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make const_generics_defaults use the unstable syntax mechanism

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This is important to not accidentally stabilize the parsing of the syntax while it still is experimental and not formally accepted
This commit is contained in:
Rémy Rakic 2020-12-31 18:32:06 +01:00
parent 1fc3c4c16d
commit 942b7ce2c1
9 changed files with 45 additions and 35 deletions
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14
compiler/rustc_ast_passes/src/ast_validation.rs
View file

@ -1166,20 +1166,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
}
}
}
if !self.session.features_untracked().const_generics_defaults {
if let GenericParamKind::Const { default: Some(ref default), .. } = param.kind {
let mut err = self.err_handler().struct_span_err(
default.value.span,
"default values for const generic parameters are unstable",
);
err.help(
"add `#![feature(const_generics_defaults)]` \
to the crate attributes to enable",
);
err.emit();
break;
}
}
}
validate_generic_param_order(

4
compiler/rustc_ast_passes/src/feature_gate.rs
View file

@ -619,6 +619,10 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
extended_key_value_attributes,
"arbitrary expressions in key-value attributes are unstable"
);
gate_all!(
const_generics_defaults,
"default values for const generic parameters are experimental"
);
if sess.parse_sess.span_diagnostic.err_count() == 0 {
// Errors for `destructuring_assignment` can get quite noisy, especially where `_` is
// involved, so we only emit errors where there are no other parsing errors.

17
compiler/rustc_parse/src/parser/generics.rs
View file

@ -5,7 +5,7 @@ use rustc_ast::{
self as ast, Attribute, GenericBounds, GenericParam, GenericParamKind, WhereClause,
};
use rustc_errors::PResult;
use rustc_span::symbol::kw;
use rustc_span::symbol::{kw, sym};
impl<'a> Parser<'a> {
/// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
@ -56,8 +56,19 @@ impl<'a> Parser<'a> {
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
// Parse optional const generics default value.
let default = if self.eat(&token::Eq) { Some(self.parse_const_arg()?) } else { None };
// Parse optional const generics default value, taking care of feature gating the spans
// with the unstable syntax mechanism.
let default = if self.eat(&token::Eq) {
// The gated span goes from the `=` to the end of the const argument that follows (and
// which could be a block expression).
let start = self.prev_token.span;
let const_arg = self.parse_const_arg()?;
let span = start.to(const_arg.value.span);
self.sess.gated_spans.gate(sym::const_generics_defaults, span);
Some(const_arg)
} else {
None
};
Ok(GenericParam {
ident,

2
src/test/ui/const-generics/min_const_generics/default_function_param.rs
View file

@ -1,4 +1,4 @@
fn foo<const SIZE: usize = 5>() {}
//~^ ERROR default values for const generic parameters are unstable
//~^ ERROR default values for const generic parameters are experimental
fn main() {}

8
src/test/ui/const-generics/min_const_generics/default_function_param.stderr
View file

@ -1,10 +1,12 @@
error: default values for const generic parameters are unstable
--> $DIR/default_function_param.rs:1:28
error[E0658]: default values for const generic parameters are experimental
--> $DIR/default_function_param.rs:1:26
|
LL | fn foo<const SIZE: usize = 5>() {}
| ^
| ^^^
|
= note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
= help: add `#![feature(const_generics_defaults)]` to the crate attributes to enable
error: aborting due to previous error
For more information about this error, try `rustc --explain E0658`.

2
src/test/ui/const-generics/min_const_generics/default_trait_param.rs
View file

@ -1,4 +1,4 @@
trait Foo<const KIND: bool = true> {}
//~^ ERROR default values for const generic parameters are unstable
//~^ ERROR default values for const generic parameters are experimental
fn main() {}

8
src/test/ui/const-generics/min_const_generics/default_trait_param.stderr
View file

@ -1,10 +1,12 @@
error: default values for const generic parameters are unstable
--> $DIR/default_trait_param.rs:1:30
error[E0658]: default values for const generic parameters are experimental
--> $DIR/default_trait_param.rs:1:28
|
LL | trait Foo<const KIND: bool = true> {}
| ^^^^
| ^^^^^^
|
= note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
= help: add `#![feature(const_generics_defaults)]` to the crate attributes to enable
error: aborting due to previous error
For more information about this error, try `rustc --explain E0658`.

8
src/test/ui/feature-gates/feature-gate-const_generics_defaults.rs
View file

@ -1,7 +1,9 @@
#[cfg(FALSE)]
struct A<const N: usize = 3>;
//~^ ERROR default values for const generic parameters are unstable
//~^ ERROR default values for const generic parameters are experimental
fn foo<const N: u8 = 6>() {}
//~^ ERROR default values for const generic parameters are unstable
#[cfg(FALSE)]
fn foo<const B: bool = false>() {}
//~^ ERROR default values for const generic parameters are experimental
fn main() {}

17
src/test/ui/feature-gates/feature-gate-const_generics_defaults.stderr
View file

@ -1,18 +1,21 @@
error: default values for const generic parameters are unstable
--> $DIR/feature-gate-const_generics_defaults.rs:1:27
error[E0658]: default values for const generic parameters are experimental
--> $DIR/feature-gate-const_generics_defaults.rs:2:25
|
LL | struct A<const N: usize = 3>;
| ^
| ^^^
|
= note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
= help: add `#![feature(const_generics_defaults)]` to the crate attributes to enable
error: default values for const generic parameters are unstable
--> $DIR/feature-gate-const_generics_defaults.rs:4:22
error[E0658]: default values for const generic parameters are experimental
--> $DIR/feature-gate-const_generics_defaults.rs:6:22
|
LL | fn foo<const N: u8 = 6>() {}
| ^
LL | fn foo<const B: bool = false>() {}
| ^^^^^^^
|
= note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
= help: add `#![feature(const_generics_defaults)]` to the crate attributes to enable
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0658`.