rust: pin-init: internal: handle item and expr diagnostics differently

Currently `DiagCtxt` is used to allow error recovery in the pin-init
macros, by generating both a `compile_error!()` macro item and continue
expansion, and then merge token streams together. This works very well for
items, however for expressions, this will produce invalid expression and
result in a confusing error message.

    error: macro expansion ignores `::` and any tokens following
      --> tests/ui/compile-fail/zeroable/invalid_spread.rs:15:9
       |
    13 |       let _ = init!(Foo {
       |  _____________-
    14 | |         a: 0,
    15 | |         ..MyZeroable::init_zeroed()
       | |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    16 | |     });
       | |______- caused by the macro expansion here
       |
       = note: the usage of `init!` is likely invalid in expression context

Fix this by wrap the concatenated diagnostics in a block, with the
generated expression in its tail position. This results in the desired
error message.

    error: expected nothing or `..Zeroable::init_zeroed()`.
      --> tests/ui/compile-fail/zeroable/invalid_spread.rs:15:9
       |
    15 |         ..MyZeroable::init_zeroed()
       |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^

Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://patch.msgid.link/20260923140618.1978181-1-gary@kernel.org
Signed-off-by: Gary Guo <gary@garyguo.net>

0 files changed, 0 insertions, 0 deletions