E0793: Clarify that it applies to unions as well

pick up inactive PR: rust-lang#131472

Also:
Adjust the language slightly to be more consistent with other similar messages (was created instead of got created).
Add a short section on union.
Add an example line showing referencing a field in a packed struct is safe if the field's type isn't more strictly aligned than the pack.

r? compiler-errors

Rollup of 22 pull requests

Successful merges:

 - #118087 (Add Ref/RefMut try_map method)
 - #122661 (Change the desugaring of `assert!` for better error output)
 - #140740 (Add `-Zindirect-branch-cs-prefix`)
 - #142640 (Implement autodiff using intrinsics)
 - #143075 (compiler: Allow `extern "interrupt" fn() -> !`)
 - #144865 (Fix tail calls to `#[track_caller]` functions)
 - #144944 (E0793: Clarify that it applies to unions as well)
 - #144947 (Fix description of unsigned `checked_exact_div`)
 - #145004 (Couple of minor cleanups)
 - #145005 (strip prefix of temporary file names when it exceeds filesystem name length limit)
 - #145012 (Tail call diagnostics to include lifetime info)
 - #145065 (resolve: Introduce `RibKind::Block`)
 - #145120 (llvm: Accept new LLVM lifetime format)
 - #145189 (Weekly `cargo update`)
 - #145235 (Minor `[const]` tweaks)
 - #145275 (fix(compiler/rustc_codegen_llvm): apply `target-cpu` attribute)
 - #145322 (Resolve the prelude import in `build_reduced_graph`)
 - #145331 (Make std use the edition 2024 prelude)
 - #145369 (Do not ICE on private type in field of unresolved struct)
 - #145378 (Add `FnContext` in parser for diagnostic)
 - #145389 ([rustdoc] Revert "rustdoc search: prefer stable items in search results")
 - #145392 (coverage: Remove intermediate data structures from mapping creation)

r? `@ghost`
`@rustbot` modify labels: rollup

E0793: Clarify that it applies to unions as well

pick up inactive PR: rust-lang#131472

Also:
Adjust the language slightly to be more consistent with other similar messages (was created instead of got created).
Add a short section on union.
Add an example line showing referencing a field in a packed struct is safe if the field's type isn't more strictly aligned than the pack.

r? compiler-errors

Rollup of 21 pull requests

Successful merges:

 - #118087 (Add Ref/RefMut try_map method)
 - #122661 (Change the desugaring of `assert!` for better error output)
 - #142640 (Implement autodiff using intrinsics)
 - #143075 (compiler: Allow `extern "interrupt" fn() -> !`)
 - #144865 (Fix tail calls to `#[track_caller]` functions)
 - #144944 (E0793: Clarify that it applies to unions as well)
 - #144947 (Fix description of unsigned `checked_exact_div`)
 - #145004 (Couple of minor cleanups)
 - #145005 (strip prefix of temporary file names when it exceeds filesystem name length limit)
 - #145012 (Tail call diagnostics to include lifetime info)
 - #145065 (resolve: Introduce `RibKind::Block`)
 - #145120 (llvm: Accept new LLVM lifetime format)
 - #145189 (Weekly `cargo update`)
 - #145235 (Minor `[const]` tweaks)
 - #145275 (fix(compiler/rustc_codegen_llvm): apply `target-cpu` attribute)
 - #145322 (Resolve the prelude import in `build_reduced_graph`)
 - #145331 (Make std use the edition 2024 prelude)
 - #145369 (Do not ICE on private type in field of unresolved struct)
 - #145378 (Add `FnContext` in parser for diagnostic)
 - #145389 ([rustdoc] Revert "rustdoc search: prefer stable items in search results")
 - #145392 (coverage: Remove intermediate data structures from mapping creation)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #144944 - He1pa:E0793, r=compiler-errors

E0793: Clarify that it applies to unions as well

pick up inactive PR: #131472

Also:
Adjust the language slightly to be more consistent with other similar messages (was created instead of got created).
Add a short section on union.
Add an example line showing referencing a field in a packed struct is safe if the field's type isn't more strictly aligned than the pack.

r? compiler-errors