REPL: Don't print the line that produced a `SyntaxWarning` if only a single line was given as input

Feature or enhancement

Bug description:

The old REPL had this behaviour:

~/dev/cpython (main)⚡ % PYTHON_BASIC_REPL=1 ./python.exe
Python 3.14.0a0 (heads/main:4606eff0aa, Jul 23 2024, 20:19:47) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> False is 0
<stdin>-0:1: SyntaxWarning: "is" with 'int' literal. Did you mean "=="?
False

The new one has this behaviour:

~/dev/cpython (main)⚡ % ./python.exe                             
Python 3.14.0a0 (heads/main:4606eff0aa, Jul 23 2024, 20:19:47) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 0 is False
<python-input-0>:1: SyntaxWarning: "is" with 'int' literal. Did you mean "=="?
  0 is False
False

The new behaviour seems better if you've given a multiline function as input since, unlike the old REPL, it tells you exactly which line of code produced the warning:

~/dev/cpython (main)⚡ % ./python.exe
Python 3.14.0a0 (heads/main:4606eff0aa, Jul 23 2024, 20:19:47) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> def foo():
...     0 is False
...     3 == 4
...     
<python-input-0>:2: SyntaxWarning: "is" with 'int' literal. Did you mean "=="?
  0 is False

...but it feels a bit redundant if, as in my first example, only a single line was entered as input. It took me a little while to figure out why the REPL was just printing the line I had typed back at me.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Beginne damit, die einzeiligen und mehrzeiligen Beispiele in der neuen CPython-REPL zu reproduzieren und ihre SyntaxWarning-Ausgabe zu vergleichen. Lies den Pfad zur Warnungsanzeige der REPL und ändere dann den einzeiligen Fall so, dass die zurückgespiegelte Quelle weggelassen wird, während die Quellzeile für mehrzeilige Eingaben erhalten bleibt; überprüfe beide Verhaltensweisen mit gezielten REPL-Tests.