[Perl/perl5] 2bb889: add OPpCONST_TOKEN_* flags to aid deparsing

[iabyn via perl5-changes]

Branch: refs/heads/blead
Home: https://github.com/Perl/perl5
Commit: 2bb889fc6c12b192e0fcde37af5e638d5cb8e181
https://github.com/Perl/perl5/commit/2bb889fc6c12b192e0fcde37af5e638d5cb8e181
Author: David Mitchell <da...@iabyn.com>
Date: 2024-02-22 (Thu, 22 Feb 2024)

Changed paths:
M Porting/deparse-skips.txt
M lib/B/Deparse.pm
M lib/B/Deparse.t
M lib/B/Op_private.pm
M opcode.h
M regen/op_private
M toke.c

Log Message:
-----------
add OPpCONST_TOKEN_* flags to aid deparsing

Code like

my $line = __LINE__;
my $file = __FILE__;
my $pkg = __PACKAGE__;

was being deparsed as

my $line = '42';
my $file = 'foo.pl';
my $pkg = 'Foo::Bar';

because __LINE__ etc are converted by the lexer into an ordinary
OP_CONST, whose SV is just a plain string holding the line number or
whatever.

This commit uses two spare bits in op_private on OP_CONST ops to create
a 4-valued bit field, indicating whether the op is a normal constant or
one of those three special constant tokens. This field is then used
by Deparse to output a literal "__LINE__" or whatever rather than the
value of the constant.

This fixes one failing test file under
cd t; ./TEST -deparse
and removes one (but not all) sources of failure from three others.

Note that __SUB__ is already special-cased to deparse literally
(except when used outside a sub where it deparses as 'undef'), while
the special tokens __DATA__, __END__ and __CLASS__ don't generate
OP_CONSTs.



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