`parameter_assignments` false negative for anonymous functions and constructors

[Giuspepe]

Describe the issue The lint parameter_assignments does not work with anonymous functions.

To Reproduce

void main(){
    // `parameter_assignments` works fine with named functions
    void foo(int i) {
      i = 42; // LINT: `parameter_assignments`
      print(i);
    }
    foo(0);

    // `parameter_assignments` does not work with anonymous functions
    (int i) {
      i = 42; // false negative: should yield lint but doesn't!
      print(i);
    }(0);
}

Expected behavior The lint parameter_assignments should work with anonymous functions as well.

[spkersten]

There's also no warning for constructors:

class Foo {
  Foo(int x) {
    x = 4;
  }
}