Merge #9097

9097: feat: Implement per-edition preludes r=jonas-schievink a=jonas-schievink

Part of https://github.com/rust-analyzer/rust-analyzer/issues/9056

Our previous implementation was incorrect (presumably because of the misleading comment in libstd [here](https://github.com/rust-lang/rust/blob/a7890c7952bdc9445eb6c63dc671fa7a1ab0260d/library/std/src/lib.rs#L339-L343)). `#[prelude_import]` does not define the prelude, it can only override the implicit prelude for the current crate.

This PR fixes that, which also makes the prelude imports in `rustc_span` work. Closes https://github.com/rust-analyzer/rust-analyzer/issues/8815.

bors r+

Co-authored-by: Jonas Schievink <[email protected]>

1 files changed, 12 insertions, 10 deletions

diff --git a/crates/ide_db/src/helpers/famous_defs_fixture.rs b/crates/ide_db/src/helpers/famous_defs_fixture.rs
index 29ae12dcf..312851966 100644
--- a/crates/ide_db/src/helpers/famous_defs_fixture.rs
+++ b/crates/ide_db/src/helpers/famous_defs_fixture.rs
@@ -128,17 +128,19 @@ pub mod option {
 }
 
 pub mod prelude {
-    pub use crate::{
-        cmp::Ord,
-        convert::{From, Into},
-        default::Default,
-        iter::{IntoIterator, Iterator},
-        ops::{Fn, FnMut, FnOnce},
-        option::Option::{self, *},
-    };
+    pub mod rust_2018 {
+        pub use crate::{
+            cmp::Ord,
+            convert::{From, Into},
+            default::Default,
+            iter::{IntoIterator, Iterator},
+            ops::{Fn, FnMut, FnOnce},
+            option::Option::{self, *},
+        };
+    }
 }
 #[prelude_import]
-pub use prelude::*;
+pub use prelude::rust_2018::*;
 //- /libstd.rs crate:std deps:core
 //! Signatures of traits, types and functions from the std lib for use in tests.
 
@@ -148,4 +150,4 @@ mod return_keyword {}
 /// Docs for prim_str
 mod prim_str {}
 
-pub use core::ops;
\ No newline at end of file
+pub use core::ops;