Rollup merge of rust-lang#145322 - LorrensP-2158466:early-prelude-processing, r=petrochenkov

Resolve the prelude import in `build_reduced_graph`

This pr tries to resolve the prelude import at the `build_reduced_graph` stage.
Part of batched import resolution in rust-lang#145108 (cherry picked commit) and maybe needed for rust-lang#139493.

r? petrochenkov

Author: Zalathar

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -493,9 +493,6 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     });
                 }
             }
-            // We don't add prelude imports to the globs since they only affect lexical scopes,
-            // which are not relevant to import resolution.
-            ImportKind::Glob { is_prelude: true, .. } => {}
             ImportKind::Glob { .. } => current_module.globs.borrow_mut().push(import),
             _ => unreachable!(),
         }
@@ -658,13 +655,19 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 self.add_import(module_path, kind, use_tree.span, item, root_span, item.id, vis);
             }
             ast::UseTreeKind::Glob => {
-                let kind = ImportKind::Glob {
-                    is_prelude: ast::attr::contains_name(&item.attrs, sym::prelude_import),
-                    max_vis: Cell::new(None),
-                    id,
-                };
-
-                self.add_import(prefix, kind, use_tree.span, item, root_span, item.id, vis);
+                if !ast::attr::contains_name(&item.attrs, sym::prelude_import) {
+                    let kind = ImportKind::Glob { max_vis: Cell::new(None), id };
+                    self.add_import(prefix, kind, use_tree.span, item, root_span, item.id, vis);
+                } else {
+                    // Resolve the prelude import early.
+                    let path_res =
+                        self.r.cm().maybe_resolve_path(&prefix, None, &self.parent_scope, None);
+                    if let PathResult::Module(ModuleOrUniformRoot::Module(module)) = path_res {
+                        self.r.prelude = Some(module);
+                    } else {
+                        self.r.dcx().span_err(use_tree.span, "cannot resolve a prelude import");
+                    }
+                }
             }
             ast::UseTreeKind::Nested { ref items, .. } => {
                 // Ensure there is at most one `self` in the list

compiler/rustc_resolve/src/imports.rs

@@ -87,7 +87,6 @@ pub(crate) enum ImportKind<'ra> {
         id: NodeId,
     },
     Glob {
-        is_prelude: bool,
         // The visibility of the greatest re-export.
         // n.b. `max_vis` is only used in `finalize_import` to check for re-export errors.
         max_vis: Cell<Option<Visibility>>,
@@ -125,12 +124,9 @@ impl<'ra> std::fmt::Debug for ImportKind<'ra> {
                 .field("nested", nested)
                 .field("id", id)
                 .finish(),
-            Glob { is_prelude, max_vis, id } => f
-                .debug_struct("Glob")
-                .field("is_prelude", is_prelude)
-                .field("max_vis", max_vis)
-                .field("id", id)
-                .finish(),
+            Glob { max_vis, id } => {
+                f.debug_struct("Glob").field("max_vis", max_vis).field("id", id).finish()
+            }
             ExternCrate { source, target, id } => f
                 .debug_struct("ExternCrate")
                 .field("source", source)
@@ -1073,7 +1069,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             ImportKind::Single { source, target, ref bindings, type_ns_only, id, .. } => {
                 (source, target, bindings, type_ns_only, id)
             }
-            ImportKind::Glob { is_prelude, ref max_vis, id } => {
+            ImportKind::Glob { ref max_vis, id } => {
                 if import.module_path.len() <= 1 {
                     // HACK(eddyb) `lint_if_path_starts_with_module` needs at least
                     // 2 segments, so the `resolve_path` above won't trigger it.
@@ -1096,8 +1092,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         module: None,
                     });
                 }
-                if !is_prelude
-                    && let Some(max_vis) = max_vis.get()
+                if let Some(max_vis) = max_vis.get()
                     && !max_vis.is_at_least(import.vis, self.tcx)
                 {
                     let def_id = self.local_def_id(id);
@@ -1485,7 +1480,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
     fn resolve_glob_import(&mut self, import: Import<'ra>) {
         // This function is only called for glob imports.
-        let ImportKind::Glob { id, is_prelude, .. } = import.kind else { unreachable!() };
+        let ImportKind::Glob { id, .. } = import.kind else { unreachable!() };
 
         let ModuleOrUniformRoot::Module(module) = import.imported_module.get().unwrap() else {
             self.dcx().emit_err(CannotGlobImportAllCrates { span: import.span });
@@ -1504,9 +1499,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         if module == import.parent_scope.module {
             return;
-        } else if is_prelude {
-            self.prelude = Some(module);
-            return;
         }
 
         // Add to module's glob_importers

library/core/src/lib.rs

@@ -208,6 +208,10 @@
 #[allow(unused_extern_crates)]
 extern crate self as core;
 
+/* The core prelude, not as all-encompassing as the std prelude */
+// The compiler expects the prelude definition to be defined before it's use statement.
+pub mod prelude;
+
 #[prelude_import]
 #[allow(unused)]
 use prelude::rust_2024::*;
@@ -293,10 +297,6 @@ pub mod f64;
 #[macro_use]
 pub mod num;
 
-/* The core prelude, not as all-encompassing as the std prelude */
-
-pub mod prelude;
-
 /* Core modules for ownership management */
 
 pub mod hint;

library/std/src/lib.rs

@@ -428,6 +428,10 @@
 //
 #![default_lib_allocator]
 
+// The Rust prelude
+// The compiler expects the prelude definition to be defined before it's use statement.
+pub mod prelude;
+
 // Explicitly import the prelude. The compiler uses this same unstable attribute
 // to import the prelude implicitly when building crates that depend on std.
 #[prelude_import]
@@ -483,9 +487,6 @@ mod macros;
 #[macro_use]
 pub mod rt;
 
-// The Rust prelude
-pub mod prelude;
-
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::any;
 #[stable(feature = "core_array", since = "1.35.0")]

tests/ui/extern-flag/empty-extern-arg.rs

@@ -1,4 +1,5 @@
 //~ ERROR extern location for std does not exist
+//~^ ERROR cannot resolve a prelude import
 //@ compile-flags: --extern std=
 //@ needs-unwind since it affects the error output
 //@ ignore-emscripten missing eh_catch_typeinfo lang item

tests/ui/extern-flag/empty-extern-arg.stderr

@@ -1,11 +1,13 @@
 error: extern location for std does not exist: 
 
+error: cannot resolve a prelude import
+
 error: `#[panic_handler]` function required, but not found
 
 error: unwinding panics are not supported without std
    |
    = help: using nightly cargo, use -Zbuild-std with panic="abort" to avoid unwinding
    = note: since the core library is usually precompiled with panic="unwind", rebuilding your crate with panic="abort" may not be enough to fix the problem
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 

tests/ui/proc-macro/derive-helper-legacy-spurious.rs

@@ -6,7 +6,7 @@
 extern crate test_macros;
 
 #[derive(Empty)]
-#[empty_helper] //~ ERROR cannot find attribute `empty_helper` in this scope
+#[empty_helper]
 struct Foo {}
 
 fn main() {}

tests/ui/proc-macro/derive-helper-legacy-spurious.stderr

@@ -4,11 +4,5 @@ error: cannot find attribute `dummy` in this scope
 LL | #![dummy]
    |    ^^^^^
 
-error: cannot find attribute `empty_helper` in this scope
-  --> $DIR/derive-helper-legacy-spurious.rs:9:3
-   |
-LL | #[empty_helper]
-   |   ^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 

tests/ui/resolve/inner-attr-prelude-macro.rs

@@ -0,0 +1,11 @@
+//@ check-pass
+//! This test checks that macro names resolved from the libstd prelude
+//! still work even if there's a crate-level custom inner attribute.
+
+#![feature(custom_inner_attributes)]
+
+#![rustfmt::skip]
+
+fn main() {
+    let _ = todo!();
+}

tests/ui/unpretty/exhaustive.expanded.stdout

@@ -34,9 +34,6 @@ extern crate std;
 #[prelude_import]
 use std::prelude::rust_2024::*;
 
-#[prelude_import]
-use self::prelude::*;
-
 mod prelude {
     pub use std::prelude::rust_2024::*;
 
@@ -47,6 +44,9 @@ mod prelude {
     }
 }
 
+#[prelude_import]
+use self::prelude::*;
+
 mod attributes {
     //! inner single-line doc comment
     /*!