mirror of https://github.com/rust-lang/rust
74 lines
1.8 KiB
Rust
74 lines
1.8 KiB
Rust
// Test that we properly detect the cycle amongst the traits
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// here and report an error.
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use std::panic::RefUnwindSafe;
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trait Database {
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type Storage;
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}
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trait HasQueryGroup {}
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trait Query<DB> {
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type Data;
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}
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trait SourceDatabase {
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fn parse(&self) {
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loop {}
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}
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}
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struct ParseQuery;
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struct RootDatabase {
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_runtime: Runtime<RootDatabase>,
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}
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struct Runtime<DB: Database> {
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_storage: Box<DB::Storage>,
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}
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struct SalsaStorage {
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_parse: <ParseQuery as Query<RootDatabase>>::Data,
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//~^ ERROR overflow
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}
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impl Database for RootDatabase {
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type Storage = SalsaStorage;
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//~^ ERROR overflow
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}
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impl HasQueryGroup for RootDatabase {}
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impl<DB> Query<DB> for ParseQuery
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where
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DB: SourceDatabase,
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DB: Database,
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{
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type Data = RootDatabase;
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}
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impl<T> SourceDatabase for T
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where
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T: RefUnwindSafe,
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T: HasQueryGroup,
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{
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}
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pub(crate) fn goto_implementation(db: &RootDatabase) -> u32 {
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// This is not satisfied:
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//
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// - `RootDatabase: SourceDatabase`
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// - requires `RootDatabase: RefUnwindSafe` + `RootDatabase: HasQueryGroup`
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// - `RootDatabase: RefUnwindSafe`
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// - requires `Runtime<RootDatabase>: RefUnwindSafe`
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// - `Runtime<RootDatabase>: RefUnwindSafe`
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// - requires `DB::Storage: RefUnwindSafe` (`SalsaStorage: RefUnwindSafe`)
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// - `SalsaStorage: RefUnwindSafe`
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// - requires `<ParseQuery as Query<RootDatabase>>::Data: RefUnwindSafe`,
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// which means `ParseQuery: Query<RootDatabase>`
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// - `ParseQuery: Query<RootDatabase>`
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// - requires `RootDatabase: SourceDatabase`,
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// - `RootDatabase: SourceDatabase` is already on the stack, so we have a
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// cycle with non-coinductive participants
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//
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// we used to fail to report an error here because we got the
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// caching wrong.
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SourceDatabase::parse(db);
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22
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}
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fn main() {}
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