If sym refers to a class member foo in class C,
returns a tree representing C.this.foo.
If sym refers to a local definition foo, returns
a tree representing foo.
Attributes
Note:
In both cases, the constructed tree should only
be spliced into the places where such accesses make sense.
For example, it is incorrect to have C.this.foo outside
the class body of C, or have foo outside the lexical
scope for the definition of foo.