This refactors SelfApplyExpr.getFunction() as MethodLookupExpr().getMethodRef().
This is simpler, because we are not hiding DeclRefExprs or reinventing hidden AST resolution.
In order to distinguish overloads of the constructor and for consistency
with other function calls, `ConstructorDecl` string representation uses
the name which includes parentheses and parameter labels.
For consistency also the destructor got the same change, which means
all `DestructorDecl`s will now show as `deinit()` rather than `deinit`.
This introduces a `MethodRefExpr` node synthesized out of
`DotSyntaxCallExpr` under the `LookupExpr` hierarchy. This means that
much like
```free_function(1, 2)```
is a `CallExpr` with `getFunction` giving a `DeclRefExpr`,
```foo.method(1, 2)```
is now a `CallExpr` with `getFunction` giving a `MethodRefExpr`.
`ApplyExpr::getStaticTarget` has been made work with it (as well as
`ConstructorRefCallExpr` which for the moment has been left where it
is), a new `MethodApplyExpr` has been introduced deriving from it,
and control and data flow libraries have adapted.
A small but was fixed in `qlgen` where the default constructor for DB
types was not correctly subtracting derived IPA types depending on the
order of definitions in `schema.yml`.
There are still some occurrences of `DotSyntaxCallExpr`, and as already
mentioned the other `SelfApply` class (`ConstructorRefCallExpr`) was
left alone. Their treatment is left for a future PR.
Now `TypeRepr` is a final class in the AST, which is more or less just
a type with a location in code.
As the frontend does not provide a direct way to get a type from a
type representation, this information must be provided when fetching
the label of a type repr.
This meant:
* removing the type repr field from `EnumIsCaseExpr`: this is a virtual
AST node introduced in place of some kinds of `IsEpxr`. The type
repr is still available from the `ConditionalCheckedCastExpr` wrapped
by this virtual node, and we will rebuild the original `IsExpr` with
the IPA layer.
* some logic to get the type of keypath roots has been added to
`KeyPathExpr`. This was done to keep the `TypeRepr` to `Type` relation
total in the DB, but goes against the design of a dumb extractor. The
logic could be moved to QL in the future
* in the control flow library, `TypeRepr` children are now ignored. As
far as I can tell, there is no runtime evaluation going on in
`TypeRepr`s, so it does not make much sense to have control flow
through them.
