Bytecode interpreter: Union fields are activated too eagerly

[tbaederr]

See for example: https://godbolt.org/z/453c61feh

How far up the hierarchy from a pointer we should activate is based on the syntactical structure, i.e. we need to get that information from the AST.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Timm Baeder (tbaederr)

See for example: https://godbolt.org/z/453c61feh

How far up the hierarchy from a pointer we should activate is based on the syntactical structure, i.e. we need to get that information from the AST.