Stop treating extern crate loading failures as fatal errors

compiler/rustc_metadata/src/creader.rs

@@ -9,6 +9,7 @@ use rustc_ast::{self as ast, *};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::svh::Svh;
 use rustc_data_structures::sync::Lrc;
+use rustc_errors::FatalError;
 use rustc_expand::base::SyntaxExtension;
 use rustc_hir::def_id::{CrateNum, LocalDefId, StableCrateId, LOCAL_CRATE};
 use rustc_hir::definitions::Definitions;
@@ -507,18 +508,31 @@ impl<'a> CrateLoader<'a> {
         }))
     }
 
-    fn resolve_crate<'b>(
+    fn resolve_crate_or_abort<'b>(
         &'b mut self,
         name: Symbol,
         span: Span,
         dep_kind: CrateDepKind,
     ) -> CrateNum {
+        self.resolve_crate(name, span, dep_kind).unwrap_or_else(|| FatalError.raise())
+    }
+
+    fn resolve_crate<'b>(
+        &'b mut self,
+        name: Symbol,
+        span: Span,
+        dep_kind: CrateDepKind,
+    ) -> 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)
-        })
+        self.maybe_resolve_crate(name, dep_kind, None).map_or_else(
+            |err| {
+                let missing_core =
+                    self.maybe_resolve_crate(sym::core, CrateDepKind::Explicit, None).is_err();
+                err.report(&self.sess, span, missing_core);
+                None
+            },
+            |cnum| Some(cnum),
+        )
     }
 
     fn maybe_resolve_crate<'b>(
@@ -751,7 +765,7 @@ impl<'a> CrateLoader<'a> {
         };
         info!("panic runtime not found -- loading {}", name);
 
-        let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit);
+        let cnum = self.resolve_crate_or_abort(name, DUMMY_SP, CrateDepKind::Implicit);
         let data = self.cstore.get_crate_data(cnum);
 
         // Sanity check the loaded crate to ensure it is indeed a panic runtime
@@ -791,7 +805,7 @@ impl<'a> CrateLoader<'a> {
             );
         }
 
-        let cnum = self.resolve_crate(name, DUMMY_SP, CrateDepKind::Implicit);
+        let cnum = self.resolve_crate_or_abort(name, DUMMY_SP, CrateDepKind::Implicit);
         let data = self.cstore.get_crate_data(cnum);
 
         // Sanity check the loaded crate to ensure it is indeed a profiler runtime
@@ -991,7 +1005,7 @@ 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 +1025,7 @@ 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 +1037,14 @@ 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);
+        let cnum = self.resolve_crate_or_abort(name, span, CrateDepKind::Explicit);
 
         self.update_extern_crate(
             cnum,

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, DiagnosticBuilder, 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 {
+    fn build_diag(self, sess: &Session, span: Span, missing_core: bool) -> DiagnosticBuilder<'_> {
+        match self {
             CrateError::NonAsciiName(crate_name) => sess.struct_span_err(
                 span,
                 &format!("cannot load a crate with a non-ascii name `{}`", crate_name),
@@ -1208,10 +1208,10 @@ impl CrateError {
                 "plugin `{}` only found in rlib format, but must be available in dylib format",
                 crate_name,
             ),
-        };
+        }
+    }
 
-        err.emit();
-        sess.abort_if_errors();
-        unreachable!();
+    crate fn report(self, sess: &Session, span: Span, missing_core: bool) {
+        self.build_diag(sess, span, missing_core).emit();
     }
 }

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -685,11 +685,8 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
             ItemKind::ExternCrate(orig_name) => {
                 self.build_reduced_graph_for_extern_crate(
                     orig_name,
-                    ident,
                     item,
                     local_def_id,
-                    sp,
-                    expansion,
                     vis,
                     parent,
                 );
@@ -833,14 +830,16 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
     fn build_reduced_graph_for_extern_crate(
         &mut self,
         orig_name: Option<Symbol>,
-        ident: Ident,
         item: &Item,
         local_def_id: LocalDefId,
-        sp: Span,
-        expansion: LocalExpnId,
         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 module = if orig_name.is_none() && ident.name == kw::SelfLower {
             self.r
                 .session
@@ -856,10 +855,32 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
         } 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())
+            match self.r.crate_loader.process_extern_crate(item, &self.r.definitions, local_def_id)
+            {
+                Some(crate_id) => {
+                    self.r.extern_crate_map.insert(local_def_id, crate_id);
+                    self.r.expect_module(crate_id.as_def_id())
+                }
+                _ => {
+                    let dummy_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(None),
+                        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(true),
+                    });
+                    self.r.import_dummy_binding(dummy_import);
+                    return;
+                }
+            }
         };
         let used = self.process_macro_use_imports(item, module);
         let binding =

compiler/rustc_resolve/src/imports.rs

@@ -600,8 +600,10 @@ impl<'a> Resolver<'a> {
 
     // Define a "dummy" resolution containing a Res::Err as a placeholder for a
     // failed resolution
-    fn import_dummy_binding(&mut self, import: &'a Import<'a>) {
-        if let ImportKind::Single { target, .. } = import.kind {
+    crate fn import_dummy_binding(&mut self, import: &'a Import<'a>) {
+        if let ImportKind::Single { target, .. } | ImportKind::ExternCrate { target, .. } =
+            import.kind
+        {
             let dummy_binding = self.dummy_binding;
             let dummy_binding = self.import(dummy_binding, import);
             self.per_ns(|this, ns| {

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 +1,8 @@
+// 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() {
+    foo::something();
+    bar::something();
+}

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

@@ -0,0 +1,15 @@
+error[E0463]: can't find crate for `bar`
+  --> $DIR/extern-crate-multiple-missing.rs:2:1
+   |
+LL | extern crate bar;
+   | ^^^^^^^^^^^^^^^^^ can't find crate
+
+error[E0463]: can't find crate for `foo`
+  --> $DIR/extern-crate-multiple-missing.rs:3:1
+   |
+LL | extern crate foo;
+   | ^^^^^^^^^^^^^^^^^ can't find crate
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0463`.

src/test/ui/issues/issue-37131.stderr

@@ -4,6 +4,8 @@ error[E0463]: can't find crate for `std`
    = help: consider downloading the target with `rustup target add thumbv6m-none-eabi`
    = 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/issues/issue-49851/compiler-builtins-error.rs

@@ -1,4 +1,5 @@
-//~ ERROR 1:1: 1:1: can't find crate for `core` [E0463]
+//~ ERROR can't find crate for `core`
+//~^ ERROR can't find crate for `compiler_builtins`
 
 // compile-flags: --target thumbv7em-none-eabihf
 // needs-llvm-components: arm
@@ -7,3 +8,6 @@
 #![no_std]
 
 extern crate cortex_m;
+//~^ ERROR can't find crate for `cortex_m`
+
+fn main() {}

src/test/ui/issues/issue-49851/compiler-builtins-error.stderr

@@ -4,6 +4,16 @@ error[E0463]: can't find crate for `core`
    = help: consider downloading the target with `rustup target add thumbv7em-none-eabihf`
    = help: consider building the standard library from source with `cargo build -Zbuild-std`
 
-error: aborting due to previous error
+error[E0463]: can't find crate for `compiler_builtins`
+
+error[E0463]: can't find crate for `cortex_m`
+  --> $DIR/compiler-builtins-error.rs:10:1
+   |
+LL | extern crate cortex_m;
+   | ^^^^^^^^^^^^^^^^^^^^^^ can't find crate
+
+error: requires `sized` lang_item
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0463`.