Fixes#74800
The definition of `is_x86_feature_detected!` (and similar macros)
depends on the platform - it is produced by a `cfg_if!` invocation on
x86, and a plain `#[cfg]` on other platforms. Since it is part of the
prelude, we will end up importing different hygiene information
depending on the platform. This previously required us to avoid printing raw
`SyntaxContext` ids in any tests that uses the standard library, since
the captured output will be platform-dependent.
Previously, we replaced all `SyntaxContext` ids with "#CTXT", and the
raw `Span` lo/hi bytes with "LO..HI".
This commit adds `#![no_std]` and `extern crate std` to all proc-macro
tests that print spans. This suppresses the prelude import, while
still using lang items from `std` (which gives us a buildable binary).
With this apporach, we will only load hygiene information for things
which we explicitly import. This lets us re-add
`-Z unpretty=expanded,hygiene`, since its output can now be made stable
across all platforms.
Additionally, we use `-Z span-debug` in more places, which lets us avoid
the "LO..HI" normalization hack.
A raw SyntaxContext id is implicitly dependent on the target platform,
since libstd and libcore have platform-dependent #[cfg]s which affect
which macros are invoked. As a result, we must strip out any
SyntaxContext ids from test output to ensure that the captured stdout is
not platform-dependent.
The number of symbols we allocate (even early on) seems to be platform
dependent. We only care about hygiene for the purposes of this test,
so just set all of the symbol ids to zero
Normally, we encode a `Span` that references a foreign `SourceFile` by
encoding information about the foreign crate. When we decode this
`Span`, we lookup the foreign crate in order to decode the `SourceFile`.
However, this approach does not work for proc-macro crates. When we load
a proc-macro crate, we do not deserialzie any of its dependencies (since
a proc-macro crate can only export proc-macros). This means that we
cannot serialize a reference to an upstream crate, since the associated
metadata will not be available when we try to deserialize it.
This commit modifies foreign span handling so that we treat all foreign
`SourceFile`s as local `SourceFile`s when serializing a proc-macro.
All `SourceFile`s will be stored into the metadata of a proc-macro
crate, allowing us to cotinue to deserialize a proc-macro crate without
needing to load any of its dependencies.
Since the number of foreign `SourceFile`s that we load during a
compilation session may be very large, we only serialize a `SourceFile`
if we have also serialized a `Span` which requires it.
