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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()
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Signed-off-by: Gary Guo <gary@garyguo.net>
Currently, there is a split between `syn::Error` and pin-init's custom `DiagCtxt`. Parsing has no access to `DiagCtxt` and therefore cannot report diagnostics without failing the parse. Bridge the gap by making the `DiagCtxt` available inside parsers using `thread_local!`. `parse_macro_input!` returns error as token stream directly, so it is no longer suitable when the parsing is moved inside `DiagCtxt` closure. Add a `From<syn::Error> for ErrorGuaranteed` implementation so `?` can be used to add a `syn::Error` into the current diagnostic context and obtain a `ErrorGuaranteed`. Clean up the handler of using `<-` inside tuple expression as a demonstration of the usefulness of having `DiagCtxt` access inside `Parse`. Signed-off-by: Gary Guo <gary@garyguo.net>
Currently, if proc macro panicked, the diagnostics clean up is not executed, and further invocation will cause the "DiagCtxt cannot be nested" error. While we should aim to have no panics inside proc macros, producing a sensible diagnostics message even when macro panicked is very useful for developing. Thus, catch proc macro panics and convert them to errors, and emit them together with all diagnostics accumulated so far. Ideally we would like panic location w/ line numbers being available as well; however this is not currently implementable without overriding the global panic hook. Signed-off-by: Gary Guo <gary@garyguo.net>
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