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[Deprecated] exhaustivity & redundancy check for pattern matching #1261

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[Deprecated] exhaustivity & redundancy check for pattern matching #1261

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5cdd42f
initial works
liufengyun May 11, 2016
9a0952c
support check java enum from classfile and source file
liufengyun May 24, 2016
fd1b286
fix false warning about Nil
liufengyun Jun 2, 2016
d681a78
suppress checking of for, try and partial functions
liufengyun Jun 3, 2016
da9511d
add GADT test
liufengyun Jun 11, 2016
89e8ff9
refine patmat check for type erasure
liufengyun Jun 11, 2016
b25e952
add tuple test to patmat check
liufengyun Jun 12, 2016
e2db834
add test t5440 for patmat check
liufengyun Jun 13, 2016
2d6e803
better warning for higher-kinded types and alias types
liufengyun Jun 15, 2016
f69b305
fix SI-9657 about type bounds
liufengyun Jun 23, 2016
c79181d
address counter-example of two unrelated traits
liufengyun Jul 3, 2016
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initial works
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@liufengyun
liufengyun committed Jul 5, 2016
commit 5cdd42f3fd4cb6faa8670b53ead6a1e7fce062f1
10 changes: 10 additions & 0 deletions src/dotty/tools/dotc/transform/PatternMatcher.scala
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Expand Up @@ -50,8 +50,17 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
private var _id = 0 // left for debuging

override def transformMatch(tree: Match)(implicit ctx: Context, info: TransformerInfo): Tree = {
val Match(sel, cases) = tree

val translated = new Translator()(ctx).translator.translateMatch(tree)

// check exhaustivity and unreachability
val engine = new SpaceEngine
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@DarkDimius DarkDimius Jul 1, 2016

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PatternMatcher now has a 🌠SpaceEngine🌠 and can do interstellar travels. Looking forward to battle space invaders.
👾👾👾👾

if (!engine.skipCheck(sel.tpe)) {
engine.exhaustivity(tree)
engine.redundancy(tree)
}

translated.ensureConforms(tree.tpe)
}

Expand Down Expand Up @@ -1275,6 +1284,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer {thisTrans
case _ => (cases, None)
}


// checkMatchVariablePatterns(nonSyntheticCases) // only used for warnings

// we don't transform after uncurry
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9 changes: 9 additions & 0 deletions src/dotty/tools/dotc/transform/PostTyper.scala
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Expand Up @@ -38,6 +38,8 @@ import Symbols._, TypeUtils._
*
* (9) Adds SourceFile annotations to all top-level classes and objects
*
* (10) Adds Child annotations to all sealed classes
*
* The reason for making this a macro transform is that some functions (in particular
* super and protected accessors and instantiation checks) are naturally top-down and
* don't lend themselves to the bottom-up approach of a mini phase. The other two functions
Expand Down Expand Up @@ -231,6 +233,13 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisTran
ctx.compilationUnit.source.exists &&
sym != defn.SourceFileAnnot)
sym.addAnnotation(Annotation.makeSourceFile(ctx.compilationUnit.source.file.path))

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@DarkDimius DarkDimius Jul 1, 2016

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If we're unlucky, this will conflict with #1343.

if (!sym.isAnonymousClass) // ignore anonymous class
for (parent <- sym.asClass.classInfo.classParents) {
val pclazz = parent.classSymbol
if (pclazz.is(Sealed)) pclazz.addAnnotation(Annotation.makeChild(sym))
}

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@liufengyun liufengyun May 20, 2016

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Anonymous classes caused pickling-related error for tests/run/t8611b.scala:

https://gist.github.com/liufengyun/f4aca0853e06f96c9130a0a05bfa0d4f

If I ignore anonymous classes, then it works:

              if (!sym.isAnonymousClass) // ignore anonymous class
                for (parent <- sym.asClass.classInfo.classParents) {
                  val pclazz = parent.classSymbol
                  if (pclazz.is(Sealed)) pclazz.addAnnotation(Annotation.makeChild(sym))
                }

The problem is that ignore anonymous classes would make the algorithm silent in case it should report a warning:

sealed trait A
case class B() extends A
case class C() extends A

object M {
  val x = new A {}

  x match {
     case _: B => true
     case _: C => true
  }
}

Any ideas, @odersky @smarter ?

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@smarter smarter May 20, 2016 •
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If a sealed trait has direct anonymous subclasses then it's impossible to pattern match on all subclasses. I think the simplest solution is to disallow direct anonymous subclasses of sealed traits.

tree
}
else {
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