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, 13 insertions, 11 deletions

diff --git a/crates/hir_def/src/find_path.rs b/crates/hir_def/src/find_path.rs
index ee52794aa..219ed4c07 100644
--- a/crates/hir_def/src/find_path.rs
+++ b/crates/hir_def/src/find_path.rs
@@ -682,9 +682,11 @@ pub struct S;
 //- /main.rs crate:main deps:std
 $0
 //- /std.rs crate:std
-pub mod prelude { pub struct S; }
-#[prelude_import]
-pub use prelude::*;
+pub mod prelude {
+    pub mod rust_2018 {
+        pub struct S;
+    }
+}
         "#,
             "S",
             "S",
@@ -700,11 +702,11 @@ pub use prelude::*;
 $0
 //- /std.rs crate:std
 pub mod prelude {
-    pub enum Option<T> { Some(T), None }
-    pub use Option::*;
+    pub mod rust_2018 {
+        pub enum Option<T> { Some(T), None }
+        pub use Option::*;
+    }
 }
-#[prelude_import]
-pub use prelude::*;
         "#;
         check_found_path(code, "None", "None", "None", "None");
         check_found_path(code, "Some", "Some", "Some", "Some");
@@ -1080,11 +1082,11 @@ fn f() {
 }
 //- /std.rs crate:std
 pub mod prelude {
-    pub enum Option { None }
-    pub use Option::*;
+    pub mod rust_2018 {
+        pub enum Option { None }
+        pub use Option::*;
+    }
 }
-#[prelude_import]
-pub use prelude::*;
         "#,
             "None",
             "None",