diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/transform/LambdaLift.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/transform/LambdaLift.scala | 41 |
1 files changed, 33 insertions, 8 deletions
diff --git a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala index 448079abed..845843e9d6 100644 --- a/src/compiler/scala/tools/nsc/transform/LambdaLift.scala +++ b/src/compiler/scala/tools/nsc/transform/LambdaLift.scala @@ -451,20 +451,45 @@ abstract class LambdaLift extends InfoTransform { } case arg => arg } - /** Wrap expr argument in new *Ref(..) constructor, but make - * sure that Try expressions stay at toplevel. + + /** Wrap expr argument in new *Ref(..) constructor. But try/catch + * is a problem because a throw will clear the stack and post catch + * we would expect the partially-constructed object to be on the stack + * for the call to init. So we recursively + * search for "leaf" result expressions where we know its safe + * to put the new *Ref(..) constructor or, if all else fails, transform + * an expr to { val temp=expr; new *Ref(temp) }. + * The reason we narrowly look for try/catch in captured var definitions + * is because other try/catch expression have already been lifted + * see SI-6863 */ - def refConstr(expr: Tree): Tree = expr match { + def refConstr(expr: Tree): Tree = typer.typedPos(expr.pos) {expr match { + // very simple expressions can be wrapped in a new *Ref(expr) because they can't have + // a try/catch in final expression position. + case Ident(_) | Apply(_, _) | Literal(_) | New(_) | Select(_, _) | Throw(_) | Assign(_, _) | ValDef(_, _, _, _) | Return(_) | EmptyTree => + New(sym.tpe, expr) case Try(block, catches, finalizer) => Try(refConstr(block), catches map refConstrCase, finalizer) + case Block(stats, expr) => + Block(stats, refConstr(expr)) + case If(cond, trueBranch, falseBranch) => + If(cond, refConstr(trueBranch), refConstr(falseBranch)) + case Match(selector, cases) => + Match(selector, cases map refConstrCase) + // if we can't figure out what else to do, turn expr into {val temp1 = expr; new *Ref(temp1)} to avoid + // any possibility of try/catch in the *Ref constructor. This should be a safe tranformation as a default + // though it potentially wastes a variable slot. In particular this case handles LabelDefs. case _ => - New(sym.tpe, expr) - } + debuglog("assigning expr to temp: " + (expr.pos)) + val tempSym = currentOwner.newValue(unit.freshTermName("temp"), expr.pos) setInfo expr.tpe + val tempDef = ValDef(tempSym, expr) setPos expr.pos + val tempRef = Ident(tempSym) setPos expr.pos + Block(tempDef, New(sym.tpe, tempRef)) + }} def refConstrCase(cdef: CaseDef): CaseDef = CaseDef(cdef.pat, cdef.guard, refConstr(cdef.body)) - treeCopy.ValDef(tree, mods, name, tpt1, typer.typedPos(rhs.pos) { - refConstr(constructorArg) - }) + + treeCopy.ValDef(tree, mods, name, tpt1, refConstr(constructorArg)) } else tree case Return(Block(stats, value)) => Block(stats, treeCopy.Return(tree, value)) setType tree.tpe setPos tree.pos |