Rust: Move the function pointer parameter exclusion into VariableImpl.qll.

rust/ql/lib/codeql/rust/elements/internal/VariableImpl.qll

@@ -87,7 +87,9 @@ module Impl {
     not name.charAt(0).isUppercase() and
     // exclude parameters from functions without a body as these are trait method declarations
     // without implementations
-    not exists(Function f | not f.hasBody() and f.getParamList().getAParam().getPat() = p)
+    not exists(Function f | not f.hasBody() and f.getParamList().getAParam().getPat() = p) and
+    // exclude parameters from function pointers as well, which also lack a body
+    not exists(FnPtrType fp | fp.getParamList().getParam(_).getPat() = p)
   }
 
   /** A variable. */

rust/ql/src/queries/unusedentities/UnusedVariable.qll

@@ -23,7 +23,4 @@ predicate isUnused(Variable v) {
 predicate isAllowableUnused(Variable v) {
   // in a macro expansion
   v.getPat().isInMacroExpansion()
-  or
-  // function pointer parameters
-  exists(FnPtrType fp | fp.getParamList().getParam(_).getPat() = v.getPat())
 }