Delphi – E2012 Type of expression must be BOOLEAN

Posted by AbundantCode

When an expression is used as a condition, it must be of the Boolean type to produce this error message. This is true for the if, while, and repeat statements’ controlling expressions, as well as the expression that controls a conditional breakpoint.

program Produce;
var
  P: Pointer;
begin
  if P then
    Writeln('P <> nil');
end.

A pointer variable was used as the condition of an if statement in this case by a C++ writer.

program Solve;
var
  P: Pointer;
begin
  if P <> nil then
    Writeln('P <> nil');
end.

In this scenario, you must be more explicit in Delphi.

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