https://bugs.erlang.org/browse/ERL-1026

The compiler would crash when compiling the following code:

    do(Acc) ->
        receive
            {Pid, abc} ->
                ok;
            {Pid, []} ->
                ok;
            {Pid, _Res} ->
                exit(_Res)
        end,
        do([Pid | Acc]).

The last clause that always raises an exception would confuse the
compiler so that it would think that the `receive` statement was at the
end of the function and it would generate incorrect code for the `do/1`
call following the `receive`.

https://bugs.erlang.org/browse/ERL-1022

* bjorn/compiler/fix-stack-init/ERL-1017/OTP-15968:
  Ensure that the stack slots are initialized when matching maps

When matching a map, the compiler could fail to generate code that
would initialize all stack slots (Y registers) properly. Here is a
general outline of code that *could* cause this problem:

    foo(Key, Map) ->
         Res = case Map of
                  #{Key := Val} ->
                      %% Do something with Val here.
		        .
			.
			.
                  #{} ->
		      []
              end,
	%% The stack slot for Val might not have been initialized
	%% here if the key was not present in the map.
	.
	.
	.
	%% Use Res.
	.
	.
	.

The code generator would wrongly assume that the map matching would
always initialize the stack slot, and if nothing else happened to
force that stack slot to be initialized, it would remain
uninitialized, which would likely crash the runtime system at the next
garbage collection.

`beam_validator` is supposed to find these kind of problems, but a bug
in `beam_validator` prevented it from detecting this problem.

https://bugs.erlang.org/browse/ERL-1017

* john/compiler/fix-delayed-type-inference/OTP-15954/ERL-995:
  beam_validator: Values referenced by other values must be merged

OTP-15970

* 'bjorn/compiler/length-misuse/ERL-1013' of https://github.com/bjorng/otp:
  Eliminate a crash in the type optimizer pass

OTP-15969

* 'bjorn/compiler/fix-no_type_opt/ERL-997' of https://github.com/bjorng/otp:
  Fix compiler crash when compiling with +no_type_opt

* bjorn/compiler/fix-unsafe-sharing/OTP-15963:
  Fix unsafe code sharing

If the `no_type_opt` option was given, the compiler would crash when
attempting to compile containing with a `try`...`after` construct,
such as this code:

    foo() ->
        try
            make_ref()
        after
            ok
        end.

To avoid having this bug re-appear, test the `no_type_opt` option
in the test suites.

https://bugs.erlang.org/browse/ERL-997

https://bugs.erlang.org/browse/ERL-1013