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author | Paul Phillips <paulp@improving.org> | 2012-07-21 19:49:55 -0700 |
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committer | Paul Phillips <paulp@improving.org> | 2012-07-27 05:42:17 -0700 |
commit | bc719cb8e4957a80e423350d8e993f1fa6a2a997 (patch) | |
tree | 2939e8688721c66fd1493bdadf9260d75faa4514 /src/compiler | |
parent | ad08f24448729009fc8d5ff0acf307a43b4cfe0a (diff) | |
download | scala-bc719cb8e4957a80e423350d8e993f1fa6a2a997.tar.gz scala-bc719cb8e4957a80e423350d8e993f1fa6a2a997.tar.bz2 scala-bc719cb8e4957a80e423350d8e993f1fa6a2a997.zip |
Improve unchecked warnings a lot.
Don't warn on "uncheckable" type patterns if they can be
statically guaranteed, regardless of their runtime checkability.
This covers patterns like Seq[Any] and lots more.
Review by @adriaanm.
Diffstat (limited to 'src/compiler')
3 files changed, 82 insertions, 57 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala index bcbcb96400..e096b75d6d 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala @@ -1324,66 +1324,89 @@ trait Infer { } // if top-level abstract types can be checked using a classtag extractor, don't warn about them - def checkCheckable(tree: Tree, tp: Type, inPattern: Boolean, canRemedy: Boolean = false) = { - val kind = if (inPattern) "pattern " else "" + def checkCheckable(tree: Tree, typeToTest: Type, typeEnsured: Type, inPattern: Boolean, canRemedy: Boolean = false) = { + log(s"checkCheckable($tree, $typeToTest, $typeEnsured, inPattern = $inPattern, canRemedy = $canRemedy") - def patternWarning(tp0: Type, prefix: String) = { - context.unit.uncheckedWarning(tree.pos, prefix+tp0+" in type "+kind+tp+" is unchecked since it is eliminated by erasure") + sealed abstract class TypeConformance(check: (Type, Type) => Boolean) { + def apply(t1: Type, t2: Type): Boolean = check(t1, t2) && { + log(s"Skipping unchecked for statically verifiable condition $t1 ${this} $t2") + true + } } - def check(tp: Type, bound: List[Symbol]) { - def isLocalBinding(sym: Symbol) = - sym.isAbstractType && - ((bound contains sym) || - sym.name == tpnme.WILDCARD || { + // I tried to use varianceInType to track the variance implications + // but I could not make it work. + case object =:= extends TypeConformance(_ =:= _) + case object <:< extends TypeConformance(_ <:< _) + case object >:> extends TypeConformance((t1, t2) => t2 <:< t1) + case object =!= extends TypeConformance((t1, t2) => false) + + var bound: List[Symbol] = Nil + var warningMessages: List[String] = Nil + + def isLocalBinding(sym: Symbol) = ( + sym.isAbstractType && ( + (bound contains sym) + || (sym.name == tpnme.WILDCARD) + || { val e = context.scope.lookupEntry(sym.name) (e ne null) && e.sym == sym && !e.sym.isTypeParameterOrSkolem && e.owner == context.scope - }) - tp match { - case SingleType(pre, _) => - check(pre, bound) - case TypeRef(pre, sym, args) => - if (sym.isAbstractType) { - // we only use the extractor for top-level type tests, type arguments (see below) remain unchecked - if (!isLocalBinding(sym) && !canRemedy) patternWarning(tp, "abstract type ") - } else if (sym.isAliasType) { - check(tp.normalize, bound) - } else if (sym == NothingClass || sym == NullClass || sym == AnyValClass) { - TypePatternOrIsInstanceTestError(tree, tp) - } else { - for (arg <- args) { - if (sym == ArrayClass) check(arg, bound) - // avoid spurious warnings with higher-kinded types - else if (arg.typeArgs exists (_.typeSymbol.isTypeParameterOrSkolem)) () - // no way to suppress unchecked warnings on try/catch - else if (sym == NonLocalReturnControlClass) () - else arg match { - case TypeRef(_, sym, _) if isLocalBinding(sym) => - ; - case _ => - // Want to warn about type arguments, not type parameters. Otherwise we'll - // see warnings about "invisible" types, like: val List(x0) = x1 leading to "non - // variable type-argument A in type pattern List[A]..." - if (!arg.typeSymbol.isTypeParameterOrSkolem) - patternWarning(arg, "non variable type-argument ") - } - } - } - check(pre, bound) - case RefinedType(parents, decls) => - if (decls.isEmpty) for (p <- parents) check(p, bound) - else patternWarning(tp, "refinement ") - case ExistentialType(quantified, tp1) => - check(tp1, bound ::: quantified) - case ThisType(_) => - () - case NoPrefix => - () - case _ => - patternWarning(tp, "type ") - () + } + ) + ) + def check(tp0: Type, pt: Type, conformance: TypeConformance): Boolean = { + val tp = tp0.normalize + // Set the warning message to be issued when the top-level call fails. + def warn(what: String): Boolean = { + warningMessages ::= what + false + } + def checkArg(param: Symbol, arg: Type) = { + def conforms = ( + if (param.isCovariant) <:< + else if (param.isContravariant) >:> + else =:= + ) + val TypeRef(_, sym, args) = arg + + ( isLocalBinding(sym) + || arg.typeSymbol.isTypeParameterOrSkolem + || (sym.name == tpnme.WILDCARD) // avoid spurious warnings on HK types + || check(arg, param.tpe, conforms) + || warn("non-variable type argument " + arg) + ) } + + // Checking if pt (the expected type of the pattern, and the type + // we are guaranteed) conforms to tp (the type expressed in the pattern's + // type test.) If it does, then even if the type being checked for appears + // to be uncheckable, it is not a warning situation, because it is indeed + // checked: not at runtime, but statically. + conformance.apply(pt, tp) || (tp match { + case SingleType(pre, _) => check(pre, pt, =:=) + case ExistentialType(quantified, tp1) => bound :::= quantified ; check(tp1, pt, <:<) + case ThisType(_) | NoPrefix => true + case RefinedType(parents, decls) if decls.isEmpty => parents forall (p => check(p, pt, <:<)) + case RefinedType(_, _) => warn("refinement " + tp) + case TypeRef(_, ArrayClass, arg :: Nil) => check(arg, NoType, =!=) + case TypeRef(_, NonLocalReturnControlClass, _) => true // no way to suppress unchecked warnings on try/catch + // we only use the extractor for top-level type tests, type arguments remain unchecked + case TypeRef(_, sym, _) if sym.isAbstractType => isLocalBinding(sym) || canRemedy || warn("abstract type " + tp) + case TypeRef(_, _, Nil) => false // leaf node + case TypeRef(pre, sym, args) => forall2(sym.typeParams, args)(checkArg) && check(pre, pt.prefix, =:=) + case _ => warn("type " + tp) + }) + } + typeToTest match { + // Prohibit top-level type tests for these, but they are + // acceptable nested (e.g. case Foldable[Nothing] => ... ) + case TypeRef(_, NothingClass | NullClass | AnyValClass, _) => + TypePatternOrIsInstanceTestError(tree, typeToTest) + case _ => + def where = ( if (inPattern) "pattern " else "" ) + typeToTest + if (check(typeToTest, typeEnsured, =:=)) () + else warningMessages foreach (m => + context.unit.uncheckedWarning(tree.pos, s"$m in type $where is unchecked since it is eliminated by erasure")) } - check(tp, List()) } /** Type intersection of simple type tp1 with general type tp2. @@ -1420,7 +1443,7 @@ trait Infer { return ErrorType } - checkCheckable(tree0, pattp, inPattern = true, canRemedy) + checkCheckable(tree0, pattp, pt, inPattern = true, canRemedy) if (pattp <:< pt) () else { debuglog("free type params (1) = " + tpparams) diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala index 8b7c70c048..cf5c7265ad 100644 --- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala +++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala @@ -412,8 +412,9 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL **/ // must treat Typed and Bind together -- we need to know the patBinder of the Bind pattern to get at the actual type case MaybeBoundTyped(subPatBinder, pt) => + val next = glb(List(patBinder.info.widen, pt)).normalize // a typed pattern never has any subtrees - noFurtherSubPats(TypeTestTreeMaker(subPatBinder, patBinder, pt, glb(List(patBinder.info.widen, pt)).normalize)(pos)) + noFurtherSubPats(TypeTestTreeMaker(subPatBinder, patBinder, pt, next)(pos)) /** A pattern binder x@p consists of a pattern variable x and a pattern p. The type of the variable x is the static type T of the pattern p. diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala index 51753baa4f..269ab9611a 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala @@ -3672,7 +3672,8 @@ trait Typers extends Modes with Adaptations with Tags { typedClassOf(tree, args.head, true) else { if (!isPastTyper && fun.symbol == Any_isInstanceOf && !targs.isEmpty) - checkCheckable(tree, targs.head, inPattern = false) + checkCheckable(tree, targs.head, AnyClass.tpe, inPattern = false) + val resultpe = restpe.instantiateTypeParams(tparams, targs) //@M substitution in instantiateParams needs to be careful! //@M example: class Foo[a] { def foo[m[x]]: m[a] = error("") } (new Foo[Int]).foo[List] : List[Int] |