fix(resolve): not defined extern crate shadow_name

Author: bvanjoi

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -873,6 +873,11 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
                     let msg = "macro-expanded `extern crate` items cannot \
                                        shadow names passed with `--extern`";
                     self.r.tcx.sess.span_err(item.span, msg);
+                    // `return` is intended to discard this binding because it's an
+                    // unregistered ambiguity error which would result in a panic
+                    // caused by inconsistency `path_res`
+                    // more details: https://github.com/rust-lang/rust/pull/111761
+                    return;
                 }
             }
             let entry = self.r.extern_prelude.entry(ident.normalize_to_macros_2_0()).or_insert(

compiler/rustc_resolve/src/lib.rs

@@ -106,7 +106,7 @@ impl Determinacy {
 /// A specific scope in which a name can be looked up.
 /// This enum is currently used only for early resolution (imports and macros),
 /// but not for late resolution yet.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Debug)]
 enum Scope<'a> {
     DeriveHelpers(LocalExpnId),
     DeriveHelpersCompat,

tests/ui/imports/issue-109148.rs

@@ -0,0 +1,15 @@
+// edition: 2021
+
+// https://github.com/rust-lang/rust/pull/111761#issuecomment-1557777314
+macro_rules! m {
+    () => {
+        extern crate core as std;
+        //~^ ERROR macro-expanded `extern crate` items cannot shadow names passed with `--extern`
+    }
+}
+
+m!();
+
+use std::mem;
+
+fn main() {}

tests/ui/imports/issue-109148.stderr

@@ -0,0 +1,13 @@
+error: macro-expanded `extern crate` items cannot shadow names passed with `--extern`
+  --> $DIR/issue-109148.rs:6:9
+   |
+LL |         extern crate core as std;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | m!();
+   | ---- in this macro invocation
+   |
+   = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+