perl cannot recover from failed class definitions (use feature "class";)

[tonycoz]

Module:

Description

Perl typically allows use to redefine anything, which allows reloading a module to recover from a failed definition, or to reload a module to simply redefine a successful definition.

The new class feature disallows both of these, but the inability to recover from the failed definition is especially a problem.

Steps to Reproduce

$ ./perl -Ilib -Mfeature=class -M-warnings=experimental -E 'eval "class C {" or print "1: $@"; eval q"class C { field $x:param; }" or print "2: $@"'
1: Missing right curly or square bracket at (eval 1) line 1, at end of line
syntax error at (eval 1) line 1, at EOF
Execution of (eval 1) aborted due to compilation errors.
2: Cannot reopen existing class "C" at (eval 2) line 1.

Expected behavior

Success when attempting to create the class with a valid definition.

Perl configuration

Summary of my perl5 (revision 5 version 39 subversion 10) configuration:
  Commit id: 122500c227656f4f9334ca280614d721dcabacba
  Platform:
    osname=linux
    osvers=6.1.0-17-amd64
    archname=x86_64-linux
    uname='linux venus 6.1.0-17-amd64 #1 smp preempt_dynamic debian 6.1.69-1 (2023-12-30) x86_64 gnulinux '
    config_args='-des -Dusedevel -DDEBUGGING -Doptimize=-O0 -g'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='cc'
    ccflags ='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O0 -g'
    cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='12.2.0'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='cc'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /usr/lib64
    libs=-lpthread -lgdbm -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
    libc=/lib/x86_64-linux-gnu/libc.so.6
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.36'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O0 -g -L/usr/local/lib -fstack-protector-strong'

Characteristics of this binary (from libperl): 
  Compile-time options:
    DEBUGGING
    HAS_LONG_DOUBLE
    HAS_STRTOLD
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_HASH_FUNC_SIPHASH13
    PERL_HASH_USE_SBOX32
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_USE_DEVEL
    PERL_USE_SAFE_PUTENV
    USE_64_BIT_ALL
    USE_64_BIT_INT
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
  Built under linux
  Compiled at Apr 24 2024 09:56:39
  %ENV:
    PERLBREW_BASHRC_VERSION="0.43"
    PERLBREW_HOME="/home/tony/.perlbrew"
    PERLBREW_MANPATH=""
    PERLBREW_PATH="/home/tony/perl5/perlbrew/bin"
    PERLBREW_ROOT="/home/tony/perl5/perlbrew"
    PERLBREW_VERSION="0.67"
  @INC:
    lib
    /usr/local/lib/perl5/site_perl/5.39.10/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.39.10
    /usr/local/lib/perl5/5.39.10/x86_64-linux
    /usr/local/lib/perl5/5.39.10

[tonycoz]

Came from discussion in #22159.