Package: cc-mode;
Reported by: Arsen Arsenović <arsen <at> aarsen.me>
Date: Sun, 18 Aug 2024 09:52:02 UTC
Severity: normal
Done: Alan Mackenzie <acm <at> muc.de>
Bug is archived. No further changes may be made.
View this message in rfc822 format
From: Arsen Arsenović <arsen <at> aarsen.me> To: 72695 <at> debbugs.gnu.org Subject: bug#72695: CC Mode 5.35.2 (C++//l); c++-mode misindents 'if constexpr' inside lambdas Date: Sun, 18 Aug 2024 11:50:32 +0200
Package: cc-mode
<#secure method=pgpmime mode=sign>
Package: cc-mode
Hi!
CC-mode appears to misindent the following C++ snippet:
void f()
{
auto data_printer = [] <typename T>
(const T& data)
{
if constexpr (true)
{
if constexpr (std::same_as<T, std::string>)
std::println (" data: \"{}\"", data);
else
std::println (" data: {}", data);
}
else
std::println ("");
};
if constexpr (false)
{
foo ();
}
}
This example is supposed to be formatted in accordance to the default
GNU style, but the 'if constexpr' in the lambda expression are
misindented.
This might be the case because the inline-open of the lambda gets
mis-interpreted as statement-cont, so the statements in the body are
indented as brace-list-intro and brace-entry-open rather than
statement-block-intro and substatement-open.
WRT lambda indentation generally, CC-mode appears to format lambdas in
GNU style so that their '{' aligns with their '[' (i.e. aligns their
compound-statement with their lambda-introducer per ISO parlance).
Maybe we should consider indenting them less. For instance, that
indentation leads to:
std::visit ([] <typename T>
(const T& data)
{
if constexpr (!std::same_as<T, std::monostate>)
{
if constexpr (std::same_as<T, std::string>)
std::println (" data: \"{}\"", data);
else
std::println (" data: {}", data);
}
else
std::println ("");
}, tok.data);
... which is /really/ aggressive. Maybe it'd be better to do something
like:
std::visit ([]
(args)
{
body
},
visit-args-cont);
I realize this is a bit inconsistent with the rest of the style, but
given that placing the introducer (and generally function arguments) on
a new line does not work in the GNU C/++ style as it does in Lisp:
function_name (
arg1,
arg2);
... versus:
(function-name
arg1
arg2)
Anyway, thanks in advance!
Have a most lovely day.
Emacs : GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.42, cairo version 1.18.0)
of 2024-08-13
Package: CC Mode 5.35.2 (C++//l)
Buffer Style: gnu
c-emacs-features: (pps-extended-state col-0-paren posix-char-classes gen-string-delim gen-comment-delim syntax-properties category-properties 1-bit)
current state:
==============
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c-cleanup-list '(scope-operator)
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(c . c-lineup-C-comments)
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c-lineup-gnu-DEFUN-intro-cont)
(brace-list-intro first c-lineup-2nd-brace-entry-in-arglist
c-lineup-class-decl-init-+ +)
(brace-list-open . +)
(inline-open . 0)
(arglist-close . c-lineup-arglist)
(arglist-intro . c-lineup-arglist-intro-after-paren)
(statement-cont . +)
(statement-case-open . +)
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(knr-argdecl-intro . 5)
(statement-block-intro . +)
)
c-buffer-is-cc-mode 'c++-mode
c-tab-always-indent t
c-syntactic-indentation t
c-syntactic-indentation-in-macros t
c-ignore-auto-fill '(string cpp code)
c-auto-align-backslashes t
c-backspace-function 'backward-delete-char-untabify
c-delete-function 'delete-char
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c-default-style '((java-mode . "java") (awk-mode . "awk") (other . "gnu"))
c-enable-xemacs-performance-kludge-p nil
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defun-prompt-regexp nil
tab-width 8
comment-column 32
parse-sexp-ignore-comments t
parse-sexp-lookup-properties t
auto-fill-function 'c-do-auto-fill
comment-multi-line t
comment-start-skip "\\(?://+\\|/\\*+\\)\\s *"
fill-prefix nil
fill-column 79
paragraph-start "[ ]*\\(//+\\|\\**\\)[ ]*$\\|^\f"
adaptive-fill-mode t
adaptive-fill-regexp "[ ]*\\(//+\\|\\**\\)[ ]*\\([-–!|#%;>*·•‣⁃◦ ]*\\)"
)
--
Arsen Arsenović
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.