leave it for a bit in case a new contributor wants to get familiar with making a CPython change. Pointers for the fix:

• The code to be changed is in compile.c, currently at line 6122 (search for "'yield' outside function" if it changes).
• Tests should be added, probably around here Lib/test/test_generators.py:SyntaxError: 'yield' outside function. The existing test only tests yield, not yield from; we should add more tests.

[serhiy-storchaka]

I am not sure 5his should be fixed, as technically the error message is correct.

The error message in the third example is more specific because yield is valid here.

[gege-hoho]

I will give it a try :)

[encukou]

The existing message was technically correct, but yield from is definitely better.