From 8ed7099f7db6a1060a490a594c958ca9a8b41487 Mon Sep 17 00:00:00 2001 From: Jason Zaugg Date: Mon, 7 Oct 2013 15:06:22 +0200 Subject: SI-7899 Don't infer by-name types during, e.g. eta-expansion Given: def id[A](a: A): A = a def foo(f: (=> Int) => Int) = () foo(id) We eta-expanded `id` and inferred `A` to be `=> Int` to satisfy the expected type set forth by the formal parameter `f`. We really shouldn't go about inferring types that we can't *write*. Our attempt to do so led promptly into a `ClassCastException` in the enclosed test. This commit: - drops by-name-ness during `inferExprInstance` - tests that this results in a type error for the reported bug (neg/t7899) - tests that a method with a by-name parameter can still be eta expanded to match function with a corresponding by-name parameter (run/t7899) - discovers the same latent CCE in pos/t7584 - now that would be a type error - so we compensate by using placeholder functions rather than eta-expansion. - and move that that test to `run` for good measure. --- src/compiler/scala/tools/nsc/typechecker/Infer.scala | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'src') diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala index 03f680525c..ccf4a5e46f 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala @@ -913,12 +913,13 @@ trait Infer extends Checkable { val targs = exprTypeArgs(tvars, tparams, treeTp, pt, useWeaklyCompatible) def infer_s = map3(tparams, tvars, targs)((tparam, tvar, targ) => s"$tparam=$tvar/$targ") mkString "," printTyping(tree, s"infer expr instance from pt=$pt, $infer_s") + def targsStrict = if (targs eq null) null else targs mapConserve dropByName if (keepNothings || (targs eq null)) { //@M: adjustTypeArgs fails if targs==null, neg/t0226 - substExpr(tree, tparams, targs, pt) + substExpr(tree, tparams, targsStrict, pt) List() } else { - val AdjustedTypeArgs.Undets(okParams, okArgs, leftUndet) = adjustTypeArgs(tparams, tvars, targs) + val AdjustedTypeArgs.Undets(okParams, okArgs, leftUndet) = adjustTypeArgs(tparams, tvars, targsStrict) def solved_s = map2(okParams, okArgs)((p, a) => s"$p=$a") mkString "," def undet_s = leftUndet match { case Nil => "" -- cgit v1.2.3