|
|
* Default arguments are always retained on the <init> method (i.e.,
the class' constructor). Therefore, when the <init> parameters are
created, we need to use `duplicateAndKeepPositions` to make sure that
if a default argument is present, its opaque position is retained as
well. This is necessary because when parameter accessors (i.e.,
`fieldDefs`) are created, all default arguments are discared ( as you
can see in the code, the right-hand-side of a `field` is always an
`EmptyTree`) - see changes in TreeGen.scala
* When constructing the `fieldDefs`, it is important to adapt their
range position to avoid overlappings with the positions of default
arguments. It is worth noting that updating the field's end position
to `vd.rhs.pos.start` would be incorrect, because `askTypeAt(pos)`
could return the incorrect tree when the position is equal to
`vd.rhs.pos.start` (because two nodes including that point position
would exist in the tree, and `CompilerControl.locateTree(pos)` would
return the first tree that includes the passed `pos`). This is why
`1` is subtracted to `vd.rhs.pos.start`. Alternatively, we could have
used `vd.tpt.pos.end` with similar results. However the logic would
have become slightly more complex as we would need to handle the case
where `vd.tpt` doesn't have a range position (for instance, this can
happen if `-Yinfer-argument-types` is enabled). Therefore, subtracting
`1` from `vd.rhs.pos.start` seemed the cleanest solution at the
moment. - see changes in TreeGen.scala.
* If the synthetic constructor contains trees with an opaque range
position (see point above), it must have a transparent position.
This can only happen if the constructor's parameters' positions are
considered, which is why we are now passing `vparamss1` to
`wrappingPos` - see changes in TreeGen.scala.
* The derived primary constructor should have a transparent position
as it may contain trees with an opaque range position. Hence, the
`primaryCtor` position is considered for computing the position of the
derived constructor - see change in Typers.scala.
Finally, below follows the printing of the tree for test t4287, which
you should compare with the one attached with the previous commit
message:
```
[[syntax trees at end of typer]] // Foo.scala
[0:63]package [0:0]<empty> {
[0:37]class Baz extends [9:37][39]scala.AnyRef {
[10:20]<paramaccessor> private[this] val f: [14]Int = _;
[14]<stable> <accessor> <paramaccessor> def f: [14]Int = [14][14]Baz.this.f;
<10:31>def <init>(<10:31>f: [17]<type: [17]scala.Int> = [23:31]B.a): [9]Baz = <10:31>{
<10:31><10:31><10:31>Baz.super.<init>();
<10:31>()
}
};
[6]<synthetic> object Baz extends [6][6]AnyRef {
[6]def <init>(): [9]Baz.type = [6]{
[6][6][6]Baz.super.<init>();
[9]()
};
[14]<synthetic> def <init>$default$1: [14]Int = [30]B.a
};
[39:63]object B extends [48:63][63]scala.AnyRef {
[63]def <init>(): [48]B.type = [63]{
[63][63][63]B.super.<init>();
[48]()
};
[52:61]private[this] val a: [56]Int = [60:61]2;
[56]<stable> <accessor> def a: [56]Int = [56][56]B.this.a
}
}
```
You should notice that the default arg of `Baz` constructor now has a
range position. And that explains why the associated test now returns
the right tree when asking hyperlinking at the location of the default
argument.
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