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Fix #2772: Special case Devalify for java.lang.System.* #2781

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Merged
merged 7 commits into from
Jun 25, 2017
Merged

Fix #2772: Special case Devalify for java.lang.System.* #2781

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be8bcee
Fix #2772: Special case Devalify for java.lang.System.*
OlivierBlanvillain Jun 19, 2017
f4c19d9
Slight Devalify refactorings
OlivierBlanvillain Jun 19, 2017
faa8864
Indentation
OlivierBlanvillain Jun 19, 2017
cd035b2
Factor out isMutable logic, use it in DropGoodCasts
OlivierBlanvillain Jun 19, 2017
f824164
Document that local optimisations assumes final fields are final
OlivierBlanvillain Jun 19, 2017
cf54051
Adress review
OlivierBlanvillain Jun 20, 2017
09d4a8c
Use symbol.owner
OlivierBlanvillain Jun 21, 2017
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33 changes: 18 additions & 15 deletions compiler/src/dotty/tools/dotc/transform/localopt/Devalify.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -164,7 +164,17 @@ class Devalify extends Optimisation {
case _ => t
}

def readingOnlyVals(t: Tree)(implicit ctx: Context): Boolean = dropCasts(t) match {
def readingOnlyVals(t: Tree)(implicit ctx: Context): Boolean = {
def isGetterOfAImmutableField = t.symbol.isGetter && !t.symbol.is(Mutable)
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Of An ImmutableField

def isCaseClassWithVar = t.symbol.info.decls.exists(_.is(Mutable))
def isAccessingProductField = t.symbol.exists &&
t.symbol.owner.derivesFrom(defn.ProductClass) &&
t.symbol.owner.is(CaseClass) &&
t.symbol.name.isSelectorName &&
!isCaseClassWithVar // Conservatively covers case class A(var x: Int)
def isImmutableCaseAccessor = t.symbol.is(CaseAccessor) && !t.symbol.is(Mutable)

dropCasts(t) match {
case Typed(exp, _) => readingOnlyVals(exp)

case TypeApply(fun @ Select(rec, _), List(tp)) =>
Expand All @@ -173,29 +183,21 @@ class Devalify extends Optimisation {
else false

case Apply(Select(rec, _), Nil) =>
def isGetterOfAImmutableField = t.symbol.isGetter && !t.symbol.is(Mutable)
def isCaseClassWithVar = t.symbol.info.decls.exists(_.is(Mutable))
def isAccessingProductField = t.symbol.exists &&
t.symbol.owner.derivesFrom(defn.ProductClass) &&
t.symbol.owner.is(CaseClass) &&
t.symbol.name.isSelectorName &&
!isCaseClassWithVar // Conservative Covers case class A(var x: Int)
def isImmutableCaseAccessor = t.symbol.is(CaseAccessor) && !t.symbol.is(Mutable)
if (isGetterOfAImmutableField || isAccessingProductField || isImmutableCaseAccessor)
readingOnlyVals(rec)
else false

case Select(rec, _) if t.symbol.is(Method) =>
if (t.symbol.isGetter && !t.symbol.is(Mutable))
readingOnlyVals(rec) // getter of a immutable field
else if (t.symbol.owner.derivesFrom(defn.ProductClass) && t.symbol.owner.is(CaseClass) && t.symbol.name.isSelectorName) {
if (isGetterOfAImmutableField)
readingOnlyVals(rec) // Getter of an immutable field
else if (isAccessingProductField) {
def isImmutableField = {
val fieldId = t.symbol.name.toString.drop(1).toInt - 1
!t.symbol.owner.caseAccessors(ctx)(fieldId).is(Mutable)
}
if (isImmutableField) readingOnlyVals(rec) // accessing a field of a product
if (isImmutableField) readingOnlyVals(rec) // Accessing a field of a product
else false
} else if (t.symbol.is(CaseAccessor) && !t.symbol.is(Mutable))
} else if (isImmutableCaseAccessor)
readingOnlyVals(rec)
else false

Expand All @@ -208,7 +210,7 @@ class Devalify extends Optimisation {
} else
readingOnlyVals(qual)

case t: Ident if !t.symbol.is(Mutable) && !t.symbol.is(Method) && !t.symbol.info.dealias.isInstanceOf[ExprType] =>
case t: Ident if !t.symbol.is(Mutable | Method) && !t.symbol.info.dealias.isInstanceOf[ExprType] =>
desugarIdent(t) match {
case Some(t) => readingOnlyVals(t)
case None => true
Expand All @@ -228,5 +230,6 @@ class Devalify extends Optimisation {
case Literal(Constant(null)) => false
case t: Literal => true
case _ => false
}
}
}