Fix #83045 by moving some crate loading verification code to a better place.

compiler/rustc_metadata/src/creader.rs

@@ -350,7 +350,6 @@ fn register_crate(
         let Library { source, metadata } = lib;
         let crate_root = metadata.get_root();
         let host_hash = host_lib.as_ref().map(|lib| lib.metadata.get_root().hash());
-        self.verify_no_symbol_conflicts(&crate_root)?;
 
         let private_dep =
             self.sess.opts.externs.get(&name.as_str()).map_or(false, |e| e.is_private_dep);
@@ -358,8 +357,6 @@ fn register_crate(
         // Claim this crate number and cache it
         let cnum = self.cstore.alloc_new_crate_num();
 
-        self.verify_no_stable_crate_id_hash_conflicts(&crate_root, cnum)?;
-
         info!(
             "register crate `{}` (cnum = {}. private_dep = {})",
             crate_root.name(),
@@ -394,6 +391,14 @@ fn register_crate(
             None
         };
 
+        // Perform some verification *after* resolve_crate_deps() above is
+        // known to have been successful. It seems that - in error cases - the
+        // cstore can be in a temporarily invalid state between cnum allocation
+        // and dependency resolution and the verification code would produce
+        // ICEs in that case (see #83045).
+        self.verify_no_symbol_conflicts(&crate_root)?;
+        self.verify_no_stable_crate_id_hash_conflicts(&crate_root, cnum)?;
+
         let crate_metadata = CrateMetadata::new(
             self.sess,
             metadata,

src/test/run-make-fulldeps/issue-83045/Makefile

+include ../../run-make-fulldeps/tools.mk
+
+# This test case creates a situation where the crate loader would run
+# into an ICE when confronted with an invalid setup where it cannot
+# find the dependency of a direct dependency.
+#
+# The test case makes sure that the compiler produces the expected
+# error message but does not ICE immediately after.
+#
+# See https://github.com/rust-lang/rust/issues/83045
+
+# This is a platform-independent issue, no need to waste time testing
+# everywhere.
+# only-x86_64
+# only-linux
+
+# NOTE: We use BARE_RUSTC below so that the compiler can't find liba.rlib
+#       If we used RUSTC the additional '-L TMPDIR' option would allow rustc to
+#       actually find the crate.
+#
+#       We check that we get the expected error message
+#       But that we do not get an ICE
+
+all:
+	$(RUSTC) --crate-name=a --crate-type=rlib a.rs --verbose
+	$(RUSTC) --crate-name=b --crate-type=rlib --extern a=$(TMPDIR)/liba.rlib b.rs --verbose
+	$(BARE_RUSTC) --out-dir $(TMPDIR) \
+	              --extern b=$(TMPDIR)/libb.rlib \
+				  --crate-type=rlib \
+				  --edition=2018 \
+				  c.rs 2>&1 | tee $(TMPDIR)/output.txt || exit 0
+	$(CGREP) E0463 < $(TMPDIR)/output.txt
+	$(CGREP) -v "internal compiler error" < $(TMPDIR)/output.txt

src/test/run-make-fulldeps/issue-83045/a.rs

+// empty on purpose

src/test/run-make-fulldeps/issue-83045/b.rs

+extern crate a;

src/test/run-make-fulldeps/issue-83045/c.rs

+use b as _;