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[PROOF-OF-CONCEPT/DO NOT MERGE] Avoid forcing type aliases to get their typeParams #981

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[PROOF-OF-CONCEPT/DO NOT MERGE] Avoid forcing type aliases to get their typeParams #981

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22 changes: 19 additions & 3 deletions src/dotty/tools/dotc/core/TypeApplications.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,8 @@ import util.Positions.Position
import config.Printers._
import collection.mutable
import java.util.NoSuchElementException
import ast.untpd.TypeDef
import typer.Namer

object TypeApplications {

Expand Down Expand Up @@ -63,7 +65,14 @@ class TypeApplications(val self: Type) extends AnyVal {
case self: TypeRef =>
val tsym = self.typeSymbol
if (tsym.isClass) tsym.typeParams
else if (tsym.isAliasType) self.underlying.typeParams
else if (tsym.isAliasType) {
tsym.infoOrCompleter match {
case c: Namer#Completer =>
c.typeParams(tsym)
case _ =>
self.underlying.typeParams
}
}
else {
val lam = LambdaClass(forcing = false)
if (lam.exists) lam.typeParams else Nil
Expand Down Expand Up @@ -200,6 +209,13 @@ class TypeApplications(val self: Type) extends AnyVal {
case nil => tp
}

def canForce(sym: Symbol) = sym.infoOrCompleter match {
case c: Namer#Completer =>
!sym.isAliasType
case _ =>
true
}

/** Instantiate type `tp` with `args`.
* @param original The original type for which we compute the type parameters
* This makes a difference for refinement types, because
Expand All @@ -209,7 +225,7 @@ class TypeApplications(val self: Type) extends AnyVal {
def instantiate(tp: Type, original: Type): Type = tp match {
case tp: TypeRef =>
val tsym = tp.symbol
if (tsym.isAliasType) tp.underlying.appliedTo(args)
if (tsym.isAliasType && canForce(tsym)) tp.underlying.appliedTo(args)
else {
val safeTypeParams =
if (tsym.isClass || !tp.typeSymbol.isCompleting) original.typeParams
Expand Down Expand Up @@ -242,7 +258,7 @@ class TypeApplications(val self: Type) extends AnyVal {
case tp: TypeRef =>
val sym = tp.symbol
if (sym.isClass) sym.isLambdaTrait
else !sym.isAliasType || isKnownHK(tp.info)
else !sym.isAliasType || !canForce(sym) || isKnownHK(tp.info)
case tp: TypeProxy => isKnownHK(tp.underlying)
case _ => false
}
Expand Down
26 changes: 23 additions & 3 deletions src/dotty/tools/dotc/typer/Namer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -478,6 +478,8 @@ class Namer { typer: Typer =>

/** The completer of a symbol defined by a member def or import (except ClassSymbols) */
class Completer(val original: Tree)(implicit ctx: Context) extends LazyType {
var completedParams: Boolean = false
var nestedCtx: Context = null

protected def localContext(owner: Symbol) = ctx.fresh.setOwner(owner).setTree(original)

Expand All @@ -491,7 +493,9 @@ class Namer { typer: Typer =>
typer1.defDefSig(original, sym)(localContext(sym).setTyper(typer1))
case original: TypeDef =>
assert(!original.isClassDef)
typeDefSig(original, sym)(localContext(sym).setNewScope)
if (nestedCtx == null)
nestedCtx = localContext(sym).setNewScope
typeDefSig(original, sym, completedParams)(nestedCtx)
case imp: Import =>
try {
val expr1 = typedAheadExpr(imp.expr, AnySelectionProto)
Expand All @@ -503,6 +507,21 @@ class Namer { typer: Typer =>
}
}

def typeParams(sym: Symbol) = original match {
case tdef: TypeDef =>
if (nestedCtx == null)
nestedCtx = localContext(sym).setNewScope

{
implicit val ctx: Context = nestedCtx
if (!completedParams) {
completeParams(tdef.tparams)
completedParams = true
}
tdef.tparams map (symbolOfTree(_).asType)
}
}

final override def complete(denot: SymDenotation)(implicit ctx: Context) = {
if (completions != noPrinter && ctx.typerState != this.ctx.typerState) {
completions.println(completions.getClass.toString)
Expand Down Expand Up @@ -807,8 +826,9 @@ class Namer { typer: Typer =>
else valOrDefDefSig(ddef, sym, typeParams, paramSymss, wrapMethType)
}

def typeDefSig(tdef: TypeDef, sym: Symbol)(implicit ctx: Context): Type = {
completeParams(tdef.tparams)
def typeDefSig(tdef: TypeDef, sym: Symbol, completedParams: Boolean)(implicit ctx: Context): Type = {
if (!completedParams)
completeParams(tdef.tparams)
val tparamSyms = tdef.tparams map symbolOfTree
val isDerived = tdef.rhs.isInstanceOf[untpd.DerivedTypeTree]
//val toParameterize = tparamSyms.nonEmpty && !isDerived
Expand Down