f916b0474a
This PR implements span quoting, allowing proc-macros to produce spans
pointing *into their own crate*. This is used by the unstable
`proc_macro::quote!` macro, allowing us to get error messages like this:
```
error[E0412]: cannot find type `MissingType` in this scope
--> $DIR/auxiliary/span-from-proc-macro.rs:37:20
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LL | pub fn error_from_attribute(_args: TokenStream, _input: TokenStream) -> TokenStream {
| ----------------------------------------------------------------------------------- in this expansion of procedural macro `#[error_from_attribute]`
...
LL | field: MissingType
| ^^^^^^^^^^^ not found in this scope
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::: $DIR/span-from-proc-macro.rs:8:1
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LL | #[error_from_attribute]
| ----------------------- in this macro invocation
```
Here, `MissingType` occurs inside the implementation of the proc-macro
`#[error_from_attribute]`. Previosuly, this would always result in a
span pointing at `#[error_from_attribute]`
This will make many proc-macro-related error message much more useful -
when a proc-macro generates code containing an error, users will get an
error message pointing directly at that code (within the macro
definition), instead of always getting a span pointing at the macro
invocation site.
This is implemented as follows:
* When a proc-macro crate is being *compiled*, it causes the `quote!`
macro to get run. This saves all of the sapns in the input to `quote!`
into the metadata of *the proc-macro-crate* (which we are currently
compiling). The `quote!` macro then expands to a call to
`proc_macro::Span::recover_proc_macro_span(id)`, where `id` is an
opaque identifier for the span in the crate metadata.
* When the same proc-macro crate is *run* (e.g. it is loaded from disk
and invoked by some consumer crate), the call to
`proc_macro::Span::recover_proc_macro_span` causes us to load the span
from the proc-macro crate's metadata. The proc-macro then produces a
`TokenStream` containing a `Span` pointing into the proc-macro crate
itself.
The recursive nature of 'quote!' can be difficult to understand at
first. The file `src/test/ui/proc-macro/quote-debug.stdout` shows
the output of the `quote!` macro, which should make this eaier to
understand.
This PR also supports custom quoting spans in custom quote macros (e.g.
the `quote` crate). All span quoting goes through the
`proc_macro::quote_span` method, which can be called by a custom quote
macro to perform span quoting. An example of this usage is provided in
`src/test/ui/proc-macro/auxiliary/custom-quote.rs`
Custom quoting currently has a few limitations:
In order to quote a span, we need to generate a call to
`proc_macro::Span::recover_proc_macro_span`. However, proc-macros
support renaming the `proc_macro` crate, so we can't simply hardcode
this path. Previously, the `quote_span` method used the path
`crate::Span` - however, this only works when it is called by the
builtin `quote!` macro in the same crate. To support being called from
arbitrary crates, we need access to the name of the `proc_macro` crate
to generate a path. This PR adds an additional argument to `quote_span`
to specify the name of the `proc_macro` crate. Howver, this feels kind
of hacky, and we may want to change this before stabilizing anything
quote-related.
Additionally, using `quote_span` currently requires enabling the
`proc_macro_internals` feature. The builtin `quote!` macro
has an `#[allow_internal_unstable]` attribute, but this won't work for
custom quote implementations. This will likely require some additional
tricks to apply `allow_internal_unstable` to the span of
`proc_macro::Span::recover_proc_macro_span`.
122 lines
4 KiB
Rust
122 lines
4 KiB
Rust
//! This crate contains implementations of built-in macros and other code generating facilities
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//! injecting code into the crate before it is lowered to HIR.
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#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
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#![feature(box_patterns)]
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#![feature(box_syntax)]
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#![feature(bool_to_option)]
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#![feature(crate_visibility_modifier)]
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#![feature(decl_macro)]
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#![feature(iter_zip)]
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#![feature(nll)]
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#![cfg_attr(bootstrap, feature(or_patterns))]
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#![feature(proc_macro_internals)]
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#![feature(proc_macro_quote)]
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#![recursion_limit = "256"]
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extern crate proc_macro;
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use crate::deriving::*;
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use rustc_expand::base::{MacroExpanderFn, ResolverExpand, SyntaxExtensionKind};
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use rustc_expand::proc_macro::BangProcMacro;
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use rustc_span::def_id::LOCAL_CRATE;
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use rustc_span::symbol::sym;
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mod asm;
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mod assert;
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mod cfg;
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mod cfg_accessible;
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mod cfg_eval;
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mod compile_error;
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mod concat;
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mod concat_idents;
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mod derive;
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mod deriving;
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mod env;
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mod format;
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mod format_foreign;
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mod global_allocator;
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mod global_asm;
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mod llvm_asm;
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mod log_syntax;
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mod panic;
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mod source_util;
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mod test;
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mod trace_macros;
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mod util;
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pub mod cmdline_attrs;
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pub mod proc_macro_harness;
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pub mod standard_library_imports;
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pub mod test_harness;
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pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
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let mut register = |name, kind| resolver.register_builtin_macro(name, kind);
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macro register_bang($($name:ident: $f:expr,)*) {
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$(register(sym::$name, SyntaxExtensionKind::LegacyBang(Box::new($f as MacroExpanderFn)));)*
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}
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macro register_attr($($name:ident: $f:expr,)*) {
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$(register(sym::$name, SyntaxExtensionKind::LegacyAttr(Box::new($f)));)*
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}
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macro register_derive($($name:ident: $f:expr,)*) {
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$(register(sym::$name, SyntaxExtensionKind::LegacyDerive(Box::new(BuiltinDerive($f))));)*
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}
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register_bang! {
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asm: asm::expand_asm,
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assert: assert::expand_assert,
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cfg: cfg::expand_cfg,
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column: source_util::expand_column,
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compile_error: compile_error::expand_compile_error,
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concat_idents: concat_idents::expand_concat_idents,
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concat: concat::expand_concat,
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env: env::expand_env,
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file: source_util::expand_file,
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format_args_nl: format::expand_format_args_nl,
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format_args: format::expand_format_args,
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global_asm: global_asm::expand_global_asm,
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include_bytes: source_util::expand_include_bytes,
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include_str: source_util::expand_include_str,
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include: source_util::expand_include,
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line: source_util::expand_line,
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llvm_asm: llvm_asm::expand_llvm_asm,
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log_syntax: log_syntax::expand_log_syntax,
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module_path: source_util::expand_mod,
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option_env: env::expand_option_env,
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core_panic: panic::expand_panic,
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std_panic: panic::expand_panic,
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stringify: source_util::expand_stringify,
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trace_macros: trace_macros::expand_trace_macros,
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}
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register_attr! {
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bench: test::expand_bench,
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cfg_accessible: cfg_accessible::Expander,
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cfg_eval: cfg_eval::expand,
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derive: derive::Expander,
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global_allocator: global_allocator::expand,
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test: test::expand_test,
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test_case: test::expand_test_case,
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}
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register_derive! {
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Clone: clone::expand_deriving_clone,
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Copy: bounds::expand_deriving_copy,
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Debug: debug::expand_deriving_debug,
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Default: default::expand_deriving_default,
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Eq: eq::expand_deriving_eq,
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Hash: hash::expand_deriving_hash,
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Ord: ord::expand_deriving_ord,
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PartialEq: partial_eq::expand_deriving_partial_eq,
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PartialOrd: partial_ord::expand_deriving_partial_ord,
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RustcDecodable: decodable::expand_deriving_rustc_decodable,
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RustcEncodable: encodable::expand_deriving_rustc_encodable,
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}
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let client = proc_macro::bridge::client::Client::expand1(proc_macro::quote);
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register(
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sym::quote,
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SyntaxExtensionKind::Bang(Box::new(BangProcMacro { client, krate: LOCAL_CRATE })),
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);
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}
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