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Compiler for the SubScript extension of the Scala Programming Language
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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Martin Odersky
*/
package scala.tools.nsc
package ast
import scala.reflect.ClassTag
import scala.reflect.internal.Flags.BYNAMEPARAM
import scala.reflect.internal.Flags.DEFAULTPARAM
import scala.reflect.internal.Flags.IMPLICIT
import scala.reflect.internal.Flags.PARAM
import scala.reflect.internal.Flags.PARAMACCESSOR
import scala.reflect.internal.Flags.PRESUPER
import scala.reflect.internal.Flags.TRAIT
import scala.compat.Platform.EOL
trait Trees extends scala.reflect.internal.Trees { self: Global =>
// --- additional cases --------------------------------------------------------
/** Only used during parsing */
case class Parens(args: List[Tree]) extends Tree
/** Documented definition, eliminated by analyzer */
case class DocDef(comment: DocComment, definition: Tree)
extends Tree {
override def symbol: Symbol = definition.symbol
override def symbol_=(sym: Symbol) { definition.symbol = sym }
override def isDef = definition.isDef
override def isTerm = definition.isTerm
override def isType = definition.isType
}
/** Array selection ` . ` only used during erasure */
case class SelectFromArray(qualifier: Tree, name: Name, erasure: Type)
extends RefTree with TermTree
/** Derived value class injection (equivalent to: `new C(arg)` after erasure); only used during erasure.
* The class `C` is stored as a tree attachment.
*/
case class InjectDerivedValue(arg: Tree)
extends SymTree with TermTree
class PostfixSelect(qual: Tree, name: Name) extends Select(qual, name)
/** emitted by typer, eliminated by refchecks */
case class TypeTreeWithDeferredRefCheck()(val check: () => TypeTree) extends TypTree
// --- factory methods ----------------------------------------------------------
/** Factory method for a primary constructor super call `super.(args_1)...(args_n)`
*/
def PrimarySuperCall(argss: List[List[Tree]]): Tree = argss match {
case Nil => Apply(gen.mkSuperInitCall, Nil)
case xs :: rest => rest.foldLeft(Apply(gen.mkSuperInitCall, xs): Tree)(Apply.apply)
}
/** Construct class definition with given class symbol, value parameters,
* supercall arguments and template body.
*
* @param sym the class symbol
* @param constrMods the modifiers for the class constructor, i.e. as in `class C private (...)`
* @param vparamss the value parameters -- if they have symbols they
* should be owned by `sym`
* @param body the template statements without primary constructor
* and value parameter fields.
*/
def ClassDef(sym: Symbol, constrMods: Modifiers, vparamss: List[List[ValDef]], body: List[Tree], superPos: Position): ClassDef = {
// "if they have symbols they should be owned by `sym`"
assert(mforall(vparamss)(_.symbol.owner == sym), (mmap(vparamss)(_.symbol), sym))
ClassDef(sym,
gen.mkTemplate(sym.info.parents map TypeTree,
if (sym.thisSym == sym || phase.erasedTypes) noSelfType else ValDef(sym.thisSym),
constrMods, vparamss, body, superPos))
}
// --- subcomponents --------------------------------------------------
object treeInfo extends {
val global: Trees.this.type = self
} with TreeInfo
// --- additional cases in operations ----------------------------------
override protected def xtraverse(traverser: Traverser, tree: Tree): Unit = tree match {
case Parens(ts) =>
traverser.traverseTrees(ts)
case DocDef(comment, definition) =>
traverser.traverse(definition)
case SelectFromArray(qualifier, selector, erasure) =>
traverser.traverse(qualifier)
case InjectDerivedValue(arg) =>
traverser.traverse(arg)
case TypeTreeWithDeferredRefCheck() =>
// (and rewrap the result? how to update the deferred check? would need to store wrapped tree instead of returning it from check)
case _ => super.xtraverse(traverser, tree)
}
trait TreeCopier extends super.InternalTreeCopierOps {
def DocDef(tree: Tree, comment: DocComment, definition: Tree): DocDef
def SelectFromArray(tree: Tree, qualifier: Tree, selector: Name, erasure: Type): SelectFromArray
def InjectDerivedValue(tree: Tree, arg: Tree): InjectDerivedValue
def TypeTreeWithDeferredRefCheck(tree: Tree): TypeTreeWithDeferredRefCheck
}
implicit val TreeCopierTag: ClassTag[TreeCopier] = ClassTag[TreeCopier](classOf[TreeCopier])
def newStrictTreeCopier: TreeCopier = new StrictTreeCopier
def newLazyTreeCopier: TreeCopier = new LazyTreeCopier
class StrictTreeCopier extends super.StrictTreeCopier with TreeCopier {
def DocDef(tree: Tree, comment: DocComment, definition: Tree) =
new DocDef(comment, definition).copyAttrs(tree)
def SelectFromArray(tree: Tree, qualifier: Tree, selector: Name, erasure: Type) =
new SelectFromArray(qualifier, selector, erasure).copyAttrs(tree)
def InjectDerivedValue(tree: Tree, arg: Tree) =
new InjectDerivedValue(arg).copyAttrs(tree)
def TypeTreeWithDeferredRefCheck(tree: Tree) = tree match {
case dc@TypeTreeWithDeferredRefCheck() => new TypeTreeWithDeferredRefCheck()(dc.check).copyAttrs(tree)
}
}
class LazyTreeCopier extends super.LazyTreeCopier with TreeCopier {
def DocDef(tree: Tree, comment: DocComment, definition: Tree) = tree match {
case t @ DocDef(comment0, definition0)
if (comment0 == comment) && (definition0 == definition) => t
case _ => this.treeCopy.DocDef(tree, comment, definition)
}
def SelectFromArray(tree: Tree, qualifier: Tree, selector: Name, erasure: Type) = tree match {
case t @ SelectFromArray(qualifier0, selector0, _)
if (qualifier0 == qualifier) && (selector0 == selector) => t
case _ => this.treeCopy.SelectFromArray(tree, qualifier, selector, erasure)
}
def InjectDerivedValue(tree: Tree, arg: Tree) = tree match {
case t @ InjectDerivedValue(arg0)
if (arg0 == arg) => t
case _ => this.treeCopy.InjectDerivedValue(tree, arg)
}
def TypeTreeWithDeferredRefCheck(tree: Tree) = tree match {
case t @ TypeTreeWithDeferredRefCheck() => t
case _ => this.treeCopy.TypeTreeWithDeferredRefCheck(tree)
}
}
class Transformer extends super.Transformer {
def transformUnit(unit: CompilationUnit) {
try unit.body = transform(unit.body)
catch {
case ex: Exception =>
log(supplementErrorMessage("unhandled exception while transforming "+unit))
throw ex
}
}
}
// used when a phase is disabled
object noopTransformer extends Transformer {
override def transformUnit(unit: CompilationUnit): Unit = {}
}
override protected def xtransform(transformer: super.Transformer, tree: Tree): Tree = tree match {
case DocDef(comment, definition) =>
transformer.treeCopy.DocDef(tree, comment, transformer.transform(definition))
case SelectFromArray(qualifier, selector, erasure) =>
transformer.treeCopy.SelectFromArray(
tree, transformer.transform(qualifier), selector, erasure)
case InjectDerivedValue(arg) =>
transformer.treeCopy.InjectDerivedValue(
tree, transformer.transform(arg))
case TypeTreeWithDeferredRefCheck() =>
transformer.treeCopy.TypeTreeWithDeferredRefCheck(tree)
}
object resetPos extends Traverser {
override def traverse(t: Tree) {
if (t != EmptyTree) t.setPos(NoPosition)
super.traverse(t)
}
}
// Finally, noone resetAllAttrs it anymore, so I'm removing it from the compiler.
// Even though it's with great pleasure I'm doing that, I'll leave its body here to warn future generations about what happened in the past.
//
// So what actually happened in the past is that we used to have two flavors of resetAttrs: resetAllAttrs and resetLocalAttrs.
// resetAllAttrs destroyed all symbols and types in the tree in order to reset its state to something suitable for retypechecking
// and/or embedding into bigger trees / different lexical scopes. (Btw here's some background on why people would want to use
// reset attrs in the first place: https://groups.google.com/forum/#!topic/scala-internals/TtCTPlj_qcQ).
//
// However resetAllAttrs was more of a poison than of a treatment, because along with locally defined symbols that are the cause
// for almost every or maybe even every case of tree corruption, it erased external bindings that sometimes could not be restored.
// This is how we came up with resetLocalAttrs that left external bindings alone, and that was a big step forward.
// Then slowly but steadily we've evicted all usages of resetAllAttrs from our codebase in favor of resetLocalAttrs
// and have been living happily ever after.
//
// def resetAllAttrs(x: Tree, leaveAlone: Tree => Boolean = null): Tree = new ResetAttrs(localOnly = false, leaveAlone).transform(x)
// upd. Unfortunately this didn't work out quite as we expected. The last two users of resetAllAttrs:
// reification and typedLabelDef broke in very weird ways when we replaced resetAllAttrs with resetLocalAttrs
// (see SI-8316 change from resetAllAttrs to resetLocalAttrs in reifiers broke Slick and
// SI-8318 NPE in mixin in scala-continuations for more information).
// Given that we're supposed to release 2.11.0-RC1 in less than a week, I'm temporarily reinstating resetAllAttrs
// until we have time to better understand what's going on. In order to dissuade people from using it,
// it now comes with a new, ridiculous name.
/** @see ResetAttrs */
def brutallyResetAttrs(x: Tree, leaveAlone: Tree => Boolean = null): Tree = new ResetAttrs(brutally = true, leaveAlone).transform(x)
/** @see ResetAttrs */
def resetAttrs(x: Tree): Tree = new ResetAttrs(brutally = false, leaveAlone = null).transform(x)
/** A transformer which resets symbol and tpe fields of all nodes in a given tree,
* with special treatment of:
* TypeTree nodes: are replaced by their original if it exists, otherwise tpe field is reset
* to empty if it started out empty or refers to local symbols (which are erased).
* TypeApply nodes: are deleted if type arguments end up reverted to empty
* This(pkg) nodes where pkg is a package: these are kept.
*
* (bq:) This transformer has mutable state and should be discarded after use
*/
private class ResetAttrs(brutally: Boolean, leaveAlone: Tree => Boolean) {
// this used to be based on -Ydebug, but the need for logging in this code is so situational
// that I've reverted to a hard-coded constant here.
val debug = false
val trace = scala.tools.nsc.util.trace when debug
val locals = util.HashSet[Symbol](8)
val orderedLocals = scala.collection.mutable.ListBuffer[Symbol]()
def registerLocal(sym: Symbol) {
if (sym != null && sym != NoSymbol) {
if (debug && !(locals contains sym)) orderedLocals append sym
locals addEntry sym
}
}
class MarkLocals extends self.Traverser {
def markLocal(tree: Tree) {
if (tree.symbol != null && tree.symbol != NoSymbol) {
val sym = tree.symbol
registerLocal(sym)
registerLocal(sym.sourceModule)
registerLocal(sym.moduleClass)
registerLocal(sym.companionClass)
registerLocal(sym.companionModule)
registerLocal(sym.deSkolemize)
sym match {
case sym: TermSymbol => registerLocal(sym.referenced)
case _ => ;
}
}
}
override def traverse(tree: Tree) = {
tree match {
case _: DefTree | Function(_, _) | Template(_, _, _) =>
markLocal(tree)
case _ =>
tree
}
super.traverse(tree)
}
}
class Transformer extends self.Transformer {
override def transform(tree: Tree): Tree = {
if (leaveAlone != null && leaveAlone(tree))
tree
else
super.transform {
tree match {
case tree if !tree.canHaveAttrs =>
tree
case tpt: TypeTree =>
if (tpt.original != null)
transform(tpt.original)
else {
val refersToLocalSymbols = tpt.tpe != null && (tpt.tpe exists (tp => locals contains tp.typeSymbol))
val isInferred = tpt.wasEmpty
if (refersToLocalSymbols || isInferred) {
tpt.duplicate.clearType()
} else {
tpt
}
}
// If one of the type arguments of a TypeApply gets reset to an empty TypeTree, then this means that:
// 1) It isn't empty now (tpt.tpe != null), but it was empty before (tpt.wasEmpty).
// 2) Thus, its argument got inferred during a preceding typecheck.
// 3) Thus, all its arguments were inferred (because scalac can only infer all or nothing).
// Therefore, we can safely erase the TypeApply altogether and have it inferred once again in a subsequent typecheck.
// UPD: Actually there's another reason for erasing a type behind the TypeTree
// is when this type refers to symbols defined in the tree being processed.
// These symbols will be erased, because we can't leave alive a type referring to them.
// Here we can only hope that everything will work fine afterwards.
case TypeApply(fn, args) if args map transform exists (_.isEmpty) =>
transform(fn)
case EmptyTree =>
tree
case _ =>
val dupl = tree.duplicate
// Typically the resetAttrs transformer cleans both symbols and types.
// However there are exceptions when we cannot erase symbols due to idiosyncrasies of the typer.
// vetoXXX local variables declared below describe the conditions under which we cannot erase symbols.
//
// The first reason to not erase symbols is the threat of non-idempotency (SI-5464).
// Here we take care of references to package classes (SI-5705).
// There are other non-idempotencies, but they are not worked around yet.
//
// The second reason has to do with the fact that resetAttrs needs to be less destructive.
// Erasing locally-defined symbols is useful to prevent tree corruption, but erasing external bindings is not,
// therefore we want to retain those bindings, especially given that restoring them can be impossible
// if we move these trees into lexical contexts different from their original locations.
if (dupl.hasSymbol) {
val sym = dupl.symbol
val vetoScope = !brutally && !(locals contains sym) && !(locals contains sym.deSkolemize)
val vetoThis = dupl.isInstanceOf[This] && sym.isPackageClass
if (!(vetoScope || vetoThis)) dupl.symbol = NoSymbol
}
dupl.clearType()
}
}
}
}
def transform(x: Tree): Tree = {
new MarkLocals().traverse(x)
if (debug) {
assert(locals.size == orderedLocals.size)
val msg = orderedLocals.toList filter {_ != NoSymbol} map {" " + _} mkString EOL
trace("locals (%d total): %n".format(orderedLocals.size))(msg)
}
new Transformer().transform(x)
}
}
/* New pattern matching cases:
case Parens(expr) (only used during parsing)
case DocDef(comment, defn) => (eliminated by typer)
case TypeTreeWithDeferredRefCheck() => (created and eliminated by typer)
case SelectFromArray(_, _, _) => (created and eliminated by erasure)
case InjectDerivedValue(_) => (created and eliminated by erasure)
*/
}