Rust: Fallback crate resolution

Author: hvitved

rust/ql/lib/codeql/rust/internal/PathResolution.qll

@@ -173,6 +173,7 @@ abstract class ItemNode extends Locatable {
     crateDefEdge(this, name, result, kind)
     or
     crateDependencyEdge(this, name, result) and
+    not declares(this, TTypeNamespace(), name) and
     kind.isInternal()
     or
     externCrateEdge(this, name, result) and
@@ -1138,6 +1139,11 @@ private class BuiltinSourceFile extends SourceFileItemNode {
 pragma[nomagic]
 private predicate crateDependencyEdge(SourceFileItemNode file, string name, CrateItemNode dep) {
   exists(CrateItemNode c | dep = c.(Crate).getDependency(name) | file = c.getASourceFile())
+  or
+  // All files _should_ belong to a crate, but for those where we cannot identify the crate,
+  // give access to all crates as a fallback.
+  not file = any(Crate c).getASourceFile() and
+  name = dep.getName()
 }
 
 private predicate useTreeDeclares(UseTree tree, string name) {