explorer crashes on the 'match ... case auto {}' construct

[pk19604014]

$ cat /tmp/crash.carbon 
package P api;

choice Ch { Alt() }

fn Main() -> i32 {
  match (Ch.Alt()) { case auto => { return 1; } }
  return 0;
}

$ bazel run --config=proto-fuzzer explorer:explorer /tmp/crash.carbon
INFO: Invocation ID: b0a75d0e-1ab7-4702-b8ae-c3ec41c5de93
INFO: Analyzed target //explorer:explorer (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
Target //explorer:explorer up-to-date:
  bazel-bin/explorer/explorer
INFO: Elapsed time: 0.110s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action
INFO: Build completed successfully, 1 total action
Please report issues to https://github.com/carbon-language/carbon-lang/issues and include the crash backtrace.
Stack dump:
0.	Program arguments: /usr/local/google/home/pk19604014/.cache/bazel/_bazel_pk19604014/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-fastbuild/bin/explorer/explorer /tmp/crash.carbon
 #0 0x00005627c3635f3b backtrace /tmp/llvm-20220302-9880-1faggz0/llvm-project-13.0.1.src/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:4202:13
 #1 0x00005627c3927ddb llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /proc/self/cwd/external/llvm-project/llvm/lib/Support/Unix/Signals.inc:565:13
 #2 0x00005627c392807b PrintStackTraceSignalHandler(void*) /proc/self/cwd/external/llvm-project/llvm/lib/Support/Unix/Signals.inc:632:1
 #3 0x00005627c3922ab8 llvm::sys::RunSignalHandlers() /proc/self/cwd/external/llvm-project/llvm/lib/Support/Signals.cpp:98:18
 #4 0x00005627c392962e SignalHandler(int) /proc/self/cwd/external/llvm-project/llvm/lib/Support/Unix/Signals.inc:407:1
 #5 0x00007f49dffe9200 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12200)
 #6 0x00005627c377286a kind /proc/self/cwd/./explorer/interpreter/value.h:97:38
 #7 0x00005627c377286a Carbon::PatternMatch(Carbon::Value const*, Carbon::Value const*, Carbon::SourceLocation, std::__1::optional<Carbon::RuntimeScope*>, std::__1::map<Carbon::GenericBinding const*, Carbon::Value const*, std::__1::less<Carbon::GenericBinding const*>, std::__1::allocator<std::__1::pair<Carbon::GenericBinding const* const, Carbon::Value const*> > >&, std::__1::optional<llvm::raw_ostream*>) /proc/self/cwd/explorer/interpreter/interpreter.cpp:217:14
 #8 0x00005627c379204d Carbon::Interpreter::StepStmt() /proc/self/cwd/explorer/interpreter/interpreter.cpp:1166:13
 #9 0x00005627c3797e77 index /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:788:12
#10 0x00005627c3797e77 index /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:1438:59
#11 0x00005627c3797e77 __holds_alternative<1UL, Carbon::Error, Carbon::Success> /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:1464:14
#12 0x00005627c3797e77 holds_alternative<Carbon::Success, Carbon::Error, Carbon::Success> /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:1470:10
#13 0x00005627c3797e77 ok /proc/self/cwd/./common/error.h:61:36
#14 0x00005627c3797e77 Carbon::Interpreter::Step() /proc/self/cwd/explorer/interpreter/interpreter.cpp:1410:7
#15 0x00005627c3798d28 Carbon::Interpreter::RunAllSteps(std::__1::unique_ptr<Carbon::Action, std::__1::default_delete<Carbon::Action> >) /proc/self/cwd/explorer/interpreter/interpreter.cpp:0:5
#16 0x00005627c3799955 ~unique_ptr /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/__memory/unique_ptr.h:272:19
#17 0x00005627c3799955 Carbon::InterpProgram(Carbon::AST const&, Carbon::Arena*, std::__1::optional<llvm::raw_ostream*>) /proc/self/cwd/explorer/interpreter/interpreter.cpp:1453:3
#18 0x00005627c36ba063 Carbon::ExecProgram(Carbon::Arena*, Carbon::AST, std::__1::optional<llvm::raw_ostream*>) /proc/self/cwd/explorer/interpreter/exec_program.cpp:0:10
#19 0x00005627c36b0215 Carbon::Main(llvm::StringRef, int, char**) /proc/self/cwd/explorer/main.cpp:78:3
#20 0x00005627c36af0dc index /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:788:12
#21 0x00005627c36af0dc index /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:1438:59
#22 0x00005627c36af0dc __holds_alternative<1UL, Carbon::Error, Carbon::Success> /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:1464:14
#23 0x00005627c36af0dc holds_alternative<Carbon::Success, Carbon::Error, Carbon::Success> /usr/local/google/home/pk19604014/.linuxbrew/Cellar/llvm/13.0.1_1/bin/../include/c++/v1/variant:1470:10
#24 0x00005627c36af0dc ok /proc/self/cwd/./common/error.h:61:36
#25 0x00005627c36af0dc Carbon::ExplorerMain(llvm::StringRef, int, char**) /proc/self/cwd/explorer/main.cpp:88:69
#26 0x00005627c36ae5a5 main /proc/self/cwd/explorer/main_bin.cpp:0:10
#27 0x00007f49dfc7d7fd __libc_start_main ./csu/../csu/libc-start.c:332:16
#28 0x00005627c35fd31a _start (/usr/local/google/home/pk19604014/.cache/bazel/_bazel_pk19604014/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-fastbuild/bin/explorer/explorer+0x3cf31a)
AddressSanitizer:DEADLYSIGNAL
=================================================================
==707017==ERROR: AddressSanitizer: SEGV on unknown address (pc 0x5627c377286a bp 0x7fff049f4520 sp 0x7fff049f4080 T0)
==707017==The signal is caused by a READ memory access.
==707017==Hint: this fault was caused by a dereference of a high value address (see register values below).  Disassemble the provided pc to learn which register was used.
    #0 0x5627c377286a in kind /proc/self/cwd/./explorer/interpreter/value.h:97:38
    #1 0x5627c377286a in Carbon::PatternMatch(Carbon::Value const*, Carbon::Value const*, Carbon::SourceLocation, std::__1::optional<Carbon::RuntimeScope*>, std::__1::map<Carbon::GenericBinding const*, Carbon::Value const*, std::__1::less<Carbon::GenericBinding const*>, std::__1::allocator<std::__1::pair<Carbon::GenericBinding const* const, Carbon::Value const*> > >&, std::__1::optional<llvm::raw_ostream*>) /proc/self/cwd/explorer/interpreter/interpreter.cpp:217:14
    #2 0x5627c379204c in Carbon::Interpreter::StepStmt() /proc/self/cwd/explorer/interpreter/interpreter.cpp:1166:13
    #3 0x5627c3797e76 in Carbon::Interpreter::Step() /proc/self/cwd/explorer/interpreter/interpreter.cpp:1410:7
    #4 0x5627c3798d27 in Carbon::Interpreter::RunAllSteps(std::__1::unique_ptr<Carbon::Action, std::__1::default_delete<Carbon::Action> >) /proc/self/cwd/explorer/interpreter/interpreter.cpp:1428:5
    #5 0x5627c3799954 in Carbon::InterpProgram(Carbon::AST const&, Carbon::Arena*, std::__1::optional<llvm::raw_ostream*>) /proc/self/cwd/explorer/interpreter/interpreter.cpp:1453:3
    #6 0x5627c36ba062 in Carbon::ExecProgram(Carbon::Arena*, Carbon::AST, std::__1::optional<llvm::raw_ostream*>) /proc/self/cwd/explorer/interpreter/exec_program.cpp:55:10
    #7 0x5627c36b0214 in Carbon::Main(llvm::StringRef, int, char**) /proc/self/cwd/explorer/main.cpp:78:3
    #8 0x5627c36af0db in Carbon::ExplorerMain(llvm::StringRef, int, char**) /proc/self/cwd/explorer/main.cpp:88:21
    #9 0x5627c36ae5a4 in main /proc/self/cwd/explorer/main_bin.cpp:29:10
    #10 0x7f49dfc7d7fc in __libc_start_main csu/../csu/libc-start.c:332:16
    #11 0x5627c35fd319 in _start (/usr/local/google/home/pk19604014/.cache/bazel/_bazel_pk19604014/0c0c6d5ac7dde4460fd40f446af91e37/execroot/carbon/bazel-out/k8-fastbuild/bin/explorer/explorer+0x3cf319)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /proc/self/cwd/./explorer/interpreter/value.h:97:38 in kind
==707017==ABORTING

[pk19604014]

Now getting this error when running on trunk:

COMPILATION ERROR: /tmp/crash.carbon:6: type error in match expression: 'choice Ch' is not implicitly convertible to 'Type'