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]>

5 files changed, 97 insertions, 44 deletions

diff --git a/crates/hir_ty/src/tests/macros.rs b/crates/hir_ty/src/tests/macros.rs
index 7647bb08b..d14103aab 100644
--- a/crates/hir_ty/src/tests/macros.rs
+++ b/crates/hir_ty/src/tests/macros.rs
@@ -982,14 +982,18 @@ fn test() {
 }         //^ S
 
 //- /lib.rs crate:core
-#[prelude_import]
-use clone::*;
-mod clone {
-    trait Clone {
+pub mod prelude {
+    pub mod rust_2018 {
+        #[rustc_builtin_macro]
+        pub macro Clone {}
+        pub use crate::clone::Clone;
+    }
+}
+
+pub mod clone {
+    pub trait Clone {
         fn clone(&self) -> Self;
     }
-    #[rustc_builtin_macro]
-    macro Clone {}
 }
 "#,
     );
@@ -1001,14 +1005,22 @@ fn infer_derive_clone_in_core() {
         r#"
 //- /lib.rs crate:core
 #[prelude_import]
-use clone::*;
-mod clone {
-    trait Clone {
+use prelude::rust_2018::*;
+
+pub mod prelude {
+    pub mod rust_2018 {
+        #[rustc_builtin_macro]
+        pub macro Clone {}
+        pub use crate::clone::Clone;
+    }
+}
+
+pub mod clone {
+    pub trait Clone {
         fn clone(&self) -> Self;
     }
-    #[rustc_builtin_macro]
-    macro Clone {}
 }
+
 #[derive(Clone)]
 pub struct S;
 
@@ -1037,14 +1049,18 @@ fn test() {
 }
 
 //- /lib.rs crate:core
-#[prelude_import]
-use clone::*;
-mod clone {
-    trait Clone {
+pub mod prelude {
+    pub mod rust_2018 {
+        #[rustc_builtin_macro]
+        pub macro Clone {}
+        pub use crate::clone::Clone;
+    }
+}
+
+pub mod clone {
+    pub trait Clone {
         fn clone(&self) -> Self;
     }
-    #[rustc_builtin_macro]
-    macro Clone {}
 }
 "#,
     );
diff --git a/crates/hir_ty/src/tests/method_resolution.rs b/crates/hir_ty/src/tests/method_resolution.rs
index a4c132bc5..058eb9129 100644
--- a/crates/hir_ty/src/tests/method_resolution.rs
+++ b/crates/hir_ty/src/tests/method_resolution.rs
@@ -796,7 +796,7 @@ fn test() {
 fn method_resolution_trait_from_prelude() {
     check_types(
         r#"
-//- /main.rs crate:main deps:other_crate
+//- /main.rs crate:main deps:core
 struct S;
 impl Clone for S {}
 
@@ -805,12 +805,12 @@ fn test() {
           //^ S
 }
 
-//- /lib.rs crate:other_crate
-#[prelude_import] use foo::*;
-
-mod foo {
-    trait Clone {
-        fn clone(&self) -> Self;
+//- /lib.rs crate:core
+pub mod prelude {
+    pub mod rust_2018 {
+        pub trait Clone {
+            fn clone(&self) -> Self;
+        }
     }
 }
 "#,
diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index ad9edf11c..1019e783b 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -426,11 +426,12 @@ fn test() {
 
 //- /std.rs crate:std
 #[prelude_import]
-use prelude::*;
-
+use self::prelude::rust_2018::*;
 pub mod prelude {
-    pub use crate::iter::Iterator;
-    pub use crate::option::Option;
+    pub mod rust_2018 {
+        pub use crate::iter::Iterator;
+        pub use crate::option::Option;
+    }
 }
 
 pub mod iter {
diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index ac312981d..3418ed21e 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -2712,3 +2712,23 @@ fn main() {
         "#]],
     );
 }
+
+#[test]
+fn prelude_2015() {
+    check_types(
+        r#"
+//- /main.rs edition:2015 crate:main deps:core
+fn f() {
+    Rust;
+     //^ Rust
+}
+
+//- /core.rs crate:core
+pub mod prelude {
+    pub mod rust_2015 {
+        pub struct Rust;
+    }
+}
+    "#,
+    );
+}
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index 49add4ab9..588f0d1d4 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -20,11 +20,12 @@ fn test() {
 } //^ u64
 
 //- /core.rs crate:core
-#[prelude_import] use future::*;
-mod future {
-    #[lang = "future_trait"]
-    trait Future {
-        type Output;
+pub mod prelude {
+    pub mod rust_2018 {
+        #[lang = "future_trait"]
+        pub trait Future {
+            type Output;
+        }
     }
 }
 "#,
@@ -136,17 +137,15 @@ fn test() {
 } //^ i32
 
 //- /core.rs crate:core
-#[prelude_import] use ops::*;
-mod ops {
-    trait Try {
+pub mod ops {
+    pub trait Try {
         type Ok;
         type Error;
     }
 }
 
-#[prelude_import] use result::*;
-mod result {
-    enum Result<O, E> {
+pub mod result {
+    pub enum Result<O, E> {
         Ok(O),
         Err(E)
     }
@@ -156,6 +155,12 @@ mod result {
         type Error = E;
     }
 }
+
+pub mod prelude {
+    pub mod rust_2018 {
+        pub use crate::{result::*, ops::*};
+    }
+}
 "#,
     );
 }
@@ -190,8 +195,7 @@ mov convert {
     impl<T> From<T> for T {}
 }
 
-#[prelude_import] use result::*;
-mod result {
+pub mod result {
     use crate::convert::From;
     use crate::ops::{Try, FromResidual};
 
@@ -208,6 +212,12 @@ mod result {
 
     impl<T, E, F: From<E>> FromResidual<Result<Infallible, E>> for Result<T, F> {}
 }
+
+pub mod prelude {
+    pub mod rust_2018 {
+        pub use crate::result::*;
+    }
+}
 "#,
     );
 }
@@ -217,6 +227,7 @@ fn infer_for_loop() {
     check_types(
         r#"
 //- /main.rs crate:main deps:core,alloc
+#![no_std]
 use alloc::collections::Vec;
 
 fn test() {
@@ -228,14 +239,19 @@ fn test() {
 }
 
 //- /core.rs crate:core
-#[prelude_import] use iter::*;
-mod iter {
-    trait IntoIterator {
+pub mod iter {
+    pub trait IntoIterator {
         type Item;
     }
 }
+pub mod prelude {
+    pub mod rust_2018 {
+        pub use crate::iter::*;
+    }
+}
 
 //- /alloc.rs crate:alloc deps:core
+#![no_std]
 mod collections {
     struct Vec<T> {}
     impl<T> Vec<T> {