Add partial evaluation of isInstanceOf mini-phase
#1275
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| * match | ||
| */ | ||
| def handleStaticallyKnown(tree: Select, scrutinee: Type, selector: Type, inMatch: Boolean, pos: Position): Tree = | ||
| if (!(scrutinee <:< selector) && inMatch) { |
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it may be better to compute scrutinee <:< selector only once.
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/rebuild |
| else if (falseIfUnrelated && !(selector <:< scrutinee)) | ||
| // selector and scrutinee are unrelated | ||
| handleFalseUnrelated(s, scrutinee, selector, inMatch) | ||
| else if (happens) tree |
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there's no difference between happens and !happens
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Agreed, it was kept to showcase all cases - but I'll change it to and note this in a comment.
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| * `scrutinee.isInstanceOf[Selector]` if `scrutinee eq null` | ||
| */ | ||
| def rewrite(tree: Select, to: Boolean): Tree = | ||
| if (!to || !tree.qualifier.tpe.widen.derivesFrom(defn.AnyRefAlias)) |
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Counterexample:
def foo = {println(1); 1}.isInstanceOf[Int]need to check if tpd.isPure(tree.qual). If not, rewrite to Block(List(tree.qual), Literal(Constant(to))).
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/rebuild |
| if (!to || !tree.qualifier.tpe.widen.derivesFrom(defn.AnyRefAlias)) | ||
| Literal(Constant(to)) | ||
| else | ||
| Apply(tree.qualifier.select(defn.Object_ne), List(Literal(Constant(null)))) |
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if tree.qualifier is not pure, it will be computed twice
The tests `i1059.scala` and `t3480.scala` are failing due to a bug in pattern matcher that evaluates the `x` in `List(x: _*)` incorrectly. Concerned issue: scala#1276
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LGTM |
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In #1255 it was suggested to add a mini-phase that would simply partially evaluate calls to
isInstanceOfand issue warnings/errors where appropriate.This PR adds the ability to discern if the transformed tree came from a
matchor from anifas well as the proper error messages and warnings.The following example will yield an error:
While the following will yield a warning: