Extend the enum check to pointer and union reads

[1c3t3a]

This change extends the previously added enum discriminant check to enums read through a union or pointer. At the moment we only insert the check when transmuting to an enum. Although I hoped for it, this check isn't yet inserted for calls to MaybeUninit::assume_init, because the pass is running on polymorphic MIR and thus doesn't have the information yet to know whether the type that is read is an enum.

r? @saethlin

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[rust-log-analyzer]

The job aarch64-gnu-llvm-19-1 failed! Check out the build log: (web) (plain enhanced) (plain)

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NOTE: compiletest thinks it is using GDB version 15001000

error: gdb failed to execute
status: exit status: 1
command: PYTHONPATH="/checkout/src/etc" "/usr/bin/gdb" "-quiet" "-batch" "-nx" "-command=/checkout/obj/build/aarch64-unknown-linux-gnu/test/debuginfo/type-names.gdb/type-names.debugger.script"
--- stdout -------------------------------
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Breakpoint 1 at 0x3280: file /checkout/tests/debuginfo/type-names.rs, line 473.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".

Program received signal SIGABRT, Aborted.
0x0000fffff7ca6898 in ?? () from /lib/aarch64-linux-gnu/libc.so.6
------------------------------------------
--- stderr -------------------------------

thread 'main' panicked at /checkout/tests/debuginfo/type-names.rs:414:62:
null pointer dereference occurred