Rust: Handle functions in dependencies not having parameters

Author: paldepind

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

@@ -965,20 +965,25 @@ private module Cached {
 
   /** Holds if a method for `type` with the name `name` and the arity `arity` exists in `impl`. */
   pragma[nomagic]
-  private predicate methodCandidate(Type type, string name, int arity, Impl impl) {
+  private predicate methodCandidate(Type type, string name, Impl impl, Function f) {
     type = impl.(ImplTypeAbstraction).getSelfTy().(TypeReprMention).resolveType() and
-    exists(Function f |
-      f = impl.(ImplItemNode).getASuccessor(name) and
-      f.getParamList().hasSelfParam() and
-      arity = f.getParamList().getNumberOfParams()
-    )
+    f = impl.(ImplItemNode).getASuccessor(name)
   }
 
   private module IsInstantiationOfInput implements IsInstantiationOfSig<ReceiverExpr> {
     predicate potentialInstantiationOf(ReceiverExpr receiver, TypeAbstraction impl, TypeMention sub) {
-      methodCandidate(receiver.resolveTypeAt(TypePath::nil()), receiver.getField(),
-        receiver.getNumberOfArgs(), impl) and
-      sub = impl.(ImplTypeAbstraction).getSelfTy()
+      exists(Function method |
+        methodCandidate(receiver.resolveTypeAt(TypePath::nil()), receiver.getField(), impl, method) and
+        (
+          method.getParamList().getNumberOfParams() = receiver.getNumberOfArgs() and
+          method.getParamList().hasSelfParam()
+          or
+          // TODO: Once parameter lists for functions in dependencies are
+          // extracted correctly we should check arity for those as well.
+          not method.fromSource()
+        ) and
+        sub = impl.(ImplTypeAbstraction).getSelfTy()
+      )
     }
   }