diff --git a/src/libsyntax/feature_gate/active.rs b/src/libsyntax/feature_gate/active.rs index 47ee41f0adc16..20a77fa37cf6a 100644 --- a/src/libsyntax/feature_gate/active.rs +++ b/src/libsyntax/feature_gate/active.rs @@ -519,6 +519,9 @@ declare_features! ( /// Allows the use of or-patterns (e.g., `0 | 1`). (active, or_patterns, "1.38.0", Some(54883), None), + /// Allows the definition of `const extern fn` and `const unsafe extern fn`. + (active, const_extern_fn, "1.40.0", Some(64926), None), + // ------------------------------------------------------------------------- // feature-group-end: actual feature gates // ------------------------------------------------------------------------- diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs index d7fc74955bbbd..9e40b1a26ac1a 100644 --- a/src/libsyntax/feature_gate/check.rs +++ b/src/libsyntax/feature_gate/check.rs @@ -821,6 +821,7 @@ pub fn check_crate(krate: &ast::Crate, gate_all!(async_closure, "async closures are unstable"); gate_all!(yields, generators, "yield syntax is experimental"); gate_all!(or_patterns, "or-patterns syntax is experimental"); + gate_all!(const_extern_fn, "`const extern fn` definitions are unstable"); visit::walk_crate(&mut visitor, krate); } diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs index fa4c10431228a..1518da23b096f 100644 --- a/src/libsyntax/parse/mod.rs +++ b/src/libsyntax/parse/mod.rs @@ -57,6 +57,8 @@ pub struct GatedSpans { pub yields: Lock>, /// Spans collected for gating `or_patterns`, e.g. `Some(Foo | Bar)`. pub or_patterns: Lock>, + /// Spans collected for gating `const_extern_fn`, e.g. `const extern fn foo`. + pub const_extern_fn: Lock>, } /// Info about a parsing session. diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs index 95f84d5cb3314..6b0b60bfe477d 100644 --- a/src/libsyntax/parse/parser.rs +++ b/src/libsyntax/parse/parser.rs @@ -1486,6 +1486,15 @@ impl<'a> Parser<'a> { Ok(()) } + /// Parses `extern` followed by an optional ABI string, or nothing. + fn parse_extern_abi(&mut self) -> PResult<'a, Abi> { + if self.eat_keyword(kw::Extern) { + Ok(self.parse_opt_abi()?.unwrap_or(Abi::C)) + } else { + Ok(Abi::Rust) + } + } + /// Parses a string as an ABI spec on an extern type or module. Consumes /// the `extern` keyword, if one is found. fn parse_opt_abi(&mut self) -> PResult<'a, Option> { diff --git a/src/libsyntax/parse/parser/item.rs b/src/libsyntax/parse/parser/item.rs index c00a5807d52c5..2ac0352764fa0 100644 --- a/src/libsyntax/parse/parser/item.rs +++ b/src/libsyntax/parse/parser/item.rs @@ -149,17 +149,24 @@ impl<'a> Parser<'a> { } if self.eat_keyword(kw::Const) { let const_span = self.prev_span; - if self.check_keyword(kw::Fn) - || (self.check_keyword(kw::Unsafe) - && self.is_keyword_ahead(1, &[kw::Fn])) { + if [kw::Fn, kw::Unsafe, kw::Extern].iter().any(|k| self.check_keyword(*k)) { // CONST FUNCTION ITEM + let unsafety = self.parse_unsafety(); - self.bump(); + + if self.check_keyword(kw::Extern) { + self.sess.gated_spans.const_extern_fn.borrow_mut().push( + lo.to(self.token.span) + ); + } + let abi = self.parse_extern_abi()?; + self.bump(); // 'fn' + let header = FnHeader { unsafety, asyncness: respan(const_span, IsAsync::NotAsync), constness: respan(const_span, Constness::Const), - abi: Abi::Rust, + abi, }; return self.parse_item_fn(lo, visibility, attrs, header); } @@ -257,11 +264,7 @@ impl<'a> Parser<'a> { self.bump(); // `unsafe` // `{` is also expected after `unsafe`; in case of error, include it in the diagnostic. self.check(&token::OpenDelim(token::Brace)); - let abi = if self.eat_keyword(kw::Extern) { - self.parse_opt_abi()?.unwrap_or(Abi::C) - } else { - Abi::Rust - }; + let abi = self.parse_extern_abi()?; self.expect_keyword(kw::Fn)?; let fn_span = self.prev_span; let header = FnHeader { @@ -834,11 +837,7 @@ impl<'a> Parser<'a> { let (constness, unsafety, abi) = if is_const_fn { (respan(const_span, Constness::Const), unsafety, Abi::Rust) } else { - let abi = if self.eat_keyword(kw::Extern) { - self.parse_opt_abi()?.unwrap_or(Abi::C) - } else { - Abi::Rust - }; + let abi = self.parse_extern_abi()?; (respan(self.prev_span, Constness::NotConst), unsafety, abi) }; if !self.eat_keyword(kw::Fn) { @@ -1278,14 +1277,30 @@ impl<'a> Parser<'a> { // Treat `const` as `static` for error recovery, but don't add it to expected tokens. if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) { if self.token.is_keyword(kw::Const) { - self.diagnostic() - .struct_span_err(self.token.span, "extern items cannot be `const`") - .span_suggestion( + let mut err = self + .struct_span_err(self.token.span, "extern items cannot be `const`"); + + + // The user wrote 'const fn' + if self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe]) { + err.emit(); + // Consume `const` + self.bump(); + // Consume `unsafe` if present, since `extern` blocks + // don't allow it. This will leave behind a plain 'fn' + self.eat_keyword(kw::Unsafe); + // Treat 'const fn` as a plain `fn` for error recovery purposes. + // We've already emitted an error, so compilation is guaranteed + // to fail + return Ok(self.parse_item_foreign_fn(visibility, lo, attrs, extern_sp)?); + } + err.span_suggestion( self.token.span, "try using a static value", "static".to_owned(), Applicability::MachineApplicable - ).emit(); + ); + err.emit(); } self.bump(); // `static` or `const` return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?); diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs index 1769135e7f21a..38e55cb5c5dfe 100644 --- a/src/libsyntax_pos/symbol.rs +++ b/src/libsyntax_pos/symbol.rs @@ -196,6 +196,7 @@ symbols! { console, const_compare_raw_pointers, const_constructor, + const_extern_fn, const_fn, const_fn_union, const_generics, diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-call-extern-fn.rs b/src/test/ui/consts/const-extern-fn/const-extern-fn-call-extern-fn.rs new file mode 100644 index 0000000000000..7c6a574a2110f --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-call-extern-fn.rs @@ -0,0 +1,23 @@ +#![feature(const_extern_fn)] + +extern "C" { + fn regular_in_block(); +} + +const extern fn bar() { + unsafe { + regular_in_block(); + //~^ ERROR: cannot call functions with `"C"` abi in `min_const_fn` + } +} + +extern fn regular() {} + +const extern fn foo() { + unsafe { + regular(); + //~^ ERROR: cannot call functions with `"C"` abi in `min_const_fn` + } +} + +fn main() {} diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-call-extern-fn.stderr b/src/test/ui/consts/const-extern-fn/const-extern-fn-call-extern-fn.stderr new file mode 100644 index 0000000000000..d8bdf0a57cf66 --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-call-extern-fn.stderr @@ -0,0 +1,21 @@ +error[E0723]: cannot call functions with `"C"` abi in `min_const_fn` + --> $DIR/const-extern-fn-call-extern-fn.rs:9:9 + | +LL | regular_in_block(); + | ^^^^^^^^^^^^^^^^^^ + | + = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 + = help: add `#![feature(const_fn)]` to the crate attributes to enable + +error[E0723]: cannot call functions with `"C"` abi in `min_const_fn` + --> $DIR/const-extern-fn-call-extern-fn.rs:18:9 + | +LL | regular(); + | ^^^^^^^^^ + | + = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 + = help: add `#![feature(const_fn)]` to the crate attributes to enable + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0723`. diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs new file mode 100644 index 0000000000000..5619811768801 --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.rs @@ -0,0 +1,13 @@ +#![feature(const_extern_fn)] + +const extern fn unsize(x: &[u8; 3]) -> &[u8] { x } +//~^ ERROR unsizing casts are not allowed in const fn +const unsafe extern "C" fn closure() -> fn() { || {} } +//~^ ERROR function pointers in const fn are unstable +const unsafe extern fn use_float() { 1.0 + 1.0; } +//~^ ERROR only int, `bool` and `char` operations are stable in const fn +const extern "C" fn ptr_cast(val: *const u8) { val as usize; } +//~^ ERROR casting pointers to ints is unstable in const fn + + +fn main() {} diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr new file mode 100644 index 0000000000000..0ab1ddd8d5225 --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-min-const-fn.stderr @@ -0,0 +1,39 @@ +error[E0723]: unsizing casts are not allowed in const fn + --> $DIR/const-extern-fn-min-const-fn.rs:3:48 + | +LL | const extern fn unsize(x: &[u8; 3]) -> &[u8] { x } + | ^ + | + = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 + = help: add `#![feature(const_fn)]` to the crate attributes to enable + +error[E0723]: function pointers in const fn are unstable + --> $DIR/const-extern-fn-min-const-fn.rs:5:41 + | +LL | const unsafe extern "C" fn closure() -> fn() { || {} } + | ^^^^ + | + = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 + = help: add `#![feature(const_fn)]` to the crate attributes to enable + +error[E0723]: only int, `bool` and `char` operations are stable in const fn + --> $DIR/const-extern-fn-min-const-fn.rs:7:38 + | +LL | const unsafe extern fn use_float() { 1.0 + 1.0; } + | ^^^^^^^^^ + | + = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 + = help: add `#![feature(const_fn)]` to the crate attributes to enable + +error[E0723]: casting pointers to ints is unstable in const fn + --> $DIR/const-extern-fn-min-const-fn.rs:9:48 + | +LL | const extern "C" fn ptr_cast(val: *const u8) { val as usize; } + | ^^^^^^^^^^^^ + | + = note: for more information, see issue https://github.com/rust-lang/rust/issues/57563 + = help: add `#![feature(const_fn)]` to the crate attributes to enable + +error: aborting due to 4 previous errors + +For more information about this error, try `rustc --explain E0723`. diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.rs b/src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.rs new file mode 100644 index 0000000000000..cab175bbfa818 --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.rs @@ -0,0 +1,10 @@ +#![feature(const_extern_fn)] + +const unsafe extern fn foo() -> usize { 5 } + +fn main() { + let a: [u8; foo()]; + //~^ ERROR call to unsafe function is unsafe and requires unsafe function or block + foo(); + //~^ ERROR call to unsafe function is unsafe and requires unsafe function or block +} diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.stderr b/src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.stderr new file mode 100644 index 0000000000000..5196b8ee0a21d --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn-requires-unsafe.stderr @@ -0,0 +1,19 @@ +error[E0133]: call to unsafe function is unsafe and requires unsafe function or block + --> $DIR/const-extern-fn-requires-unsafe.rs:8:5 + | +LL | foo(); + | ^^^^^ call to unsafe function + | + = note: consult the function's documentation for information on how to avoid undefined behavior + +error[E0133]: call to unsafe function is unsafe and requires unsafe function or block + --> $DIR/const-extern-fn-requires-unsafe.rs:6:17 + | +LL | let a: [u8; foo()]; + | ^^^^^ call to unsafe function + | + = note: consult the function's documentation for information on how to avoid undefined behavior + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0133`. diff --git a/src/test/ui/consts/const-extern-fn/const-extern-fn.rs b/src/test/ui/consts/const-extern-fn/const-extern-fn.rs new file mode 100644 index 0000000000000..1dc0f83cadf7d --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/const-extern-fn.rs @@ -0,0 +1,35 @@ +// run-pass +#![feature(const_extern_fn)] + +const extern fn foo1(val: u8) -> u8 { + val + 1 +} + +const extern "C" fn foo2(val: u8) -> u8 { + val + 1 +} + +const unsafe extern fn bar1(val: bool) -> bool { + !val +} + +const unsafe extern "C" fn bar2(val: bool) -> bool { + !val +} + + +fn main() { + let a: [u8; foo1(25) as usize] = [0; 26]; + let b: [u8; foo2(25) as usize] = [0; 26]; + assert_eq!(a, b); + + let bar1_res = unsafe { bar1(false) }; + let bar2_res = unsafe { bar2(false) }; + assert!(bar1_res); + assert_eq!(bar1_res, bar2_res); + + let _foo1_cast: extern fn(u8) -> u8 = foo1; + let _foo2_cast: extern fn(u8) -> u8 = foo2; + let _bar1_cast: unsafe extern fn(bool) -> bool = bar1; + let _bar2_cast: unsafe extern fn(bool) -> bool = bar2; +} diff --git a/src/test/ui/consts/const-extern-fn/feature-gate-const_extern_fn.rs b/src/test/ui/consts/const-extern-fn/feature-gate-const_extern_fn.rs new file mode 100644 index 0000000000000..d39f2c1fe277e --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/feature-gate-const_extern_fn.rs @@ -0,0 +1,12 @@ +// Check that `const extern fn` and `const unsafe extern fn` are feature-gated. + +#[cfg(FALSE)] const extern fn foo1() {} //~ ERROR `const extern fn` definitions are unstable +#[cfg(FALSE)] const extern "C" fn foo2() {} //~ ERROR `const extern fn` definitions are unstable +#[cfg(FALSE)] const extern "Rust" fn foo3() {} //~ ERROR `const extern fn` definitions are unstable +#[cfg(FALSE)] const unsafe extern fn bar1() {} //~ ERROR `const extern fn` definitions are unstable +#[cfg(FALSE)] const unsafe extern "C" fn bar2() {} +//~^ ERROR `const extern fn` definitions are unstable +#[cfg(FALSE)] const unsafe extern "Rust" fn bar3() {} +//~^ ERROR `const extern fn` definitions are unstable + +fn main() {} diff --git a/src/test/ui/consts/const-extern-fn/feature-gate-const_extern_fn.stderr b/src/test/ui/consts/const-extern-fn/feature-gate-const_extern_fn.stderr new file mode 100644 index 0000000000000..f138620ffefba --- /dev/null +++ b/src/test/ui/consts/const-extern-fn/feature-gate-const_extern_fn.stderr @@ -0,0 +1,57 @@ +error[E0658]: `const extern fn` definitions are unstable + --> $DIR/feature-gate-const_extern_fn.rs:3:15 + | +LL | #[cfg(FALSE)] const extern fn foo1() {} + | ^^^^^^^^^^^^ + | + = note: for more information, see https://github.com/rust-lang/rust/issues/64926 + = help: add `#![feature(const_extern_fn)]` to the crate attributes to enable + +error[E0658]: `const extern fn` definitions are unstable + --> $DIR/feature-gate-const_extern_fn.rs:4:15 + | +LL | #[cfg(FALSE)] const extern "C" fn foo2() {} + | ^^^^^^^^^^^^ + | + = note: for more information, see https://github.com/rust-lang/rust/issues/64926 + = help: add `#![feature(const_extern_fn)]` to the crate attributes to enable + +error[E0658]: `const extern fn` definitions are unstable + --> $DIR/feature-gate-const_extern_fn.rs:5:15 + | +LL | #[cfg(FALSE)] const extern "Rust" fn foo3() {} + | ^^^^^^^^^^^^ + | + = note: for more information, see https://github.com/rust-lang/rust/issues/64926 + = help: add `#![feature(const_extern_fn)]` to the crate attributes to enable + +error[E0658]: `const extern fn` definitions are unstable + --> $DIR/feature-gate-const_extern_fn.rs:6:15 + | +LL | #[cfg(FALSE)] const unsafe extern fn bar1() {} + | ^^^^^^^^^^^^^^^^^^^ + | + = note: for more information, see https://github.com/rust-lang/rust/issues/64926 + = help: add `#![feature(const_extern_fn)]` to the crate attributes to enable + +error[E0658]: `const extern fn` definitions are unstable + --> $DIR/feature-gate-const_extern_fn.rs:7:15 + | +LL | #[cfg(FALSE)] const unsafe extern "C" fn bar2() {} + | ^^^^^^^^^^^^^^^^^^^ + | + = note: for more information, see https://github.com/rust-lang/rust/issues/64926 + = help: add `#![feature(const_extern_fn)]` to the crate attributes to enable + +error[E0658]: `const extern fn` definitions are unstable + --> $DIR/feature-gate-const_extern_fn.rs:9:15 + | +LL | #[cfg(FALSE)] const unsafe extern "Rust" fn bar3() {} + | ^^^^^^^^^^^^^^^^^^^ + | + = note: for more information, see https://github.com/rust-lang/rust/issues/64926 + = help: add `#![feature(const_extern_fn)]` to the crate attributes to enable + +error: aborting due to 6 previous errors + +For more information about this error, try `rustc --explain E0658`. diff --git a/src/test/ui/parser/no-const-fn-in-extern-block.rs b/src/test/ui/parser/no-const-fn-in-extern-block.rs new file mode 100644 index 0000000000000..29f26389ded18 --- /dev/null +++ b/src/test/ui/parser/no-const-fn-in-extern-block.rs @@ -0,0 +1,8 @@ +extern { + const fn foo(); + //~^ ERROR extern items cannot be `const` + const unsafe fn bar(); + //~^ ERROR extern items cannot be `const` +} + +fn main() {} diff --git a/src/test/ui/parser/no-const-fn-in-extern-block.stderr b/src/test/ui/parser/no-const-fn-in-extern-block.stderr new file mode 100644 index 0000000000000..5b4663a702f06 --- /dev/null +++ b/src/test/ui/parser/no-const-fn-in-extern-block.stderr @@ -0,0 +1,14 @@ +error: extern items cannot be `const` + --> $DIR/no-const-fn-in-extern-block.rs:2:5 + | +LL | const fn foo(); + | ^^^^^ + +error: extern items cannot be `const` + --> $DIR/no-const-fn-in-extern-block.rs:4:5 + | +LL | const unsafe fn bar(); + | ^^^^^ + +error: aborting due to 2 previous errors +