From 96b012aa48e3d91f8ec6d5221df2f455f278c9e0 Mon Sep 17 00:00:00 2001 From: Som Snytt Date: Fri, 26 Jun 2015 21:32:29 -0700 Subject: Improved message for missing argument list Clarifies the language and rules for eta-expansion. A missing argument in a list, as opposed to a missing argument list, results in a different message. The comical expansion in parens does not attempt to show what was already applied, but succeeds in showing at a glance the shape of the method in question. ``` scala> def m(i: Int, j: Int)(x: Int) = ??? m: (i: Int, j: Int)(x: Int)Nothing scala> m :12: error: missing argument list for method m Unapplied methods are only converted to functions when a function type is expected. You can make this conversion explicit by writing `m _` or `m(_,_)(_)` instead of `m`. m ^ ``` The original submission was due to sschaef and the wording due to adriaanm, with a minor tweak. --- .../tools/nsc/typechecker/ContextErrors.scala | 37 +++++++++++----------- test/files/neg/macro-invalidshape.check | 5 +-- test/files/neg/missing-arg-list.check | 21 ++++++++++++ test/files/neg/missing-arg-list.scala | 13 ++++++++ 4 files changed, 55 insertions(+), 21 deletions(-) create mode 100644 test/files/neg/missing-arg-list.check create mode 100644 test/files/neg/missing-arg-list.scala diff --git a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala index c80aaea160..b0bd9977a8 100644 --- a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala +++ b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala @@ -550,23 +550,18 @@ trait ContextErrors { def ModuleUsingCompanionClassDefaultArgsErrror(tree: Tree) = NormalTypeError(tree, "module extending its companion class cannot use default constructor arguments") - def NotEnoughArgsError(tree: Tree, fun0: Tree, missing0: List[Symbol]) = { - def notEnoughArgumentsMsg(fun: Tree, missing: List[Symbol]) = { - val suffix = { - if (missing.isEmpty) "" - else { - val keep = missing take 3 map (_.name) - ".\nUnspecified value parameter%s %s".format( - if (missing.tail.isEmpty) "" else "s", - if ((missing drop 3).nonEmpty) (keep :+ "...").mkString(", ") - else keep.mkString("", ", ", ".") - ) - } + def NotEnoughArgsError(tree: Tree, fun: Tree, missing: List[Symbol]) = { + val notEnoughArgumentsMsg = { + val suffix = if (missing.isEmpty) "" else { + val keep = missing take 3 map (_.name) + val ess = if (missing.tail.isEmpty) "" else "s" + f".%nUnspecified value parameter$ess ${ + keep.mkString("", ", ", if ((missing drop 3).nonEmpty) "..." else ".") + }" } - - "not enough arguments for " + treeSymTypeMsg(fun) + suffix + s"not enough arguments for ${ treeSymTypeMsg(fun) }$suffix" } - NormalTypeError(tree, notEnoughArgumentsMsg(fun0, missing0)) + NormalTypeError(tree, notEnoughArgumentsMsg) } //doTypedApply - patternMode @@ -632,12 +627,16 @@ trait ContextErrors { //adapt def MissingArgsForMethodTpeError(tree: Tree, meth: Symbol) = { + val f = meth.name + val paf = s"$f(${ meth.asMethod.paramLists map (_ map (_ => "_") mkString ",") mkString ")(" })" + val advice = s""" + |Unapplied methods are only converted to functions when a function type is expected. + |You can make this conversion explicit by writing `$f _` or `$paf` instead of `$f`.""".stripMargin val message = if (meth.isMacro) MacroTooFewArgumentListsMessage - else "missing arguments for " + meth.fullLocationString + ( - if (meth.isConstructor) "" - else ";\nfollow this method with `_' if you want to treat it as a partially applied function" - ) + else s"""missing argument list for ${meth.fullLocationString}${ + if (!meth.isConstructor) advice else "" + }""" issueNormalTypeError(tree, message) setError(tree) } diff --git a/test/files/neg/macro-invalidshape.check b/test/files/neg/macro-invalidshape.check index aa694df6d6..5093b87598 100644 --- a/test/files/neg/macro-invalidshape.check +++ b/test/files/neg/macro-invalidshape.check @@ -8,8 +8,9 @@ macro [].[[]] or macro [].[[]] def foo2(x: Any) = macro Impls.foo(null)(null) ^ -Macros_Test_2.scala:4: error: missing arguments for method foo in object Impls; -follow this method with `_' if you want to treat it as a partially applied function +Macros_Test_2.scala:4: error: missing argument list for method foo in object Impls +Unapplied methods are only converted to functions when a function type is expected. +You can make this conversion explicit by writing `foo _` or `foo(_)(_)` instead of `foo`. def foo3(x: Any) = macro {2; Impls.foo} ^ Macros_Test_2.scala:7: error: macro implementation reference has wrong shape. required: diff --git a/test/files/neg/missing-arg-list.check b/test/files/neg/missing-arg-list.check new file mode 100644 index 0000000000..5a011c36f2 --- /dev/null +++ b/test/files/neg/missing-arg-list.check @@ -0,0 +1,21 @@ +missing-arg-list.scala:9: error: missing argument list for method id in trait T +Unapplied methods are only converted to functions when a function type is expected. +You can make this conversion explicit by writing `id _` or `id(_)` instead of `id`. + val w = id + ^ +missing-arg-list.scala:10: error: missing argument list for method f in trait T +Unapplied methods are only converted to functions when a function type is expected. +You can make this conversion explicit by writing `f _` or `f(_)(_)` instead of `f`. + val x = f + ^ +missing-arg-list.scala:11: error: missing argument list for method g in trait T +Unapplied methods are only converted to functions when a function type is expected. +You can make this conversion explicit by writing `g _` or `g(_,_,_)` instead of `g`. + val y = g + ^ +missing-arg-list.scala:12: error: missing argument list for method h in trait T +Unapplied methods are only converted to functions when a function type is expected. +You can make this conversion explicit by writing `h _` or `h(_,_,_)(_)` instead of `h`. + val z = h + ^ +four errors found diff --git a/test/files/neg/missing-arg-list.scala b/test/files/neg/missing-arg-list.scala new file mode 100644 index 0000000000..c422dd32fe --- /dev/null +++ b/test/files/neg/missing-arg-list.scala @@ -0,0 +1,13 @@ + +trait T { + + def id(i: Int) = i + def f(i: Int)(j: Int) = i+j + def g(i: Int, j: Int, k: Int) = i+j+k + def h(i: Int, j: Int, k: Int)(implicit s: String) = s*(i+j+k) + + val w = id + val x = f + val y = g + val z = h +} -- cgit v1.2.3