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proc_macro/bridge: stop using a remote object handle for proc_macro Ident and Literal #98189

Merged
merged 5 commits into from
Jul 19, 2022
Merged

proc_macro/bridge: stop using a remote object handle for proc_macro Ident and Literal #98189

merged 5 commits into from
Jul 19, 2022

Commits on Jul 18, 2022

  1. proc_macro: use fxhash within the proc_macro crate 

    Unfortunately, as it is difficult to depend on crates from within proc_macro,
this is done by vendoring a copy of the hasher as a module rather than
depending on the rustc_hash crate.

This probably doesn't have a substantial impact up-front, however will be more
relevant once symbols are interned within the proc_macro client.
    @mystor
    mystor committed Jul 18, 2022
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  2. proc_macro: Specialize Punct::to_string 

    This was removed in a previous part, however it should be specialized for
to_string performance and consistency.
    @mystor
    mystor committed Jul 18, 2022
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  3. proc_macro: stop using a remote object handle for Ident 

    Doing this for all unicode identifiers would require a dependency on
`unicode-normalization` and `rustc_lexer`, which is currently not
possible for `proc_macro` due to it being built concurrently with `std`
and `core`. Instead, ASCII identifiers are validated locally, and an RPC
message is used to validate unicode identifiers when needed.

String values are interned on the both the server and client when
deserializing, to avoid unnecessary copies and keep Ident cheap to copy and
move. This appears to be important for performance.

The client-side interner is based roughly on the one from rustc_span, and uses
an arena inspired by rustc_arena.

RPC messages passing symbols always include the full value. This could
potentially be optimized in the future if it is revealed to be a
performance bottleneck.

Despite now having a relevant implementaion of Display for Ident, ToString is
still specialized, as it is a hot-path for this object.

The symbol infrastructure will also be used for literals in the next
part.
    @mystor
    mystor committed Jul 18, 2022
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  4. proc_macro: stop using a remote object handle for Literal 

    This builds on the symbol infrastructure built for `Ident` to replicate
the `LitKind` and `Lit` structures in rustc within the `proc_macro`
client, allowing literals to be fully created and interacted with from
the client thread. Only parsing and subspan operations still require
sync RPC.
    @mystor
    mystor committed Jul 18, 2022
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  5. proc_macro: Move subspan to be a method on Span in the bridge 

    This method is still only used for Literal::subspan, however the
implementation only depends on the Span component, so it is simpler and
more efficient for now to pass down only the information that is needed.
In the future, if more information about the Literal is required in the
implementation (e.g. to validate that spans line up as expected with
source text), that extra information can be added back with extra
arguments.
    @mystor
    mystor committed Jul 18, 2022
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