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[experiment] expand: Make #[derive(A, B, ...)] cfg-eval its input only for A, B, ... #86057

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[experiment] expand: Make #[derive(A, B, ...)] cfg-eval its input only for A, B, ... #86057

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24 changes: 11 additions & 13 deletions compiler/rustc_builtin_macros/src/cfg_eval.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,17 +2,18 @@ use crate::util::check_builtin_macro_attribute;

use rustc_ast as ast;
use rustc_ast::mut_visit::MutVisitor;
use rustc_ast::ptr::P;
use rustc_ast::tokenstream::CanSynthesizeMissingTokens;
use rustc_ast::visit::Visitor;
use rustc_ast::{mut_visit, visit};
use rustc_ast::{AstLike, Attribute};
use rustc_expand::base::{Annotatable, ExtCtxt};
use rustc_expand::config::StripUnconfigured;
use rustc_expand::configure;
use rustc_feature::Features;
use rustc_parse::parser::ForceCollect;
use rustc_session::utils::FlattenNonterminals;

use rustc_ast::ptr::P;
use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_span::Span;
use smallvec::SmallVec;
Expand All @@ -24,19 +25,16 @@ crate fn expand(
annotatable: Annotatable,
) -> Vec<Annotatable> {
check_builtin_macro_attribute(ecx, meta_item, sym::cfg_eval);
cfg_eval(ecx, annotatable)
vec![cfg_eval(ecx.sess, ecx.ecfg.features, annotatable)]
}

crate fn cfg_eval(ecx: &ExtCtxt<'_>, annotatable: Annotatable) -> Vec<Annotatable> {
let mut visitor = CfgEval {
cfg: &mut StripUnconfigured {
sess: ecx.sess,
features: ecx.ecfg.features,
config_tokens: true,
},
};
let annotatable = visitor.configure_annotatable(annotatable);
vec![annotatable]
crate fn cfg_eval(
sess: &Session,
features: Option<&Features>,
annotatable: Annotatable,
) -> Annotatable {
CfgEval { cfg: &mut StripUnconfigured { sess, features, config_tokens: true } }
.configure_annotatable(annotatable)
}

struct CfgEval<'a, 'b> {
Expand Down
40 changes: 34 additions & 6 deletions compiler/rustc_builtin_macros/src/derive.rs
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@@ -1,12 +1,13 @@
use crate::cfg_eval::cfg_eval;

use rustc_ast::{self as ast, attr, token, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
use rustc_ast as ast;
use rustc_ast::{attr, token, GenericParamKind, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
use rustc_errors::{struct_span_err, Applicability};
use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
use rustc_feature::AttributeTemplate;
use rustc_parse::validate_attr;
use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_span::symbol::{sym, Ident};
use rustc_span::Span;

crate struct Expander;
Expand All @@ -26,6 +27,7 @@ impl MultiItemModifier for Expander {
return ExpandResult::Ready(vec![item]);
}

let (sess, features) = (ecx.sess, ecx.ecfg.features);
let result =
ecx.resolver.resolve_derives(ecx.current_expansion.id, ecx.force_mode, &|| {
let template =
Expand All @@ -38,7 +40,8 @@ impl MultiItemModifier for Expander {
template,
);

attr.meta_item_list()
let mut resolutions: Vec<_> = attr
.meta_item_list()
.unwrap_or_default()
.into_iter()
.filter_map(|nested_meta| match nested_meta {
Expand All @@ -54,17 +57,42 @@ impl MultiItemModifier for Expander {
report_path_args(sess, &meta);
meta.path
})
.map(|path| (path, None))
.collect()
.map(|path| (path, dummy_annotatable(), None))
.collect();

// Do not configure or clone items unless necessary.
match &mut resolutions[..] {
[] => {}
[(_, first_item, _), others @ ..] => {
*first_item = cfg_eval(sess, features, item.clone());
for (_, item, _) in others {
*item = first_item.clone();
}
}
}

resolutions
});

match result {
Ok(()) => ExpandResult::Ready(cfg_eval(ecx, item)),
Ok(()) => ExpandResult::Ready(vec![item]),
Err(Indeterminate) => ExpandResult::Retry(item),
}
}
}

// The cheapest `Annotatable` to construct.
fn dummy_annotatable() -> Annotatable {
Annotatable::GenericParam(ast::GenericParam {
id: ast::DUMMY_NODE_ID,
ident: Ident::invalid(),
attrs: Default::default(),
bounds: Default::default(),
is_placeholder: false,
kind: GenericParamKind::Lifetime,
})
}

fn report_bad_target(sess: &Session, item: &Annotatable, span: Span) -> bool {
let item_kind = match item {
Annotatable::Item(item) => Some(&item.kind),
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_expand/src/base.rs
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Expand Up @@ -835,7 +835,7 @@ impl SyntaxExtension {
/// Error type that denotes indeterminacy.
pub struct Indeterminate;

pub type DeriveResolutions = Vec<(ast::Path, Option<Lrc<SyntaxExtension>>)>;
pub type DeriveResolutions = Vec<(ast::Path, Annotatable, Option<Lrc<SyntaxExtension>>)>;

pub trait ResolverExpand {
fn next_node_id(&mut self) -> NodeId;
Expand Down
30 changes: 2 additions & 28 deletions compiler/rustc_expand/src/expand.rs
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Expand Up @@ -500,42 +500,16 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
.resolver
.take_derive_resolutions(expn_id)
.map(|derives| {
enum AnnotatableRef<'a> {
Item(&'a P<ast::Item>),
Stmt(&'a ast::Stmt),
}
let item = match &fragment {
AstFragment::Items(items) => match &items[..] {
[item] => AnnotatableRef::Item(item),
_ => unreachable!(),
},
AstFragment::Stmts(stmts) => match &stmts[..] {
[stmt] => AnnotatableRef::Stmt(stmt),
_ => unreachable!(),
},
_ => unreachable!(),
};

derive_invocations.reserve(derives.len());
derives
.into_iter()
.map(|(path, _exts)| {
.map(|(path, item, _exts)| {
// FIXME: Consider using the derive resolutions (`_exts`)
// instead of enqueuing the derives to be resolved again later.
let expn_id = ExpnId::fresh(None);
derive_invocations.push((
Invocation {
kind: InvocationKind::Derive {
path,
item: match item {
AnnotatableRef::Item(item) => {
Annotatable::Item(item.clone())
}
AnnotatableRef::Stmt(stmt) => {
Annotatable::Stmt(P(stmt.clone()))
}
},
},
kind: InvocationKind::Derive { path, item },
fragment_kind,
expansion_data: ExpansionData {
id: expn_id,
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_resolve/src/macros.rs
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Expand Up @@ -380,7 +380,7 @@ impl<'a> ResolverExpand for Resolver<'a> {
has_derive_copy: false,
});
let parent_scope = self.invocation_parent_scopes[&expn_id];
for (i, (path, opt_ext)) in entry.resolutions.iter_mut().enumerate() {
for (i, (path, _, opt_ext)) in entry.resolutions.iter_mut().enumerate() {
if opt_ext.is_none() {
*opt_ext = Some(
match self.resolve_macro_path(
Expand Down
48 changes: 46 additions & 2 deletions src/test/ui/proc-macro/attribute-after-derive.stdout
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Expand Up @@ -130,7 +130,7 @@ PRINT-DERIVE INPUT (DEBUG): TokenStream [
span: $DIR/attribute-after-derive.rs:25:24: 28:2 (#0),
},
]
PRINT-ATTR INPUT (DISPLAY): struct DeriveAttribute { }
PRINT-ATTR INPUT (DISPLAY): struct DeriveAttribute { #[cfg(FALSE)] field : u8, }
PRINT-ATTR INPUT (DEBUG): TokenStream [
Ident {
ident: "struct",
Expand All @@ -142,7 +142,51 @@ PRINT-ATTR INPUT (DEBUG): TokenStream [
},
Group {
delimiter: Brace,
stream: TokenStream [],
stream: TokenStream [
Punct {
ch: '#',
spacing: Alone,
span: $DIR/attribute-after-derive.rs:26:5: 26:6 (#0),
},
Group {
delimiter: Bracket,
stream: TokenStream [
Ident {
ident: "cfg",
span: $DIR/attribute-after-derive.rs:26:7: 26:10 (#0),
},
Group {
delimiter: Parenthesis,
stream: TokenStream [
Ident {
ident: "FALSE",
span: $DIR/attribute-after-derive.rs:26:11: 26:16 (#0),
},
],
span: $DIR/attribute-after-derive.rs:26:10: 26:17 (#0),
},
],
span: $DIR/attribute-after-derive.rs:26:6: 26:18 (#0),
},
Ident {
ident: "field",
span: $DIR/attribute-after-derive.rs:27:5: 27:10 (#0),
},
Punct {
ch: ':',
spacing: Alone,
span: $DIR/attribute-after-derive.rs:27:10: 27:11 (#0),
},
Ident {
ident: "u8",
span: $DIR/attribute-after-derive.rs:27:12: 27:14 (#0),
},
Punct {
ch: ',',
spacing: Alone,
span: $DIR/attribute-after-derive.rs:27:14: 27:15 (#0),
},
],
span: $DIR/attribute-after-derive.rs:25:24: 28:2 (#0),
},
]