Update README wrt. self-doc and PEP 701 f-strings

Author: netromdk

README.rst

@@ -136,38 +136,43 @@ on how to get hooks set up on your project.
 Features
 ========
 
-Features detected include v2/v3 ``print expr`` and ``print(expr)``, ``long``, f-strings, coroutines
-(``async`` and ``await``), asynchronous generators (``await`` and ``yield`` in same function),
-asynchronous comprehensions, ``await`` in comprehensions, asynchronous ``for``-loops, boolean
-constants, named expressions, keyword-only parameters, positional-only parameters, ``nonlocal``,
-``yield from``, exception context cause (``raise .. from ..``), ``except*``, ``set`` literals,
-``set`` comprehensions, ``dict`` comprehensions, infix matrix multiplication, ``"..".format(..)``,
-imports (``import X``, ``from X import Y``, ``from X import *``), function calls wrt. name and
-kwargs, ``strftime`` + ``strptime`` directives used, function and variable annotations (also
-``Final`` and ``Literal``), ``continue`` in ``finally`` block, modular inverse ``pow()``, array
-typecodes, codecs error handler names, encodings, ``%`` formatting and directives for bytes and
-bytearray, ``with`` statement, asynchronous ``with`` statement, multiple context expressions in a
-``with`` statement, multiple context expressions in a ``with`` statement grouped with parenthesis,
-unpacking assignment, generalized unpacking, ellipsis literal (``...``) out of slices, dictionary
-union (``{..}  | {..}``), dictionary union merge (``a = {..}; a |= {..}``), builtin generic type
-annotations (``list[str]``), function decorators, class decorators, relaxed decorators,
-``metaclass`` class keyword, pattern matching with ``match``, union types written as ``X | Y``, type
-alias statements (``type X = SomeType``), type alias statements with lambdas/comprehensions in class
-scopes, generic classes (``class C[T]: ...``), and template string literals (``t'{var}'``). It tries
-to detect and ignore user-defined functions, classes, arguments, and variables with names that clash
-with library-defined symbols.
+Features detected include v2/v3 ``print expr`` and ``print(expr)``, ``long``, f-strings,
+self-documenting f-strings (``f'{a=}'``), PEP 701 f-strings (same-quote nesting, multi-line
+expressions, comments/backslashes in expressions, 3.12+), coroutines (``async`` and ``await``),
+asynchronous generators (``await`` and ``yield`` in same function), asynchronous comprehensions,
+``await`` in comprehensions, asynchronous ``for``-loops, boolean constants, named expressions,
+keyword-only parameters, positional-only parameters, ``nonlocal``, ``yield from``, exception context
+cause (``raise .. from ..``), ``except*``, ``set`` literals, ``set`` comprehensions, ``dict``
+comprehensions, infix matrix multiplication, ``"..".format(..)``, imports (``import X``, ``from X
+import Y``, ``from X import *``), function calls wrt. name and kwargs, ``strftime`` + ``strptime``
+directives used, function and variable annotations (also ``Final`` and ``Literal``), ``continue`` in
+``finally`` block, modular inverse ``pow()``, array typecodes, codecs error handler names,
+encodings, ``%`` formatting and directives for bytes and bytearray, ``with`` statement, asynchronous
+``with`` statement, multiple context expressions in a ``with`` statement, multiple context
+expressions in a ``with`` statement grouped with parenthesis, unpacking assignment, generalized
+unpacking, ellipsis literal (``...``) out of slices, dictionary union (``{..}  | {..}``), dictionary
+union merge (``a = {..}; a |= {..}``), builtin generic type annotations (``list[str]``), function
+decorators, class decorators, relaxed decorators, ``metaclass`` class keyword, pattern matching with
+``match``, union types written as ``X | Y``, type alias statements (``type X = SomeType``), type
+alias statements with lambdas/comprehensions in class scopes, generic classes (``class C[T]: ...``),
+and template string literals (``t'{var}'``). It tries to detect and ignore user-defined functions,
+classes, arguments, and variables with names that clash with library-defined symbols.
 
 Caveats
 =======
 
 For frequently asked questions, check out the `FAQ discussions
 <https://github.com/netromdk/vermin/discussions/categories/faq>`__.
 
-Self-documenting fstrings detection has been disabled by default because the built-in AST cannot
-distinguish ``f'{a=}'`` from ``f'a={a}'``, for instance, since it optimizes some information away
-(`#39 <https://github.com/netromdk/vermin/issues/39>`__). And this incorrectly marks some source
-code as using fstring self-doc when only using general fstring. To enable (unstable) fstring
-self-doc detection, use ``--feature fstring-self-doc``.
+Self-documenting f-strings (``f'{a=}'``) cannot be distinguished from plain f-strings such as
+``f'a={a}'`` by the AST alone, because the parser optimizes some information away (`#39
+<https://github.com/netromdk/vermin/issues/39>`__). Vermin therefore also verifies against the
+source code, and this detection is gated behind ``--feature fstring-self-doc`` since it relies on
+heuristics that may not cover all edge cases.
+
+PEP 701 f-string features require Python 3.12+. Vermin detects these using AST analysis combined
+with source code heuristics, gated behind ``--feature fstring-pep701``, which requires Vermin to run
+on Python 3.12+ to parse the syntax (`#264 <https://github.com/netromdk/vermin/issues/264>`__).
 
 Detecting union types (``X | Y`` `PEP 604 <https://www.python.org/dev/peps/pep-0604/>`__) can be
 tricky because Vermin doesn't know all underlying details of constants and types since it parses and