mirror of https://github.com/rust-lang/rust
43 lines
1.7 KiB
Rust
43 lines
1.7 KiB
Rust
#![feature(const_refs_to_cell)]
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use std::cell::*;
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struct SyncPtr<T> { x : *const T }
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unsafe impl<T> Sync for SyncPtr<T> {}
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// These pass the lifetime checks because of the "tail expression" / "outer scope" rule.
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// (This relies on `SyncPtr` being a curly brace struct.)
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// However, we intern the inner memory as read-only.
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// The resulting constant would pass all validation checks, so it is crucial that this gets rejected
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// by static const checks!
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static RAW_SYNC_S: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
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//~^ ERROR: cannot refer to interior mutable data
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const RAW_SYNC_C: SyncPtr<Cell<i32>> = SyncPtr { x: &Cell::new(42) };
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//~^ ERROR: cannot refer to interior mutable data
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// This one does not get promoted because of `Drop`, and then enters interesting codepaths because
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// as a value it has no interior mutability, but as a type it does. See
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// <https://github.com/rust-lang/rust/issues/121610>. Value-based reasoning for interior mutability
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// is questionable (https://github.com/rust-lang/unsafe-code-guidelines/issues/493) so for now we
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// reject this, though not with a great error message.
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pub enum JsValue {
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Undefined,
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Object(Cell<bool>),
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}
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impl Drop for JsValue {
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fn drop(&mut self) {}
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}
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const UNDEFINED: &JsValue = &JsValue::Undefined;
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//~^ WARNING: mutable pointer in final value of constant
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//~| WARNING: this was previously accepted by the compiler but is being phased out
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// In contrast, this one works since it is being promoted.
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const NONE: &'static Option<Cell<i32>> = &None;
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// Making it clear that this is promotion, not "outer scope".
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const NONE_EXPLICIT_PROMOTED: &'static Option<Cell<i32>> = {
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let x = &None;
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x
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};
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fn main() {}
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