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Parse view type syntax, mark it as unstable

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This commit is contained in:
Sasha Pourcelot
2026-04-29 09:03:26 +00:00
parent d3992fac94
commit 77fb8d1d5c
4 changed files with 46 additions and 41 deletions
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compiler/rustc_ast_passes/src/feature_gate.rs
+1
View File
@@ -510,6 +510,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
gate_all!(try_blocks_heterogeneous, "`try bikeshed` expression is experimental");
gate_all!(unsafe_binders, "unsafe binder types are experimental");
gate_all!(unsafe_fields, "`unsafe` fields are experimental");
gate_all!(view_types, "view types are experimental");
gate_all!(where_clause_attrs, "attributes in `where` clause are unstable");
gate_all!(yeet_expr, "`do yeet` expression is experimental");
// tidy-alphabetical-end
compiler/rustc_parse/src/parser/ty.rs
+20 -1
View File
@@ -19,7 +19,7 @@ use crate::errors::{
NeedPlusAfterTraitObjectLifetime, NestedCVariadicType, ReturnTypesUseThinArrow,
};
use crate::parser::item::FrontMatterParsingMode;
use crate::parser::{FnContext, FnParseMode};
use crate::parser::{ExpTokenPair, FnContext, FnParseMode};
use crate::{exp, maybe_recover_from_interpolated_ty_qpath};
/// Signals whether parsing a type should allow `+`.
@@ -768,6 +768,25 @@ impl<'a> Parser<'a> {
self.bump_with((dyn_tok, dyn_tok_sp));
}
let ty = self.parse_ty_no_plus()?;
if self.token == TokenKind::Dot && self.look_ahead(1, |t| t.kind == TokenKind::OpenBrace) {
// & [mut] <type> . { <fields> }
// ^
// we are here
let view_start_span = self.token.span;
self.bump();
let fields = self
.parse_delim_comma_seq(
ExpTokenPair { tok: TokenKind::OpenBrace, token_type: TokenType::OpenBrace },
ExpTokenPair { tok: TokenKind::CloseBrace, token_type: TokenType::CloseBrace },
|p| p.parse_ident(),
)?
.0;
// FIXME(scrabsha): actually propagate field view in the AST.
let _ = fields;
let view_end_span = self.prev_token.span;
let span = view_start_span.to(view_end_span);
self.psess.gated_spans.gate(sym::view_types, span);
}
Ok(match pinned {
Pinnedness::Not => TyKind::Ref(opt_lifetime, MutTy { ty, mutbl }),
Pinnedness::Pinned => TyKind::PinnedRef(opt_lifetime, MutTy { ty, mutbl }),
tests/ui/feature-gates/feature-gate-view-types.rs
+3 -2
View File
@@ -1,11 +1,11 @@
//@ known-bug: #155938
struct Foo {
a: usize,
b: usize,
}
fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
//~^ ERROR view types are experimental
//~| ERROR view types are experimental
a.a += 1;
b.b += 1;
}
@@ -13,4 +13,5 @@ fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
fn main() {
let mut foo = Foo { a: 0, b: 0 };
bar(&mut foo, &mut foo);
//~^ ERROR cannot borrow `foo` as mutable more than once at a time
}
tests/ui/feature-gates/feature-gate-view-types.stderr
+22 -38
View File
@@ -1,49 +1,33 @@
error: expected parameter name, found `{`
--> $DIR/feature-gate-view-types.rs:8:20
error[E0658]: view types are experimental
--> $DIR/feature-gate-view-types.rs:6:19
|
LL | fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
| ^ expected parameter name
| ^^^^^^
|
= note: see issue #155938 <https://github.com/rust-lang/rust/issues/155938> for more information
= help: add `#![feature(view_types)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: expected one of `!`, `(`, `)`, `,`, `::`, or `<`, found `.`
--> $DIR/feature-gate-view-types.rs:8:19
error[E0658]: view types are experimental
--> $DIR/feature-gate-view-types.rs:6:38
|
LL | fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
| ^
| |
| expected one of `!`, `(`, `)`, `,`, `::`, or `<`
| help: missing `,`
error: expected parameter name, found `{`
--> $DIR/feature-gate-view-types.rs:8:39
| ^^^^^^
|
LL | fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
| ^ expected parameter name
= note: see issue #155938 <https://github.com/rust-lang/rust/issues/155938> for more information
= help: add `#![feature(view_types)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: expected one of `!`, `(`, `)`, `,`, `::`, or `<`, found `.`
--> $DIR/feature-gate-view-types.rs:8:38
|
LL | fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
| ^
| |
| expected one of `!`, `(`, `)`, `,`, `::`, or `<`
| help: missing `,`
error[E0061]: this function takes 4 arguments but 2 arguments were supplied
--> $DIR/feature-gate-view-types.rs:15:5
error[E0499]: cannot borrow `foo` as mutable more than once at a time
--> $DIR/feature-gate-view-types.rs:15:19
|
LL | bar(&mut foo, &mut foo);
| ^^^-------------------- two arguments are missing
|
note: function defined here
--> $DIR/feature-gate-view-types.rs:8:4
|
LL | fn bar(a: &mut Foo.{ a }, b: &mut Foo.{ b }) {
| ^^^ -----------------
help: provide the arguments
|
LL | bar(&mut foo, &mut foo, /* &mut Foo */, /* _ */);
| +++++++++++++++++++++++++
| --- -------- ^^^^^^^^ second mutable borrow occurs here
| | |
| | first mutable borrow occurs here
| first borrow later used by call
error: aborting due to 5 previous errors
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0061`.
Some errors have detailed explanations: E0499, E0658.
For more information about an error, try `rustc --explain E0499`.