Access Violation When First Matcher is Not Defined

[IgorKaplya]

An access violation occurs in the TBehavior.Match function when the first matcher is not defined. This issue arises because the MatchWithMatchers function attempts to access an undefined matcher, leading to a runtime error.

Steps to Reproduce:

1. Create a mock object using TMock<IInterfaceToTest>.
2. Set up the mock to return a value when specific parameters are matched.
3. Call the method with the specified parameters.

Example Code:

procedure TExample_MatchersTests.Match_parameter_partial();
var
  mockCredit: TMock<IInterfaceToTest>;
begin
  mockCredit := TMock<IInterfaceToTest>.Create;

  mockCredit.Setup.WillReturn(6).When.TakesTwoParams(1, It(1).IsEqualTo<boolean>(true));

  Assert.AreEqual(6, mockCredit.Instance.TakesTwoParams(1, true));
end;

Presumed Bug Location:
The bug is likely in the TBehavior.Match function, specifically within the MatchWithMatchers function:

function TBehavior.Match(const Args: TArray<TValue>): Boolean;

  function MatchWithMatchers: Boolean;
  var
    i : integer;
  begin
    result := False;
    for i := 0 to High(FMatchers) do
    begin
      // Access violation when FMatchers[i] is nil
      if not FMatchers[i].Match(Args[i+1]) then
        exit;
    end;
    result := True;
  end;

Expected Behavior:
The function should handle cases where matchers are not defined without causing an access violation.

Actual Behavior:
An access violation occurs when the first matcher is not defined.

Environment:

• Delphi version: 11.3
• Operating System: Windows11

[IgorKaplya]

I beg your pardon for the hustle :)
This issue is a coincidence caused by an incorrect guard exception in the TProxy<T>.DoInvoke method:

procedure TProxy<T>.DoInvoke(Method: TRttiMethod; const Args: TArray<TValue>; out Result: TValue);
...
// Ooops... Someone just defined only the last arguments matcher, others are nils.
if Length(matchers) > 0 then
  if Length(matchers) < Length(Args) - 1 then
    raise EMockSetupException.Create('Setup called with Matchers but on all parameters : ' + Method.Name); // should say NOT on all parameters

I would suggest

• either to fix the Guard,
• or make this awesome tool better and allow people to match only some arguments.