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author | Jason Zaugg <jzaugg@gmail.com> | 2013-02-10 23:13:28 +0100 |
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committer | Jason Zaugg <jzaugg@gmail.com> | 2013-02-10 23:21:49 +0100 |
commit | 673cc83f198322b3346be2bddea7ff05bd6f0f5b (patch) | |
tree | 13bdc50189bc44d0548a01e9ba07a001dd74b45d | |
parent | 23b69c1e05474dc6b504d63c074629132264deaf (diff) | |
download | scala-673cc83f198322b3346be2bddea7ff05bd6f0f5b.tar.gz scala-673cc83f198322b3346be2bddea7ff05bd6f0f5b.tar.bz2 scala-673cc83f198322b3346be2bddea7ff05bd6f0f5b.zip |
SI-6514 Avoid spurious dead code warnings
`deadCode.expr` stores the method symbol most recently encountered
in `handleMonomorphicCall`, and uses this to avoid warnings
for arguments to label jumps and `Object#synchronized` (which
sneakily acts by-name without advertising the fact in its type.)
But this scheme was insufficient if the argument itself contains
another method call, such as `matchEnd(throw e(""))`.
This commit changes the single slot to a stack, and also
grants exemption to `LabelDef` trees. They were incorrectly
flagged in the enclosed test case after I made the the first change.
-rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala | 17 | ||||
-rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/Typers.scala | 6 | ||||
-rw-r--r-- | test/files/pos/t6514.scala | 11 |
3 files changed, 26 insertions, 8 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala index 4233bde770..8c21479f73 100644 --- a/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala +++ b/src/compiler/scala/tools/nsc/typechecker/TypeDiagnostics.scala @@ -427,17 +427,24 @@ trait TypeDiagnostics { contextWarning(pos, "imported `%s' is permanently hidden by definition of %s".format(hidden, defn.fullLocationString)) object checkDead { - private var expr: Symbol = NoSymbol + private val exprStack: mutable.Stack[Symbol] = mutable.Stack(NoSymbol) + // The method being applied to `tree` when `apply` is called. + private def expr = exprStack.top private def exprOK = (expr != Object_synchronized) && !(expr.isLabel && treeInfo.isSynthCaseSymbol(expr)) // it's okay to jump to matchEnd (or another case) with an argument of type nothing - private def treeOK(tree: Tree) = tree.tpe != null && tree.tpe.typeSymbol == NothingClass + private def treeOK(tree: Tree) = { + val isLabelDef = tree match { case _: LabelDef => true; case _ => false} + tree.tpe != null && tree.tpe.typeSymbol == NothingClass && !isLabelDef + } - def updateExpr(fn: Tree) = { - if (fn.symbol != null && fn.symbol.isMethod && !fn.symbol.isConstructor) - checkDead.expr = fn.symbol + @inline def updateExpr[A](fn: Tree)(f: => A) = { + if (fn.symbol != null && fn.symbol.isMethod && !fn.symbol.isConstructor) { + exprStack push fn.symbol + try f finally exprStack.pop() + } else f } def apply(tree: Tree): Tree = { // Error suppression will squash some of these warnings unless we circumvent it. diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala index dc5491a509..ce5d3cba7a 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala @@ -3305,8 +3305,6 @@ trait Typers extends Modes with Adaptations with Tags { // but behaves as if it were (=> T) => T) we need to know what is the actual // target of a call. Since this information is no longer available from // typedArg, it is recorded here. - checkDead.updateExpr(fun) - val args1 = // no expected type when jumping to a match label -- anything goes (this is ok since we're typing the translation of well-typed code) // ... except during erasure: we must take the expected type into account as it drives the insertion of casts! @@ -3361,7 +3359,9 @@ trait Typers extends Modes with Adaptations with Tags { else constfold(treeCopy.Apply(tree, fun, args1) setType ifPatternSkipFormals(restpe)) } - handleMonomorphicCall + checkDead.updateExpr(fun) { + handleMonomorphicCall + } } else if (needsInstantiation(tparams, formals, args)) { //println("needs inst "+fun+" "+tparams+"/"+(tparams map (_.info))) inferExprInstance(fun, tparams) diff --git a/test/files/pos/t6514.scala b/test/files/pos/t6514.scala new file mode 100644 index 0000000000..7c58605d39 --- /dev/null +++ b/test/files/pos/t6514.scala @@ -0,0 +1,11 @@ +object Test { + def e(msg: String) = new Exception(msg) + + // this code ain't dead. + def a(b: Boolean) = { + b match { + case true => throw e("true") + case false => throw e("false") + } + } +} |