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parser_fn_front_matter: allow const .. extern
This commit is contained in:
Mazdak Farrokhzad
parent
c30f068dc8
commit
36a17e4067
@ -798,12 +798,12 @@ impl<'a> Parser<'a> {
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let defaultness = self.parse_defaultness();
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let (name, kind, generics) = if self.eat_keyword(kw::Type) {
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self.parse_assoc_ty()?
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} else if self.is_const_item() {
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self.parse_assoc_const()?
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} else if self.is_fn_front_matter() {
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self.parse_assoc_fn(at_end, &mut attrs, is_name_required)?
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} else if let Some(mac) = self.parse_assoc_macro_invoc("associated", Some(&vis), at_end)? {
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(Ident::invalid(), AssocItemKind::Macro(mac), Generics::default())
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} else {
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self.parse_assoc_fn(at_end, &mut attrs, is_name_required)?
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self.parse_assoc_const()?
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};
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Ok(AssocItem {
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@ -819,12 +819,6 @@ impl<'a> Parser<'a> {
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})
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}
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/// Returns `true` if we are looking at `const ID`
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/// (returns `false` for things like `const fn`, etc.).
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fn is_const_item(&self) -> bool {
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self.token.is_keyword(kw::Const) && !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
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}
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/// This parses the grammar:
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///
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/// AssocConst = "const" Ident ":" Ty "=" Expr ";"
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@ -1034,21 +1028,20 @@ impl<'a> Parser<'a> {
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let attrs = self.parse_outer_attributes()?;
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let lo = self.token.span;
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let visibility = self.parse_visibility(FollowedByType::No)?;
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let vis = self.parse_visibility(FollowedByType::No)?;
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// FOREIGN TYPE ITEM
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if self.check_keyword(kw::Type) {
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return self.parse_item_foreign_type(visibility, lo, attrs);
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}
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// FOREIGN STATIC ITEM
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if self.is_static_global() {
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// FOREIGN TYPE ITEM
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self.parse_item_foreign_type(vis, lo, attrs)
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} else if self.is_fn_front_matter() {
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// FOREIGN FUNCTION ITEM
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self.parse_item_foreign_fn(vis, lo, attrs)
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} else if self.is_static_global() {
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// FOREIGN STATIC ITEM
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self.bump(); // `static`
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return self.parse_item_foreign_static(visibility, lo, attrs);
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}
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// Treat `const` as `static` for error recovery, but don't add it to expected tokens.
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if self.is_kw_followed_by_ident(kw::Const) {
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self.parse_item_foreign_static(vis, lo, attrs)
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} else if self.token.is_keyword(kw::Const) {
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// Treat `const` as `static` for error recovery, but don't add it to expected tokens.
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self.bump(); // `const`
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self.struct_span_err(self.prev_span, "extern items cannot be `const`")
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.span_suggestion(
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@ -1058,32 +1051,17 @@ impl<'a> Parser<'a> {
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Applicability::MachineApplicable,
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)
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.emit();
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return self.parse_item_foreign_static(visibility, lo, attrs);
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}
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// FOREIGN FUNCTION ITEM
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const MAY_INTRODUCE_FN: &[Symbol] = &[kw::Const, kw::Async, kw::Unsafe, kw::Extern, kw::Fn];
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if MAY_INTRODUCE_FN.iter().any(|&kw| self.check_keyword(kw)) {
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return self.parse_item_foreign_fn(visibility, lo, attrs);
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}
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match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
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Some(mac) => Ok(P(ForeignItem {
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ident: Ident::invalid(),
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span: lo.to(self.prev_span),
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id: DUMMY_NODE_ID,
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attrs,
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vis: visibility,
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kind: ForeignItemKind::Macro(mac),
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tokens: None,
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})),
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None => {
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if !attrs.is_empty() {
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self.expected_item_err(&attrs)?;
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}
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self.unexpected()
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self.parse_item_foreign_static(vis, lo, attrs)
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} else if let Some(mac) = self.parse_assoc_macro_invoc("extern", Some(&vis), &mut false)? {
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let kind = ForeignItemKind::Macro(mac);
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let span = lo.to(self.prev_span);
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let ident = Ident::invalid();
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Ok(P(ForeignItem { ident, span, id: DUMMY_NODE_ID, attrs, vis, kind, tokens: None }))
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} else {
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if !attrs.is_empty() {
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self.expected_item_err(&attrs)?;
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}
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self.unexpected()
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}
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}
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@ -1752,6 +1730,29 @@ impl<'a> Parser<'a> {
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Ok(body)
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}
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/// Is the current token unambiguously the start of an `FnHeader`?
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fn is_fn_front_matter(&mut self) -> bool {
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// We use an over-approximation here.
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// `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
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// This works for `async fn` and similar as `async async` is an invalid
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// parse and `async fn` is never a valid parse on previous editions.
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const QUALIFIER: [Symbol; 4] = [kw::Const, kw::Async, kw::Unsafe, kw::Extern];
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let check_qual_follow = |this: &mut Self, dist| {
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this.look_ahead(dist, |t| {
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// ...qualified and then `fn`, e.g. `const fn`.
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t.is_keyword(kw::Fn)
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// Two qualifiers. This is enough.
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|| QUALIFIER.iter().any(|&kw| t.is_keyword(kw))
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})
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};
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self.check_keyword(kw::Fn) // Definitely an `fn`.
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// `$qual fn` or `$qual $qual`:
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|| QUALIFIER.iter().any(|&kw| self.check_keyword(kw)) && check_qual_follow(self, 1)
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// `extern ABI fn` or `extern ABI $qual`; skip 1 for the ABI.
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|| self.check_keyword(kw::Extern) && check_qual_follow(self, 2)
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}
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/// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
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/// up to and including the `fn` keyword. The formal grammar is:
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///
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@ -1763,16 +1764,13 @@ impl<'a> Parser<'a> {
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fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
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let constness = self.parse_constness();
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let asyncness = self.parse_asyncness();
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let unsafety = self.parse_unsafety();
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let ext = self.parse_extern()?;
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if let Async::Yes { span, .. } = asyncness {
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self.ban_async_in_2015(span);
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}
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let unsafety = self.parse_unsafety();
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let (constness, unsafety, ext) = if let Const::Yes(_) = constness {
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(constness, unsafety, Extern::None)
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} else {
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let ext = self.parse_extern()?;
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(Const::No, unsafety, ext)
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};
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if !self.eat_keyword(kw::Fn) {
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// It is possible for `expect_one_of` to recover given the contents of
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// `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
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@ -1781,6 +1779,7 @@ impl<'a> Parser<'a> {
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unreachable!()
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}
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}
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Ok(FnHeader { constness, unsafety, asyncness, ext })
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}
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@ -199,7 +199,7 @@ impl<'a> Parser<'a> {
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}
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}
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pub(super) fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
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fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
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self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
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}
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@ -6,6 +6,5 @@ trait T {
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});
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//~^ ERROR expected one of `async`
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//~| ERROR expected one of `.`, `;`, `?`, `else`, or an operator, found `}`
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//~| ERROR expected identifier, found `;`
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Some(4)
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}
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@ -13,11 +13,5 @@ LL | let _ = if true {
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LL | });
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| ^ help: `}` may belong here
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error: expected identifier, found `;`
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--> $DIR/issue-60075.rs:6:11
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LL | });
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| ^ expected identifier
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error: aborting due to 3 previous errors
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error: aborting due to 2 previous errors
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@ -18,9 +18,9 @@ fn main() {
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unsafe fn ft2(); // OK.
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const fn ft3(); //~ ERROR trait fns cannot be declared const
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extern "C" fn ft4(); // OK.
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/* const */ async unsafe extern "C" fn ft5();
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const async unsafe extern "C" fn ft5();
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//~^ ERROR trait fns cannot be declared `async`
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//^ FIXME(Centril): `const` should be legal syntactically, ensure it's illegal semantically.
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//~| ERROR trait fns cannot be declared const
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}
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struct Y;
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@ -30,10 +30,10 @@ fn main() {
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unsafe fn ft2() {} // OK.
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const fn ft3() {} //~ ERROR trait fns cannot be declared const
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extern "C" fn ft4() {}
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/* const */ async unsafe extern "C" fn ft5() {}
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const async unsafe extern "C" fn ft5() {}
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//~^ ERROR trait fns cannot be declared `async`
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//~| ERROR trait fns cannot be declared const
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//~| ERROR method `ft5` has an incompatible type for trait
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//^ FIXME(Centril): `const` should be legal syntactically, ensure it's illegal semantically.
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}
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impl Y {
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@ -41,8 +41,7 @@ fn main() {
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unsafe fn fi2() {} // OK.
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const fn fi3() {} // OK.
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extern "C" fn fi4() {} // OK.
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/* const */ async unsafe extern "C" fn fi5() {} // OK.
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//^ FIXME(Centril): `const` should be legal syntactically, ensure it's illegal semantically.
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const async unsafe extern "C" fn fi5() {} // OK.
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}
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extern {
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@ -50,8 +49,6 @@ fn main() {
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unsafe fn fe2(); //~ ERROR functions in `extern` blocks cannot have qualifiers
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const fn fe3(); //~ ERROR functions in `extern` blocks cannot have qualifiers
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extern "C" fn fe4(); //~ ERROR functions in `extern` blocks cannot have qualifiers
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/* const */ async unsafe extern "C" fn fe5();
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//~^ ERROR functions in `extern` blocks cannot have qualifiers
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//^ FIXME(Centril): `const` should be legal syntactically, ensure it's illegal semantically.
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const async unsafe extern "C" fn fe5(); //~ ERROR functions in `extern` blocks
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}
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}
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@ -15,13 +15,19 @@ error[E0379]: trait fns cannot be declared const
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LL | const fn ft3();
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| ^^^^^ trait fns cannot be const
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error[E0706]: trait fns cannot be declared `async`
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--> $DIR/fn-header-semantic-fail.rs:21:21
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error[E0379]: trait fns cannot be declared const
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--> $DIR/fn-header-semantic-fail.rs:21:9
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LL | /* const */ async unsafe extern "C" fn ft5();
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| -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| |
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| `async` because of this
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LL | const async unsafe extern "C" fn ft5();
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| ^^^^^ trait fns cannot be const
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error[E0706]: trait fns cannot be declared `async`
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--> $DIR/fn-header-semantic-fail.rs:21:9
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LL | const async unsafe extern "C" fn ft5();
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| ^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| |
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| `async` because of this
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= note: `async` trait functions are not currently supported
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= note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
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@ -43,19 +49,25 @@ error[E0379]: trait fns cannot be declared const
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LL | const fn ft3() {}
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| ^^^^^ trait fns cannot be const
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error[E0706]: trait fns cannot be declared `async`
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--> $DIR/fn-header-semantic-fail.rs:33:21
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error[E0379]: trait fns cannot be declared const
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--> $DIR/fn-header-semantic-fail.rs:33:9
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LL | /* const */ async unsafe extern "C" fn ft5() {}
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| -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| |
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| `async` because of this
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LL | const async unsafe extern "C" fn ft5() {}
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| ^^^^^ trait fns cannot be const
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error[E0706]: trait fns cannot be declared `async`
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--> $DIR/fn-header-semantic-fail.rs:33:9
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LL | const async unsafe extern "C" fn ft5() {}
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| ^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| |
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| `async` because of this
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= note: `async` trait functions are not currently supported
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= note: consider using the `async-trait` crate: https://crates.io/crates/async-trait
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error: functions in `extern` blocks cannot have qualifiers
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--> $DIR/fn-header-semantic-fail.rs:49:18
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--> $DIR/fn-header-semantic-fail.rs:48:18
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LL | extern {
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| ------ in this `extern` block
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@ -65,7 +77,7 @@ LL | async fn fe1();
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| help: remove the qualifiers: `fn`
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error: functions in `extern` blocks cannot have qualifiers
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--> $DIR/fn-header-semantic-fail.rs:50:19
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--> $DIR/fn-header-semantic-fail.rs:49:19
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LL | extern {
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| ------ in this `extern` block
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@ -76,7 +88,7 @@ LL | unsafe fn fe2();
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| help: remove the qualifiers: `fn`
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error: functions in `extern` blocks cannot have qualifiers
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--> $DIR/fn-header-semantic-fail.rs:51:18
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--> $DIR/fn-header-semantic-fail.rs:50:18
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|
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LL | extern {
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| ------ in this `extern` block
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@ -87,7 +99,7 @@ LL | const fn fe3();
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| help: remove the qualifiers: `fn`
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error: functions in `extern` blocks cannot have qualifiers
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--> $DIR/fn-header-semantic-fail.rs:52:23
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--> $DIR/fn-header-semantic-fail.rs:51:23
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|
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LL | extern {
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| ------ in this `extern` block
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@ -98,15 +110,15 @@ LL | extern "C" fn fe4();
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| help: remove the qualifiers: `fn`
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error: functions in `extern` blocks cannot have qualifiers
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--> $DIR/fn-header-semantic-fail.rs:53:48
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--> $DIR/fn-header-semantic-fail.rs:52:42
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|
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LL | extern {
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| ------ in this `extern` block
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...
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LL | /* const */ async unsafe extern "C" fn fe5();
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| ---------------------------^^^
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| |
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| help: remove the qualifiers: `fn`
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LL | const async unsafe extern "C" fn fe5();
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| ---------------------------------^^^
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| |
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| help: remove the qualifiers: `fn`
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error[E0053]: method `ft1` has an incompatible type for trait
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--> $DIR/fn-header-semantic-fail.rs:28:24
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@ -124,21 +136,21 @@ LL | async fn ft1() {}
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found fn pointer `fn() -> impl std::future::Future`
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error[E0053]: method `ft5` has an incompatible type for trait
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--> $DIR/fn-header-semantic-fail.rs:33:54
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--> $DIR/fn-header-semantic-fail.rs:33:48
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|
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LL | /* const */ async unsafe extern "C" fn ft5();
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| - type in trait
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LL | const async unsafe extern "C" fn ft5();
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| - type in trait
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...
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LL | /* const */ async unsafe extern "C" fn ft5() {}
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| ^
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| |
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| the `Output` of this `async fn`'s found opaque type
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| expected `()`, found opaque type
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LL | const async unsafe extern "C" fn ft5() {}
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| ^
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| |
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| the `Output` of this `async fn`'s found opaque type
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| expected `()`, found opaque type
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|
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= note: expected fn pointer `unsafe extern "C" fn()`
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found fn pointer `unsafe extern "C" fn() -> impl std::future::Future`
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error: aborting due to 13 previous errors
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error: aborting due to 15 previous errors
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Some errors have detailed explanations: E0053, E0379, E0706.
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For more information about an error, try `rustc --explain E0053`.
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@ -22,8 +22,7 @@ fn syntax() {
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unsafe fn f();
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const fn f();
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extern "C" fn f();
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/* const */ async unsafe extern "C" fn f();
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//^ FIXME(Centril): `const` should be legal syntactically.
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const async unsafe extern "C" fn f();
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}
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impl X for Y {
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@ -31,8 +30,7 @@ fn syntax() {
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unsafe fn f();
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const fn f();
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extern "C" fn f();
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/* const */ async unsafe extern "C" fn f();
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//^ FIXME(Centril): `const` should be legal syntactically.
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const async unsafe extern "C" fn f();
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}
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impl Y {
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@ -40,8 +38,7 @@ fn syntax() {
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unsafe fn f();
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const fn f();
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extern "C" fn f();
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/* const */ async unsafe extern "C" fn f();
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//^ FIXME(Centril): `const` should be legal syntactically.
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const async unsafe extern "C" fn f();
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}
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extern {
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@ -49,7 +46,6 @@ fn syntax() {
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unsafe fn f();
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const fn f();
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extern "C" fn f();
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/* const */ async unsafe extern "C" fn f();
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//^ FIXME(Centril): `const` should be legal syntactically.
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const async unsafe extern "C" fn f();
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}
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}
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