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Fix #1568 - avoid transforming error trees #1930

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Merged
merged 1 commit into from
Feb 2, 2017
Merged

Fix #1568 - avoid transforming error trees #1930

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179 changes: 92 additions & 87 deletions compiler/src/dotty/tools/dotc/ast/Trees.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1069,95 +1069,100 @@ object Trees {
Template(tree: Tree)(constr, parents, self, body)
}

/** Hook to indicate that a transform of some subtree should be skipped */
protected def skipTransform(tree: Tree)(implicit ctx: Context): Boolean = false

abstract class TreeMap(val cpy: TreeCopier = inst.cpy) {

def transform(tree: Tree)(implicit ctx: Context): Tree = tree match {
case Ident(name) =>
tree
case Select(qualifier, name) =>
cpy.Select(tree)(transform(qualifier), name)
case This(qual) =>
tree
case Super(qual, mix) =>
cpy.Super(tree)(transform(qual), mix)
case Apply(fun, args) =>
cpy.Apply(tree)(transform(fun), transform(args))
case TypeApply(fun, args) =>
cpy.TypeApply(tree)(transform(fun), transform(args))
case Literal(const) =>
tree
case New(tpt) =>
cpy.New(tree)(transform(tpt))
case Typed(expr, tpt) =>
cpy.Typed(tree)(transform(expr), transform(tpt))
case NamedArg(name, arg) =>
cpy.NamedArg(tree)(name, transform(arg))
case Assign(lhs, rhs) =>
cpy.Assign(tree)(transform(lhs), transform(rhs))
case Block(stats, expr) =>
cpy.Block(tree)(transformStats(stats), transform(expr))
case If(cond, thenp, elsep) =>
cpy.If(tree)(transform(cond), transform(thenp), transform(elsep))
case Closure(env, meth, tpt) =>
cpy.Closure(tree)(transform(env), transform(meth), transform(tpt))
case Match(selector, cases) =>
cpy.Match(tree)(transform(selector), transformSub(cases))
case CaseDef(pat, guard, body) =>
cpy.CaseDef(tree)(transform(pat), transform(guard), transform(body))
case Return(expr, from) =>
cpy.Return(tree)(transform(expr), transformSub(from))
case Try(block, cases, finalizer) =>
cpy.Try(tree)(transform(block), transformSub(cases), transform(finalizer))
case SeqLiteral(elems, elemtpt) =>
cpy.SeqLiteral(tree)(transform(elems), transform(elemtpt))
case Inlined(call, bindings, expansion) =>
cpy.Inlined(tree)(call, transformSub(bindings), transform(expansion))
case TypeTree() =>
tree
case SingletonTypeTree(ref) =>
cpy.SingletonTypeTree(tree)(transform(ref))
case AndTypeTree(left, right) =>
cpy.AndTypeTree(tree)(transform(left), transform(right))
case OrTypeTree(left, right) =>
cpy.OrTypeTree(tree)(transform(left), transform(right))
case RefinedTypeTree(tpt, refinements) =>
cpy.RefinedTypeTree(tree)(transform(tpt), transformSub(refinements))
case AppliedTypeTree(tpt, args) =>
cpy.AppliedTypeTree(tree)(transform(tpt), transform(args))
case PolyTypeTree(tparams, body) =>
cpy.PolyTypeTree(tree)(transformSub(tparams), transform(body))
case ByNameTypeTree(result) =>
cpy.ByNameTypeTree(tree)(transform(result))
case TypeBoundsTree(lo, hi) =>
cpy.TypeBoundsTree(tree)(transform(lo), transform(hi))
case Bind(name, body) =>
cpy.Bind(tree)(name, transform(body))
case Alternative(trees) =>
cpy.Alternative(tree)(transform(trees))
case UnApply(fun, implicits, patterns) =>
cpy.UnApply(tree)(transform(fun), transform(implicits), transform(patterns))
case EmptyValDef =>
tree
case tree @ ValDef(name, tpt, _) =>
val tpt1 = transform(tpt)
val rhs1 = transform(tree.rhs)
cpy.ValDef(tree)(name, tpt1, rhs1)
case tree @ DefDef(name, tparams, vparamss, tpt, _) =>
cpy.DefDef(tree)(name, transformSub(tparams), vparamss mapConserve (transformSub(_)), transform(tpt), transform(tree.rhs))
case tree @ TypeDef(name, rhs) =>
cpy.TypeDef(tree)(name, transform(rhs))
case tree @ Template(constr, parents, self, _) =>
cpy.Template(tree)(transformSub(constr), transform(parents), transformSub(self), transformStats(tree.body))
case Import(expr, selectors) =>
cpy.Import(tree)(transform(expr), selectors)
case PackageDef(pid, stats) =>
cpy.PackageDef(tree)(transformSub(pid), transformStats(stats))
case Annotated(arg, annot) =>
cpy.Annotated(tree)(transform(arg), transform(annot))
case Thicket(trees) =>
val trees1 = transform(trees)
if (trees1 eq trees) tree else Thicket(trees1)
}
def transform(tree: Tree)(implicit ctx: Context): Tree =
if (skipTransform(tree)) tree
else tree match {
case Ident(name) =>
tree
case Select(qualifier, name) =>
cpy.Select(tree)(transform(qualifier), name)
case This(qual) =>
tree
case Super(qual, mix) =>
cpy.Super(tree)(transform(qual), mix)
case Apply(fun, args) =>
cpy.Apply(tree)(transform(fun), transform(args))
case TypeApply(fun, args) =>
cpy.TypeApply(tree)(transform(fun), transform(args))
case Literal(const) =>
tree
case New(tpt) =>
cpy.New(tree)(transform(tpt))
case Typed(expr, tpt) =>
cpy.Typed(tree)(transform(expr), transform(tpt))
case NamedArg(name, arg) =>
cpy.NamedArg(tree)(name, transform(arg))
case Assign(lhs, rhs) =>
cpy.Assign(tree)(transform(lhs), transform(rhs))
case Block(stats, expr) =>
cpy.Block(tree)(transformStats(stats), transform(expr))
case If(cond, thenp, elsep) =>
cpy.If(tree)(transform(cond), transform(thenp), transform(elsep))
case Closure(env, meth, tpt) =>
cpy.Closure(tree)(transform(env), transform(meth), transform(tpt))
case Match(selector, cases) =>
cpy.Match(tree)(transform(selector), transformSub(cases))
case CaseDef(pat, guard, body) =>
cpy.CaseDef(tree)(transform(pat), transform(guard), transform(body))
case Return(expr, from) =>
cpy.Return(tree)(transform(expr), transformSub(from))
case Try(block, cases, finalizer) =>
cpy.Try(tree)(transform(block), transformSub(cases), transform(finalizer))
case SeqLiteral(elems, elemtpt) =>
cpy.SeqLiteral(tree)(transform(elems), transform(elemtpt))
case Inlined(call, bindings, expansion) =>
cpy.Inlined(tree)(call, transformSub(bindings), transform(expansion))
case TypeTree() =>
tree
case SingletonTypeTree(ref) =>
cpy.SingletonTypeTree(tree)(transform(ref))
case AndTypeTree(left, right) =>
cpy.AndTypeTree(tree)(transform(left), transform(right))
case OrTypeTree(left, right) =>
cpy.OrTypeTree(tree)(transform(left), transform(right))
case RefinedTypeTree(tpt, refinements) =>
cpy.RefinedTypeTree(tree)(transform(tpt), transformSub(refinements))
case AppliedTypeTree(tpt, args) =>
cpy.AppliedTypeTree(tree)(transform(tpt), transform(args))
case PolyTypeTree(tparams, body) =>
cpy.PolyTypeTree(tree)(transformSub(tparams), transform(body))
case ByNameTypeTree(result) =>
cpy.ByNameTypeTree(tree)(transform(result))
case TypeBoundsTree(lo, hi) =>
cpy.TypeBoundsTree(tree)(transform(lo), transform(hi))
case Bind(name, body) =>
cpy.Bind(tree)(name, transform(body))
case Alternative(trees) =>
cpy.Alternative(tree)(transform(trees))
case UnApply(fun, implicits, patterns) =>
cpy.UnApply(tree)(transform(fun), transform(implicits), transform(patterns))
case EmptyValDef =>
tree
case tree @ ValDef(name, tpt, _) =>
val tpt1 = transform(tpt)
val rhs1 = transform(tree.rhs)
cpy.ValDef(tree)(name, tpt1, rhs1)
case tree @ DefDef(name, tparams, vparamss, tpt, _) =>
cpy.DefDef(tree)(name, transformSub(tparams), vparamss mapConserve (transformSub(_)), transform(tpt), transform(tree.rhs))
case tree @ TypeDef(name, rhs) =>
cpy.TypeDef(tree)(name, transform(rhs))
case tree @ Template(constr, parents, self, _) =>
cpy.Template(tree)(transformSub(constr), transform(parents), transformSub(self), transformStats(tree.body))
case Import(expr, selectors) =>
cpy.Import(tree)(transform(expr), selectors)
case PackageDef(pid, stats) =>
cpy.PackageDef(tree)(transformSub(pid), transformStats(stats))
case Annotated(arg, annot) =>
cpy.Annotated(tree)(transform(arg), transform(annot))
case Thicket(trees) =>
val trees1 = transform(trees)
if (trees1 eq trees) tree else Thicket(trees1)
}

def transformStats(trees: List[Tree])(implicit ctx: Context): List[Tree] =
transform(trees)
Expand Down
2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/ast/tpd.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -573,6 +573,8 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
Try(tree: Tree)(expr, cases, finalizer)
}

override def skipTransform(tree: Tree)(implicit ctx: Context) = tree.tpe.isError
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It might be cleaner to just override the transform as follows:

override def transform(tree: Tree)(implicit ctx: Context): Tree = 
  if (tree.tpe.isError) tree else super.transform(tree)

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I was debating what was simpler, and more efficient. I also first thought of overriding transform, but: (1) this requires a new TreeMap class in tpd (2) this adds a stackframe to each node traversal, which can add up. So I think the current approach is more lightweight in the end.


implicit class TreeOps[ThisTree <: tpd.Tree](val tree: ThisTree) extends AnyVal {

def isValue(implicit ctx: Context): Boolean =
Expand Down
3 changes: 3 additions & 0 deletions tests/neg/i1568.scala
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@@ -0,0 +1,3 @@
object Test {
inline def foo(n: Int) = foo(n) // error: cyclic reference
}