Mixin template, "no identifier for declarator"

[SimonN via Digitalmars-d-learn]

Hi,

I'd like to generate several very similar class methods with a 
mixin template.
The mixin template shall take alias parameters, so that different 
methods can
bind it to different fields. Reduced problem case:
    class A {
        int myField;

        mixin template fieldSetter(alias whatField)
        {
            whatField = newVal;
        }

        int setMyField(in int newVal)
        {
            mixin fieldSetter!myField;
        }
    }

Compiler error message, DMD64 v2.068.2, line 6 is "whatField = 
newVal;":

    (6): Error: no identifier for declarator whatField
    (6): Error: declaration expected, not '='

I believe I'm following as closely as appropriate what's 
described at
http://dlang.org/template-mixin.html under "Mixins can 
parameterize symbols
using alias parameters".

Why does it error out on whatField, apparently deeming it to be a 
type?

Can I get this done with mixin templates? (I'd like to avoid 
string mixins,
the workaround with them got a little ugly.)

-- Simon