This API is based around the unsound idea that a process can perform
checked virtual memory loads to prevent crashing. This depends on
OS-specific APIs that may be unavailable, disabled, or impossible due to
virtualization.
It also makes collecting stack traces ridiculously slow, which is a
problem for users of DebugAllocator - in other words, everybody, all the
time. It also makes strace go from being superbly clean to being awful.
The compiler actually doesn't need any functional changes for this: Sema
does reification based on the tag indices of `std.builtin.Type` already!
So, no zig1.wasm update is necessary.
This change is necessary to disallow name clashes between fields and
decls on a type, which is a prerequisite of #9938.
