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Rollup merge of rust-lang#49350 - abonander:macros-in-extern, r=petro…
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…chenkov

Expand macros in `extern {}` blocks

This permits macro and proc-macro and attribute invocations (the latter only with the `proc_macro` feature of course) in `extern {}` blocks, gated behind a new `macros_in_extern` feature.

A tracking issue is now open at rust-lang#49476

closes rust-lang#48747
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alexcrichton authored Apr 5, 2018
2 parents b0bd9a7 + 5d74990 commit 46492ff
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Showing 31 changed files with 544 additions and 65 deletions.
1 change: 1 addition & 0 deletions src/librustc/hir/lowering.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2724,6 +2724,7 @@ impl<'a> LoweringContext<'a> {
hir::ForeignItemStatic(this.lower_ty(t, ImplTraitContext::Disallowed), m)
}
ForeignItemKind::Ty => hir::ForeignItemType,
ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
},
vis: this.lower_visibility(&i.vis, None),
span: i.span,
Expand Down
4 changes: 4 additions & 0 deletions src/librustc/hir/map/def_collector.rs
Original file line number Diff line number Diff line change
Expand Up @@ -181,6 +181,10 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
}

fn visit_foreign_item(&mut self, foreign_item: &'a ForeignItem) {
if let ForeignItemKind::Macro(_) = foreign_item.node {
return self.visit_macro_invoc(foreign_item.id, false);
}

let def = self.create_def(foreign_item.id,
DefPathData::ValueNs(foreign_item.ident.name.as_str()),
REGULAR_SPACE,
Expand Down
18 changes: 17 additions & 1 deletion src/librustc_passes/ast_validation.rs
Original file line number Diff line number Diff line change
Expand Up @@ -381,7 +381,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
.span_label(span, "pattern not allowed in foreign function").emit();
});
}
ForeignItemKind::Static(..) | ForeignItemKind::Ty => {}
ForeignItemKind::Static(..) | ForeignItemKind::Ty | ForeignItemKind::Macro(..) => {}
}

visit::walk_foreign_item(self, fi)
Expand Down Expand Up @@ -460,6 +460,14 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.check_late_bound_lifetime_defs(&t.bound_generic_params);
visit::walk_poly_trait_ref(self, t, m);
}

fn visit_mac(&mut self, mac: &Spanned<Mac_>) {
// when a new macro kind is added but the author forgets to set it up for expansion
// because that's the only part that won't cause a compiler error
self.session.diagnostic()
.span_bug(mac.span, "macro invocation missed in expansion; did you forget to override \
the relevant `fold_*()` method in `PlaceholderExpander`?");
}
}

// Bans nested `impl Trait`, e.g. `impl Into<impl Debug>`.
Expand Down Expand Up @@ -522,6 +530,10 @@ impl<'a> Visitor<'a> for NestedImplTraitVisitor<'a> {
}
}
}

fn visit_mac(&mut self, _mac: &Spanned<Mac_>) {
// covered in AstValidator
}
}

// Bans `impl Trait` in path projections like `<impl Iterator>::Item` or `Foo::Bar<impl Trait>`.
Expand Down Expand Up @@ -583,6 +595,10 @@ impl<'a> Visitor<'a> for ImplTraitProjectionVisitor<'a> {
_ => visit::walk_ty(self, t),
}
}

fn visit_mac(&mut self, _mac: &Spanned<Mac_>) {
// covered in AstValidator
}
}

pub fn check_crate(session: &Session, krate: &Crate) {
Expand Down
6 changes: 6 additions & 0 deletions src/librustc_resolve/build_reduced_graph.rs
Original file line number Diff line number Diff line change
Expand Up @@ -456,6 +456,7 @@ impl<'a> Resolver<'a> {
ForeignItemKind::Ty => {
(Def::TyForeign(self.definitions.local_def_id(item.id)), TypeNS)
}
ForeignItemKind::Macro(_) => unreachable!(),
};
let parent = self.current_module;
let vis = self.resolve_visibility(&item.vis);
Expand Down Expand Up @@ -816,6 +817,11 @@ impl<'a, 'b> Visitor<'a> for BuildReducedGraphVisitor<'a, 'b> {
}

fn visit_foreign_item(&mut self, foreign_item: &'a ForeignItem) {
if let ForeignItemKind::Macro(_) = foreign_item.node {
self.visit_invoc(foreign_item.id);
return;
}

self.resolver.build_reduced_graph_for_foreign_item(foreign_item, self.expansion);
visit::walk_foreign_item(self, foreign_item);
}
Expand Down
1 change: 1 addition & 0 deletions src/librustc_resolve/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -863,6 +863,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Resolver<'a> {
}
ForeignItemKind::Static(..) => NoTypeParameters,
ForeignItemKind::Ty => NoTypeParameters,
ForeignItemKind::Macro(..) => NoTypeParameters,
};
self.with_type_parameter_rib(type_parameters, |this| {
visit::walk_foreign_item(this, foreign_item);
Expand Down
1 change: 1 addition & 0 deletions src/librustc_save_analysis/dump_visitor.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1812,6 +1812,7 @@ impl<'l, 'tcx: 'l, 'll, O: DumpOutput + 'll> Visitor<'l> for DumpVisitor<'l, 'tc
self.dumper.dump_def(&access, var_data);
}
}
ast::ForeignItemKind::Macro(..) => {}
}
}
}
1 change: 1 addition & 0 deletions src/librustc_save_analysis/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -182,6 +182,7 @@ impl<'l, 'tcx: 'l> SaveContext<'l, 'tcx> {
}
// FIXME(plietar): needs a new DefKind in rls-data
ast::ForeignItemKind::Ty => None,
ast::ForeignItemKind::Macro(..) => None,
}
}

Expand Down
1 change: 1 addition & 0 deletions src/librustc_save_analysis/sig.rs
Original file line number Diff line number Diff line change
Expand Up @@ -822,6 +822,7 @@ impl Sig for ast::ForeignItem {
refs: vec![],
})
}
ast::ForeignItemKind::Macro(..) => Err("macro"),
}
}
}
Expand Down
3 changes: 3 additions & 0 deletions src/libsyntax/ast.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2192,6 +2192,8 @@ pub enum ForeignItemKind {
Static(P<Ty>, bool),
/// A foreign type
Ty,
/// A macro invocation
Macro(Mac),
}

impl ForeignItemKind {
Expand All @@ -2200,6 +2202,7 @@ impl ForeignItemKind {
ForeignItemKind::Fn(..) => "foreign function",
ForeignItemKind::Static(..) => "foreign static item",
ForeignItemKind::Ty => "foreign type",
ForeignItemKind::Macro(..) => "macro in foreign module",
}
}
}
Expand Down
28 changes: 28 additions & 0 deletions src/libsyntax/ext/base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@ pub enum Annotatable {
Item(P<ast::Item>),
TraitItem(P<ast::TraitItem>),
ImplItem(P<ast::ImplItem>),
ForeignItem(P<ast::ForeignItem>),
Stmt(P<ast::Stmt>),
Expr(P<ast::Expr>),
}
Expand All @@ -48,6 +49,7 @@ impl HasAttrs for Annotatable {
Annotatable::Item(ref item) => &item.attrs,
Annotatable::TraitItem(ref trait_item) => &trait_item.attrs,
Annotatable::ImplItem(ref impl_item) => &impl_item.attrs,
Annotatable::ForeignItem(ref foreign_item) => &foreign_item.attrs,
Annotatable::Stmt(ref stmt) => stmt.attrs(),
Annotatable::Expr(ref expr) => &expr.attrs,
}
Expand All @@ -58,6 +60,8 @@ impl HasAttrs for Annotatable {
Annotatable::Item(item) => Annotatable::Item(item.map_attrs(f)),
Annotatable::TraitItem(trait_item) => Annotatable::TraitItem(trait_item.map_attrs(f)),
Annotatable::ImplItem(impl_item) => Annotatable::ImplItem(impl_item.map_attrs(f)),
Annotatable::ForeignItem(foreign_item) =>
Annotatable::ForeignItem(foreign_item.map_attrs(f)),
Annotatable::Stmt(stmt) => Annotatable::Stmt(stmt.map_attrs(f)),
Annotatable::Expr(expr) => Annotatable::Expr(expr.map_attrs(f)),
}
Expand All @@ -70,6 +74,7 @@ impl Annotatable {
Annotatable::Item(ref item) => item.span,
Annotatable::TraitItem(ref trait_item) => trait_item.span,
Annotatable::ImplItem(ref impl_item) => impl_item.span,
Annotatable::ForeignItem(ref foreign_item) => foreign_item.span,
Annotatable::Stmt(ref stmt) => stmt.span,
Annotatable::Expr(ref expr) => expr.span,
}
Expand Down Expand Up @@ -106,6 +111,13 @@ impl Annotatable {
}
}

pub fn expect_foreign_item(self) -> ast::ForeignItem {
match self {
Annotatable::ForeignItem(i) => i.into_inner(),
_ => panic!("expected foreign item")
}
}

pub fn derive_allowed(&self) -> bool {
match *self {
Annotatable::Item(ref item) => match item.node {
Expand Down Expand Up @@ -317,6 +329,9 @@ pub trait MacResult {
None
}

/// Create zero or more items in an `extern {}` block
fn make_foreign_items(self: Box<Self>) -> Option<SmallVector<ast::ForeignItem>> { None }

/// Create a pattern.
fn make_pat(self: Box<Self>) -> Option<P<ast::Pat>> {
None
Expand Down Expand Up @@ -365,6 +380,7 @@ make_MacEager! {
items: SmallVector<P<ast::Item>>,
impl_items: SmallVector<ast::ImplItem>,
trait_items: SmallVector<ast::TraitItem>,
foreign_items: SmallVector<ast::ForeignItem>,
stmts: SmallVector<ast::Stmt>,
ty: P<ast::Ty>,
}
Expand All @@ -386,6 +402,10 @@ impl MacResult for MacEager {
self.trait_items
}

fn make_foreign_items(self: Box<Self>) -> Option<SmallVector<ast::ForeignItem>> {
self.foreign_items
}

fn make_stmts(self: Box<Self>) -> Option<SmallVector<ast::Stmt>> {
match self.stmts.as_ref().map_or(0, |s| s.len()) {
0 => make_stmts_default!(self),
Expand Down Expand Up @@ -502,6 +522,14 @@ impl MacResult for DummyResult {
}
}

fn make_foreign_items(self: Box<Self>) -> Option<SmallVector<ast::ForeignItem>> {
if self.expr_only {
None
} else {
Some(SmallVector::new())
}
}

fn make_stmts(self: Box<DummyResult>) -> Option<SmallVector<ast::Stmt>> {
Some(SmallVector::one(ast::Stmt {
id: ast::DUMMY_NODE_ID,
Expand Down
58 changes: 58 additions & 0 deletions src/libsyntax/ext/expand.rs
Original file line number Diff line number Diff line change
Expand Up @@ -133,6 +133,8 @@ expansions! {
"trait item", .make_trait_items, lift .fold_trait_item, lift .visit_trait_item;
ImplItems: SmallVector<ast::ImplItem> [SmallVector, ast::ImplItem],
"impl item", .make_impl_items, lift .fold_impl_item, lift .visit_impl_item;
ForeignItems: SmallVector<ast::ForeignItem> [SmallVector, ast::ForeignItem],
"foreign item", .make_foreign_items, lift .fold_foreign_item, lift .visit_foreign_item;
}

impl ExpansionKind {
Expand All @@ -149,6 +151,8 @@ impl ExpansionKind {
Expansion::ImplItems(items.map(Annotatable::expect_impl_item).collect()),
ExpansionKind::TraitItems =>
Expansion::TraitItems(items.map(Annotatable::expect_trait_item).collect()),
ExpansionKind::ForeignItems =>
Expansion::ForeignItems(items.map(Annotatable::expect_foreign_item).collect()),
_ => unreachable!(),
}
}
Expand Down Expand Up @@ -435,6 +439,11 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
Annotatable::ImplItem(item) => {
Annotatable::ImplItem(item.map(|item| cfg.fold_impl_item(item).pop().unwrap()))
}
Annotatable::ForeignItem(item) => {
Annotatable::ForeignItem(
item.map(|item| cfg.fold_foreign_item(item).pop().unwrap())
)
}
Annotatable::Stmt(stmt) => {
Annotatable::Stmt(stmt.map(|stmt| cfg.fold_stmt(stmt).pop().unwrap()))
}
Expand Down Expand Up @@ -509,6 +518,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
Annotatable::Item(item) => token::NtItem(item),
Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
Annotatable::Expr(expr) => token::NtExpr(expr),
})).into();
Expand Down Expand Up @@ -793,6 +803,15 @@ impl<'a> Parser<'a> {
}
Expansion::ImplItems(items)
}
ExpansionKind::ForeignItems => {
let mut items = SmallVector::new();
while self.token != token::Eof {
if let Some(item) = self.parse_foreign_item()? {
items.push(item);
}
}
Expansion::ForeignItems(items)
}
ExpansionKind::Stmts => {
let mut stmts = SmallVector::new();
while self.token != token::Eof &&
Expand Down Expand Up @@ -1166,6 +1185,44 @@ impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
noop_fold_foreign_mod(self.cfg.configure_foreign_mod(foreign_mod), self)
}

fn fold_foreign_item(&mut self,
foreign_item: ast::ForeignItem) -> SmallVector<ast::ForeignItem> {
let (attr, traits, foreign_item) = self.classify_item(foreign_item);

let explain = if self.cx.ecfg.proc_macro_enabled() {
feature_gate::EXPLAIN_PROC_MACROS_IN_EXTERN
} else {
feature_gate::EXPLAIN_MACROS_IN_EXTERN
};

if attr.is_some() || !traits.is_empty() {
if !self.cx.ecfg.macros_in_extern_enabled() {
if let Some(ref attr) = attr {
emit_feature_err(&self.cx.parse_sess, "macros_in_extern", attr.span,
GateIssue::Language, explain);
}
}

let item = Annotatable::ForeignItem(P(foreign_item));
return self.collect_attr(attr, traits, item, ExpansionKind::ForeignItems)
.make_foreign_items();
}

if let ast::ForeignItemKind::Macro(mac) = foreign_item.node {
self.check_attributes(&foreign_item.attrs);

if !self.cx.ecfg.macros_in_extern_enabled() {
emit_feature_err(&self.cx.parse_sess, "macros_in_extern", foreign_item.span,
GateIssue::Language, explain);
}

return self.collect_bang(mac, foreign_item.span, ExpansionKind::ForeignItems)
.make_foreign_items();
}

noop_fold_foreign_item(foreign_item, self)
}

fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
match item {
ast::ItemKind::MacroDef(..) => item,
Expand Down Expand Up @@ -1311,6 +1368,7 @@ impl<'feat> ExpansionConfig<'feat> {
fn enable_allow_internal_unstable = allow_internal_unstable,
fn enable_custom_derive = custom_derive,
fn proc_macro_enabled = proc_macro,
fn macros_in_extern_enabled = macros_in_extern,
}
}

Expand Down
11 changes: 11 additions & 0 deletions src/libsyntax/ext/placeholders.rs
Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,10 @@ pub fn placeholder(kind: ExpansionKind, id: ast::NodeId) -> Expansion {
defaultness: ast::Defaultness::Final,
tokens: None,
})),
ExpansionKind::ForeignItems => Expansion::ForeignItems(SmallVector::one(ast::ForeignItem {
id, span, ident, vis, attrs,
node: ast::ForeignItemKind::Macro(mac_placeholder()),
})),
ExpansionKind::Pat => Expansion::Pat(P(ast::Pat {
id, span, node: ast::PatKind::Mac(mac_placeholder()),
})),
Expand Down Expand Up @@ -132,6 +136,13 @@ impl<'a, 'b> Folder for PlaceholderExpander<'a, 'b> {
}
}

fn fold_foreign_item(&mut self, item: ast::ForeignItem) -> SmallVector<ast::ForeignItem> {
match item.node {
ast::ForeignItemKind::Macro(_) => self.remove(item.id).make_foreign_items(),
_ => noop_fold_foreign_item(item, self),
}
}

fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
match expr.node {
ast::ExprKind::Mac(_) => self.remove(expr.id).make_expr(),
Expand Down
11 changes: 11 additions & 0 deletions src/libsyntax/feature_gate.rs
Original file line number Diff line number Diff line change
Expand Up @@ -443,6 +443,9 @@ declare_features! (

// Allows keywords to be escaped for use as identifiers
(active, raw_identifiers, "1.26.0", Some(48589), None),

// Allows macro invocations in `extern {}` blocks
(active, macros_in_extern, "1.27.0", Some(49476), None),
);

declare_features! (
Expand Down Expand Up @@ -1291,6 +1294,13 @@ pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
"Using the `?` macro Kleene operator for \"at most one\" repetition is unstable";

pub const EXPLAIN_MACROS_IN_EXTERN: &'static str =
"Macro invocations in `extern {}` blocks are experimental.";

// mention proc-macros when enabled
pub const EXPLAIN_PROC_MACROS_IN_EXTERN: &'static str =
"Macro and proc-macro invocations in `extern {}` blocks are experimental.";

struct PostExpansionVisitor<'a> {
context: &'a Context<'a>,
}
Expand Down Expand Up @@ -1595,6 +1605,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
gate_feature_post!(&self, extern_types, i.span,
"extern types are experimental");
}
ast::ForeignItemKind::Macro(..) => {}
}

visit::walk_foreign_item(self, i)
Expand Down
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