This condition seems to have an assignment (like a = b) instead of a comparison (like a == b).

Such code can be confusing and difficult to read and debug. Consider separating out the assignment and perform only a comparison within the expression.

Bad Practice

While this code will compile, it will also likely perform the wrong operation, since a will always be treated as being true.

if (a = true) {
    // ...
}

For other types, compilation will likely fail because in general, constructs such as if, for and while expect boolean expressions in their conditions, and will not accept other types.

Recommended

Change the assignment to a comparison.

if (a == true) {
    // ...
}