Rollup merge of rust-lang#91045 - mjptree:issue-90702-fix, r=petrochenkov

Issue 90702 fix: Stop treating some crate loading failures as fatal errors

Surface mulitple `extern crate` resolution errors at a time.

This is achieved by creating a dummy crate, instead of aborting directly after the resolution error. The `ExternCrateError` has been added to allow propagating the resolution error from `rustc_metadata` crate to the `rustc_resolve` with a minimal public surface. The `import_extern_crate` function is a block that was factored out from `build_reduced_graph_for_item` for better organization. The only added functionality made to it where the added error handling in the `process_extern_crate` call. The remaining bits in this function are the same as before.

Resolves rust-lang#90702

r? `@petrochenkov`

Author: matthiaskrgr

compiler/rustc_metadata/src/creader.rs

@@ -512,13 +512,17 @@ impl<'a> CrateLoader<'a> {
         name: Symbol,
         span: Span,
         dep_kind: CrateDepKind,
-    ) -> CrateNum {
+    ) -> Option<CrateNum> {
         self.used_extern_options.insert(name);
-        self.maybe_resolve_crate(name, dep_kind, None).unwrap_or_else(|err| {
-            let missing_core =
-                self.maybe_resolve_crate(sym::core, CrateDepKind::Explicit, None).is_err();
-            err.report(&self.sess, span, missing_core)
-        })
+        match self.maybe_resolve_crate(name, dep_kind, None) {
+            Ok(cnum) => Some(cnum),
+            Err(err) => {
+                let missing_core =
+                    self.maybe_resolve_crate(sym::core, CrateDepKind::Explicit, None).is_err();
+                err.report(&self.sess, span, missing_core);
+                None
+            }
+        }
     }
 
     fn maybe_resolve_crate<'b>(
@@ -751,7 +755,7 @@ impl<'a> CrateLoader<'a> {
         };
         info!("panic runtime not found -- loading {}", name);
 
-        let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit);
+        let Some(cnum) = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit) else { return; };
         let data = self.cstore.get_crate_data(cnum);
 
         // Sanity check the loaded crate to ensure it is indeed a panic runtime
@@ -791,7 +795,7 @@ impl<'a> CrateLoader<'a> {
             );
         }
 
-        let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit);
+        let Some(cnum) = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit) else { return; };
         let data = self.cstore.get_crate_data(cnum);
 
         // Sanity check the loaded crate to ensure it is indeed a profiler runtime
@@ -991,7 +995,7 @@ impl<'a> CrateLoader<'a> {
         item: &ast::Item,
         definitions: &Definitions,
         def_id: LocalDefId,
-    ) -> CrateNum {
+    ) -> Option<CrateNum> {
         match item.kind {
             ast::ItemKind::ExternCrate(orig_name) => {
                 debug!(
@@ -1011,7 +1015,7 @@ impl<'a> CrateLoader<'a> {
                     CrateDepKind::Explicit
                 };
 
-                let cnum = self.resolve_crate(name, item.span, dep_kind);
+                let cnum = self.resolve_crate(name, item.span, dep_kind)?;
 
                 let path_len = definitions.def_path(def_id).data.len();
                 self.update_extern_crate(
@@ -1023,14 +1027,14 @@ impl<'a> CrateLoader<'a> {
                         dependency_of: LOCAL_CRATE,
                     },
                 );
-                cnum
+                Some(cnum)
             }
             _ => bug!(),
         }
     }
 
-    pub fn process_path_extern(&mut self, name: Symbol, span: Span) -> CrateNum {
-        let cnum = self.resolve_crate(name, span, CrateDepKind::Explicit);
+    pub fn process_path_extern(&mut self, name: Symbol, span: Span) -> Option<CrateNum> {
+        let cnum = self.resolve_crate(name, span, CrateDepKind::Explicit)?;
 
         self.update_extern_crate(
             cnum,
@@ -1043,7 +1047,7 @@ impl<'a> CrateLoader<'a> {
             },
         );
 
-        cnum
+        Some(cnum)
     }
 
     pub fn maybe_process_path_extern(&mut self, name: Symbol) -> Option<CrateNum> {

compiler/rustc_metadata/src/locator.rs

@@ -220,7 +220,7 @@ use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::owning_ref::OwningRef;
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::MetadataRef;
-use rustc_errors::struct_span_err;
+use rustc_errors::{struct_span_err, FatalError};
 use rustc_session::config::{self, CrateType};
 use rustc_session::cstore::{CrateSource, MetadataLoader};
 use rustc_session::filesearch::{FileDoesntMatch, FileMatches, FileSearch};
@@ -814,11 +814,11 @@ pub fn find_plugin_registrar(
     span: Span,
     name: Symbol,
 ) -> PathBuf {
-    match find_plugin_registrar_impl(sess, metadata_loader, name) {
-        Ok(res) => res,
+    find_plugin_registrar_impl(sess, metadata_loader, name).unwrap_or_else(|err| {
         // `core` is always available if we got as far as loading plugins.
-        Err(err) => err.report(sess, span, false),
-    }
+        err.report(sess, span, false);
+        FatalError.raise()
+    })
 }
 
 fn find_plugin_registrar_impl<'a>(
@@ -931,8 +931,8 @@ impl fmt::Display for MetadataError<'_> {
 }
 
 impl CrateError {
-    crate fn report(self, sess: &Session, span: Span, missing_core: bool) -> ! {
-        let mut err = match self {
+    crate fn report(self, sess: &Session, span: Span, missing_core: bool) {
+        let mut diag = match self {
             CrateError::NonAsciiName(crate_name) => sess.struct_span_err(
                 span,
                 &format!("cannot load a crate with a non-ascii name `{}`", crate_name),
@@ -1210,8 +1210,6 @@ impl CrateError {
             ),
         };
 
-        err.emit();
-        sess.abort_if_errors();
-        unreachable!();
+        diag.emit();
     }
 }

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -683,75 +683,13 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             }
 
             ItemKind::ExternCrate(orig_name) => {
-                let module = if orig_name.is_none() && ident.name == kw::SelfLower {
-                    self.r
-                        .session
-                        .struct_span_err(item.span, "`extern crate self;` requires renaming")
-                        .span_suggestion(
-                            item.span,
-                            "try",
-                            "extern crate self as name;".into(),
-                            Applicability::HasPlaceholders,
-                        )
-                        .emit();
-                    return;
-                } else if orig_name == Some(kw::SelfLower) {
-                    self.r.graph_root
-                } else {
-                    let crate_id = self.r.crate_loader.process_extern_crate(
-                        item,
-                        &self.r.definitions,
-                        local_def_id,
-                    );
-                    self.r.extern_crate_map.insert(local_def_id, crate_id);
-                    self.r.expect_module(crate_id.as_def_id())
-                };
-
-                let used = self.process_macro_use_imports(item, module);
-                let binding =
-                    (module, ty::Visibility::Public, sp, expansion).to_name_binding(self.r.arenas);
-                let import = self.r.arenas.alloc_import(Import {
-                    kind: ImportKind::ExternCrate { source: orig_name, target: ident },
-                    root_id: item.id,
-                    id: item.id,
-                    parent_scope: self.parent_scope,
-                    imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
-                    has_attributes: !item.attrs.is_empty(),
-                    use_span_with_attributes: item.span_with_attributes(),
-                    use_span: item.span,
-                    root_span: item.span,
-                    span: item.span,
-                    module_path: Vec::new(),
-                    vis: Cell::new(vis),
-                    used: Cell::new(used),
-                });
-                self.r.potentially_unused_imports.push(import);
-                let imported_binding = self.r.import(binding, import);
-                if ptr::eq(parent, self.r.graph_root) {
-                    if let Some(entry) = self.r.extern_prelude.get(&ident.normalize_to_macros_2_0())
-                    {
-                        if expansion != LocalExpnId::ROOT
-                            && orig_name.is_some()
-                            && entry.extern_crate_item.is_none()
-                        {
-                            let msg = "macro-expanded `extern crate` items cannot \
-                                       shadow names passed with `--extern`";
-                            self.r.session.span_err(item.span, msg);
-                        }
-                    }
-                    let entry =
-                        self.r.extern_prelude.entry(ident.normalize_to_macros_2_0()).or_insert(
-                            ExternPreludeEntry {
-                                extern_crate_item: None,
-                                introduced_by_item: true,
-                            },
-                        );
-                    entry.extern_crate_item = Some(imported_binding);
-                    if orig_name.is_some() {
-                        entry.introduced_by_item = true;
-                    }
-                }
-                self.r.define(parent, ident, TypeNS, imported_binding);
+                self.build_reduced_graph_for_extern_crate(
+                    orig_name,
+                    item,
+                    local_def_id,
+                    vis,
+                    parent,
+                );
             }
 
             ItemKind::Mod(..) => {
@@ -889,6 +827,87 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         }
     }
 
+    fn build_reduced_graph_for_extern_crate(
+        &mut self,
+        orig_name: Option<Symbol>,
+        item: &Item,
+        local_def_id: LocalDefId,
+        vis: ty::Visibility,
+        parent: Module<'a>,
+    ) {
+        let ident = item.ident;
+        let sp = item.span;
+        let parent_scope = self.parent_scope;
+        let expansion = parent_scope.expansion;
+
+        let (used, module, binding) = if orig_name.is_none() && ident.name == kw::SelfLower {
+            self.r
+                .session
+                .struct_span_err(item.span, "`extern crate self;` requires renaming")
+                .span_suggestion(
+                    item.span,
+                    "rename the `self` crate to be able to import it",
+                    "extern crate self as name;".into(),
+                    Applicability::HasPlaceholders,
+                )
+                .emit();
+            return;
+        } else if orig_name == Some(kw::SelfLower) {
+            Some(self.r.graph_root)
+        } else {
+            self.r.crate_loader.process_extern_crate(item, &self.r.definitions, local_def_id).map(
+                |crate_id| {
+                    self.r.extern_crate_map.insert(local_def_id, crate_id);
+                    self.r.expect_module(crate_id.as_def_id())
+                },
+            )
+        }
+        .map(|module| {
+            let used = self.process_macro_use_imports(item, module);
+            let binding =
+                (module, ty::Visibility::Public, sp, expansion).to_name_binding(self.r.arenas);
+            (used, Some(ModuleOrUniformRoot::Module(module)), binding)
+        })
+        .unwrap_or((true, None, self.r.dummy_binding));
+        let import = self.r.arenas.alloc_import(Import {
+            kind: ImportKind::ExternCrate { source: orig_name, target: ident },
+            root_id: item.id,
+            id: item.id,
+            parent_scope: self.parent_scope,
+            imported_module: Cell::new(module),
+            has_attributes: !item.attrs.is_empty(),
+            use_span_with_attributes: item.span_with_attributes(),
+            use_span: item.span,
+            root_span: item.span,
+            span: item.span,
+            module_path: Vec::new(),
+            vis: Cell::new(vis),
+            used: Cell::new(used),
+        });
+        self.r.potentially_unused_imports.push(import);
+        let imported_binding = self.r.import(binding, import);
+        if ptr::eq(parent, self.r.graph_root) {
+            if let Some(entry) = self.r.extern_prelude.get(&ident.normalize_to_macros_2_0()) {
+                if expansion != LocalExpnId::ROOT
+                    && orig_name.is_some()
+                    && entry.extern_crate_item.is_none()
+                {
+                    let msg = "macro-expanded `extern crate` items cannot \
+                                       shadow names passed with `--extern`";
+                    self.r.session.span_err(item.span, msg);
+                }
+            }
+            let entry = self.r.extern_prelude.entry(ident.normalize_to_macros_2_0()).or_insert(
+                ExternPreludeEntry { extern_crate_item: None, introduced_by_item: true },
+            );
+            entry.extern_crate_item = Some(imported_binding);
+            if orig_name.is_some() {
+                entry.introduced_by_item = true;
+            }
+        }
+        self.r.define(parent, ident, TypeNS, imported_binding);
+    }
+
     /// Constructs the reduced graph for one foreign item.
     fn build_reduced_graph_for_foreign_item(&mut self, item: &ForeignItem) {
         let local_def_id = self.r.local_def_id(item.id);

compiler/rustc_resolve/src/lib.rs

@@ -3288,7 +3288,9 @@ impl<'a> Resolver<'a> {
                 Some(binding)
             } else {
                 let crate_id = if !speculative {
-                    self.crate_loader.process_path_extern(ident.name, ident.span)
+                    let Some(crate_id) =
+                        self.crate_loader.process_path_extern(ident.name, ident.span) else { return Some(self.dummy_binding); };
+                    crate_id
                 } else {
                     self.crate_loader.maybe_process_path_extern(ident.name)?
                 };

src/test/ui/crate-loading/invalid-rlib.rs

@@ -6,3 +6,5 @@
 #![no_std]
 use ::foo; //~ ERROR invalid metadata files for crate `foo`
 //~| NOTE failed to mmap file
+//~^^ ERROR invalid metadata files for crate `foo`
+//~| NOTE failed to mmap file

src/test/ui/crate-loading/invalid-rlib.stderr

@@ -6,6 +6,14 @@ LL | use ::foo;
    |
    = note: failed to mmap file 'auxiliary/libfoo.rlib'
 
-error: aborting due to previous error
+error[E0786]: found invalid metadata files for crate `foo`
+  --> $DIR/invalid-rlib.rs:7:7
+   |
+LL | use ::foo;
+   |       ^^^
+   |
+   = note: failed to mmap file 'auxiliary/libfoo.rlib'
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0786`.

src/test/ui/crate-loading/missing-std.rs

@@ -1,6 +1,7 @@
 // compile-flags: --target x86_64-unknown-uefi
 // needs-llvm-components: x86
 // rustc-env:CARGO=/usr/bin/cargo
+#![feature(no_core)]
 #![no_core]
 extern crate core;
 //~^ ERROR can't find crate for `core`

src/test/ui/crate-loading/missing-std.stderr

@@ -1,5 +1,5 @@
 error[E0463]: can't find crate for `core`
-  --> $DIR/missing-std.rs:5:1
+  --> $DIR/missing-std.rs:6:1
    |
 LL | extern crate core;
    | ^^^^^^^^^^^^^^^^^^ can't find crate
@@ -8,6 +8,8 @@ LL | extern crate core;
    = help: consider downloading the target with `rustup target add x86_64-unknown-uefi`
    = help: consider building the standard library from source with `cargo build -Zbuild-std`
 
-error: aborting due to previous error
+error: requires `sized` lang_item
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0463`.

src/test/ui/extern-flag/empty-extern-arg.stderr

@@ -1,4 +1,8 @@
 error: extern location for std does not exist: 
 
-error: aborting due to previous error
+error: language item required, but not found: `eh_personality`
+
+error: `#[panic_handler]` function required, but not found
+
+error: aborting due to 3 previous errors
 

src/test/ui/extern/extern-crate-multiple-missing.rs

@@ -0,0 +1,10 @@
+// If multiple `extern crate` resolutions fail each of them should produce an error
+extern crate bar; //~ ERROR can't find crate for `bar`
+extern crate foo; //~ ERROR can't find crate for `foo`
+
+fn main() {
+    // If the crate name introduced by `extern crate` failed to resolve then subsequent
+    // derived paths do not emit additional errors
+    foo::something();
+    bar::something();
+}