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Rollup merge of #70421 - Centril:recover-const-async-fn-ptr, r=estebank

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parse: recover on `const fn()` / `async fn()`

Recover on `const fn()` and `async fn()` function pointers, suggesting to remove the qualifier.
For example:
```
error: an `fn` pointer type cannot be `async`
  --> $DIR/recover-const-async-fn-ptr.rs:6:11
   |
LL | type T3 = async fn();
   |           -----^^^^^
   |           |
   |           `async` because of this
   |           help: remove the `async` qualifier
```

r? @estebank
This commit is contained in:
Mazdak Farrokhzad 2020-04-02 14:27:54 +02:00 committed by GitHub
commit 03591e8a78
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 215 additions and 23 deletions
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4
src/librustc_parse/parser/item.rs
View File

@ -1496,7 +1496,7 @@ fn parse_fn_body(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, Option<P<
}
/// Is the current token the start of an `FnHeader` / not a valid parse?
fn check_fn_front_matter(&mut self) -> bool {
pub(super) fn check_fn_front_matter(&mut self) -> bool {
// We use an over-approximation here.
// `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
const QUALS: [Symbol; 4] = [kw::Const, kw::Async, kw::Unsafe, kw::Extern];
@ -1523,7 +1523,7 @@ fn check_fn_front_matter(&mut self) -> bool {
/// FnQual = "const"? "async"? "unsafe"? Extern? ;
/// FnFrontMatter = FnQual? "fn" ;
/// ```
fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
pub(super) fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
let constness = self.parse_constness();
let asyncness = self.parse_asyncness();
let unsafety = self.parse_unsafety();

44
src/librustc_parse/parser/ty.rs
View File

@ -127,16 +127,16 @@ fn parse_ty_common(
} else if self.eat_keyword(kw::Underscore) {
// A type to be inferred `_`
TyKind::Infer
} else if self.token_is_bare_fn_keyword() {
} else if self.check_fn_front_matter() {
// Function pointer type
self.parse_ty_bare_fn(Vec::new())?
self.parse_ty_bare_fn(lo, Vec::new())?
} else if self.check_keyword(kw::For) {
// Function pointer type or bound list (trait object type) starting with a poly-trait.
// `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
// `for<'lt> Trait1<'lt> + Trait2 + 'a`
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
if self.token_is_bare_fn_keyword() {
self.parse_ty_bare_fn(lifetime_defs)?
if self.check_fn_front_matter() {
self.parse_ty_bare_fn(lo, lifetime_defs)?
} else {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus();
@ -291,13 +291,6 @@ fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> {
Ok(TyKind::Typeof(expr))
}
/// Is the current token one of the keywords that signals a bare function type?
fn token_is_bare_fn_keyword(&mut self) -> bool {
self.check_keyword(kw::Fn)
|| self.check_keyword(kw::Unsafe)
|| self.check_keyword(kw::Extern)
}
/// Parses a function pointer type (`TyKind::BareFn`).
/// ```
/// [unsafe] [extern "ABI"] fn (S) -> T
@ -306,12 +299,31 @@ fn token_is_bare_fn_keyword(&mut self) -> bool {
/// | | | Return type
/// Function Style ABI Parameter types
/// ```
fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
let unsafety = self.parse_unsafety();
let ext = self.parse_extern()?;
self.expect_keyword(kw::Fn)?;
/// We actually parse `FnHeader FnDecl`, but we error on `const` and `async` qualifiers.
fn parse_ty_bare_fn(&mut self, lo: Span, params: Vec<GenericParam>) -> PResult<'a, TyKind> {
let ast::FnHeader { ext, unsafety, constness, asyncness } = self.parse_fn_front_matter()?;
let decl = self.parse_fn_decl(|_| false, AllowPlus::No)?;
Ok(TyKind::BareFn(P(BareFnTy { ext, unsafety, generic_params, decl })))
let whole_span = lo.to(self.prev_token.span);
if let ast::Const::Yes(span) = constness {
self.error_fn_ptr_bad_qualifier(whole_span, span, "const");
}
if let ast::Async::Yes { span, .. } = asyncness {
self.error_fn_ptr_bad_qualifier(whole_span, span, "async");
}
Ok(TyKind::BareFn(P(BareFnTy { ext, unsafety, generic_params: params, decl })))
}
/// Emit an error for the given bad function pointer qualifier.
fn error_fn_ptr_bad_qualifier(&self, span: Span, qual_span: Span, qual: &str) {
self.struct_span_err(span, &format!("an `fn` pointer type cannot be `{}`", qual))
.span_label(qual_span, format!("`{}` because of this", qual))
.span_suggestion_short(
qual_span,
&format!("remove the `{}` qualifier", qual),
String::new(),
Applicability::MaybeIncorrect,
)
.emit();
}
/// Parses an `impl B0 + ... + Bn` type.

2
src/test/ui/keyword/extern/keyword-extern-as-identifier-type.rs vendored
View File

@ -1,3 +1,3 @@
type A = extern::foo::bar; //~ ERROR expected `fn`, found `::`
type A = extern::foo::bar; //~ ERROR expected type, found keyword `extern`
fn main() {}

6
src/test/ui/keyword/extern/keyword-extern-as-identifier-type.stderr vendored
View File

@ -1,8 +1,8 @@
error: expected `fn`, found `::`
--> $DIR/keyword-extern-as-identifier-type.rs:1:16
error: expected type, found keyword `extern`
--> $DIR/keyword-extern-as-identifier-type.rs:1:10
|
LL | type A = extern::foo::bar;
| ^^ expected `fn`
| ^^^^^^ expected type
error: aborting due to previous error

2
src/test/ui/parser/issue-63116.stderr
View File

@ -12,7 +12,7 @@ error: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `;`
LL | impl W <s(f;Y(;]
| ^ expected one of 7 possible tokens
error: expected one of `!`, `&&`, `&`, `(`, `)`, `*`, `+`, `,`, `->`, `...`, `::`, `<`, `>`, `?`, `[`, `_`, `dyn`, `extern`, `fn`, `for`, `impl`, `unsafe`, lifetime, or path, found `;`
error: expected one of `!`, `&&`, `&`, `(`, `)`, `*`, `+`, `,`, `->`, `...`, `::`, `<`, `>`, `?`, `[`, `_`, `async`, `const`, `dyn`, `extern`, `fn`, `for`, `impl`, `unsafe`, lifetime, or path, found `;`
--> $DIR/issue-63116.rs:3:15
|
LL | impl W <s(f;Y(;]

25
src/test/ui/parser/recover-const-async-fn-ptr.rs Normal file
View File

@ -0,0 +1,25 @@
// edition:2018
type T0 = const fn(); //~ ERROR an `fn` pointer type cannot be `const`
type T1 = const extern "C" fn(); //~ ERROR an `fn` pointer type cannot be `const`
type T2 = const unsafe extern fn(); //~ ERROR an `fn` pointer type cannot be `const`
type T3 = async fn(); //~ ERROR an `fn` pointer type cannot be `async`
type T4 = async extern fn(); //~ ERROR an `fn` pointer type cannot be `async`
type T5 = async unsafe extern "C" fn(); //~ ERROR an `fn` pointer type cannot be `async`
type T6 = const async unsafe extern "C" fn();
//~^ ERROR an `fn` pointer type cannot be `const`
//~| ERROR an `fn` pointer type cannot be `async`
type FT0 = for<'a> const fn(); //~ ERROR an `fn` pointer type cannot be `const`
type FT1 = for<'a> const extern "C" fn(); //~ ERROR an `fn` pointer type cannot be `const`
type FT2 = for<'a> const unsafe extern fn(); //~ ERROR an `fn` pointer type cannot be `const`
type FT3 = for<'a> async fn(); //~ ERROR an `fn` pointer type cannot be `async`
type FT4 = for<'a> async extern fn(); //~ ERROR an `fn` pointer type cannot be `async`
type FT5 = for<'a> async unsafe extern "C" fn(); //~ ERROR an `fn` pointer type cannot be `async`
type FT6 = for<'a> const async unsafe extern "C" fn();
//~^ ERROR an `fn` pointer type cannot be `const`
//~| ERROR an `fn` pointer type cannot be `async`
fn main() {
let _recovery_witness: () = 0; //~ ERROR mismatched types
}

155
src/test/ui/parser/recover-const-async-fn-ptr.stderr Normal file
View File

@ -0,0 +1,155 @@
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:3:11
|
LL | type T0 = const fn();
| -----^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:4:11
|
LL | type T1 = const extern "C" fn();
| -----^^^^^^^^^^^^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:5:11
|
LL | type T2 = const unsafe extern fn();
| -----^^^^^^^^^^^^^^^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:6:11
|
LL | type T3 = async fn();
| -----^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:7:11
|
LL | type T4 = async extern fn();
| -----^^^^^^^^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:8:11
|
LL | type T5 = async unsafe extern "C" fn();
| -----^^^^^^^^^^^^^^^^^^^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:9:11
|
LL | type T6 = const async unsafe extern "C" fn();
| -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:9:11
|
LL | type T6 = const async unsafe extern "C" fn();
| ^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:13:12
|
LL | type FT0 = for<'a> const fn();
| ^^^^^^^^-----^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:14:12
|
LL | type FT1 = for<'a> const extern "C" fn();
| ^^^^^^^^-----^^^^^^^^^^^^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:15:12
|
LL | type FT2 = for<'a> const unsafe extern fn();
| ^^^^^^^^-----^^^^^^^^^^^^^^^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:16:12
|
LL | type FT3 = for<'a> async fn();
| ^^^^^^^^-----^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:17:12
|
LL | type FT4 = for<'a> async extern fn();
| ^^^^^^^^-----^^^^^^^^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:18:12
|
LL | type FT5 = for<'a> async unsafe extern "C" fn();
| ^^^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error: an `fn` pointer type cannot be `const`
--> $DIR/recover-const-async-fn-ptr.rs:19:12
|
LL | type FT6 = for<'a> const async unsafe extern "C" fn();
| ^^^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| `const` because of this
| help: remove the `const` qualifier
error: an `fn` pointer type cannot be `async`
--> $DIR/recover-const-async-fn-ptr.rs:19:12
|
LL | type FT6 = for<'a> const async unsafe extern "C" fn();
| ^^^^^^^^^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^
| |
| `async` because of this
| help: remove the `async` qualifier
error[E0308]: mismatched types
--> $DIR/recover-const-async-fn-ptr.rs:24:33
|
LL | let _recovery_witness: () = 0;
| -- ^ expected `()`, found integer
| |
| expected due to this
error: aborting due to 17 previous errors
For more information about this error, try `rustc --explain E0308`.