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//! This crate contains implementations of built-in macros and other code generating facilities
//! 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)]
#![feature(box_syntax)]
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#![feature(bool_to_option)]
#![feature(crate_visibility_modifier)]
#![feature(decl_macro)]
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#![feature(iter_zip)]
#![feature(nll)]
#![feature(proc_macro_internals)]
#![feature(proc_macro_quote)]
#![recursion_limit = "256"]
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extern crate proc_macro;
use crate::deriving::*;
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use rustc_expand::base::{MacroExpanderFn, ResolverExpand, SyntaxExtensionKind};
use rustc_expand::proc_macro::BangProcMacro;
Implement span quoting for proc-macros 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 | 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 | ::: $DIR/span-from-proc-macro.rs:8:1 | 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`.
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use rustc_span::def_id::LOCAL_CRATE;
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use rustc_span::symbol::sym;
mod asm;
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mod assert;
mod cfg;
mod cfg_accessible;
mod cfg_eval;
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mod compile_error;
mod concat;
mod concat_idents;
mod derive;
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mod deriving;
mod env;
mod format;
mod format_foreign;
mod global_allocator;
mod llvm_asm;
mod log_syntax;
mod panic;
mod source_util;
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mod test;
mod trace_macros;
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mod util;
pub mod cmdline_attrs;
pub mod proc_macro_harness;
pub mod standard_library_imports;
pub mod test_harness;
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pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
let mut register = |name, kind| resolver.register_builtin_macro(name, kind);
macro register_bang($($name:ident: $f:expr,)*) {
$(register(sym::$name, SyntaxExtensionKind::LegacyBang(Box::new($f as MacroExpanderFn)));)*
}
macro register_attr($($name:ident: $f:expr,)*) {
$(register(sym::$name, SyntaxExtensionKind::LegacyAttr(Box::new($f)));)*
}
macro register_derive($($name:ident: $f:expr,)*) {
$(register(sym::$name, SyntaxExtensionKind::LegacyDerive(Box::new(BuiltinDerive($f))));)*
}
register_bang! {
asm: asm::expand_asm,
assert: assert::expand_assert,
cfg: cfg::expand_cfg,
column: source_util::expand_column,
compile_error: compile_error::expand_compile_error,
concat_idents: concat_idents::expand_concat_idents,
concat: concat::expand_concat,
env: env::expand_env,
file: source_util::expand_file,
format_args_nl: format::expand_format_args_nl,
format_args: format::expand_format_args,
global_asm: asm::expand_global_asm,
include_bytes: source_util::expand_include_bytes,
include_str: source_util::expand_include_str,
include: source_util::expand_include,
line: source_util::expand_line,
llvm_asm: llvm_asm::expand_llvm_asm,
log_syntax: log_syntax::expand_log_syntax,
module_path: source_util::expand_mod,
option_env: env::expand_option_env,
core_panic: panic::expand_panic,
std_panic: panic::expand_panic,
stringify: source_util::expand_stringify,
trace_macros: trace_macros::expand_trace_macros,
}
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register_attr! {
bench: test::expand_bench,
cfg_accessible: cfg_accessible::Expander,
cfg_eval: cfg_eval::expand,
derive: derive::Expander,
global_allocator: global_allocator::expand,
test: test::expand_test,
test_case: test::expand_test_case,
}
register_derive! {
Clone: clone::expand_deriving_clone,
Copy: bounds::expand_deriving_copy,
Debug: debug::expand_deriving_debug,
Default: default::expand_deriving_default,
Eq: eq::expand_deriving_eq,
Hash: hash::expand_deriving_hash,
Ord: ord::expand_deriving_ord,
PartialEq: partial_eq::expand_deriving_partial_eq,
PartialOrd: partial_ord::expand_deriving_partial_ord,
RustcDecodable: decodable::expand_deriving_rustc_decodable,
RustcEncodable: encodable::expand_deriving_rustc_encodable,
}
let client = proc_macro::bridge::client::Client::expand1(proc_macro::quote);
Implement span quoting for proc-macros 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 | 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 | ::: $DIR/span-from-proc-macro.rs:8:1 | 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`.
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register(
sym::quote,
SyntaxExtensionKind::Bang(Box::new(BangProcMacro { client, krate: LOCAL_CRATE })),
);
}