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.
By explicitly marking children in the `schema.yml` file, an internal
`getAChild` predicate is implemented, that is in turn used in `AstNode`
to implement `getParent`.
This is yet to be used in the control flow library to replace the
hand-rolled implementation.
A further, more complex step is to use the same information to fully
generate the core implementation of `PrintAst` (including the
accessor string). This will be done later.
The `parent` tests use the same swift code as the extractor tests, and
this is currently enforced by `sync-files.py`. Notice that `qltest.sh`
had to be modified to deal with multiple files, which was not working
yet.
This transfers the current state of `StmtVisitor` in the PoC, plus some
changes required for the update to swift 5.6.
Also `getLabel` in `SwiftDispatcher` got renamed to `createLabel`, and
is now correctly outputting the label assignment to the trap file.
