Rust: Fixes based on PR review

Author: paldepind

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

@@ -99,7 +99,7 @@ module Impl {
      *
      * This is either 1 for prefix operations, or 2 for binary operations.
      */
-    final int getNumberOfOperands() { result = count(this.getAnOperand()) }
+    final int getNumberOfOperands() { result = strictcount(this.getAnOperand()) }
 
     /** Gets an operand of this operation. */
     Expr getAnOperand() { result = this.getOperand(_) }

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

@@ -691,6 +691,8 @@ private module CallExprBaseMatchingInput implements MatchingInputSig {
   }
 
   private class OperationAccess extends Access instanceof Operation {
+    OperationAccess() { super.isOverloaded(_, _) }
+
     override Type getTypeArgument(TypeArgumentPosition apos, TypePath path) {
       // The syntax for operators does not allow type arguments.
       none()