Space: Cache space decomposition & other refactoring (#16937)

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -530,9 +530,12 @@ class Definitions {
   })
 
   @tu lazy val ListClass: Symbol       = requiredClass("scala.collection.immutable.List")
+  def ListType: TypeRef                = ListClass.typeRef
   @tu lazy val ListModule: Symbol      = requiredModule("scala.collection.immutable.List")
   @tu lazy val NilModule: Symbol       = requiredModule("scala.collection.immutable.Nil")
+  def NilType: TermRef                 = NilModule.termRef
   @tu lazy val ConsClass: Symbol       = requiredClass("scala.collection.immutable.::")
+  def ConsType: TypeRef                = ConsClass.typeRef
   @tu lazy val SeqFactoryClass: Symbol = requiredClass("scala.collection.SeqFactory")
 
   @tu lazy val SingletonClass: ClassSymbol =

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -2182,14 +2182,16 @@ object Types {
 
 // --- NamedTypes ------------------------------------------------------------------
 
-  abstract class NamedType extends CachedProxyType, ValueType { self =>
+  abstract class NamedType extends CachedProxyType, ValueType, Product { self =>
 
     type ThisType >: this.type <: NamedType
     type ThisName <: Name
 
     val prefix: Type
     def designator: Designator
     protected def designator_=(d: Designator): Unit
+    def _1: Type
+    def _2: Designator
 
     assert(NamedType.validPrefix(prefix), s"invalid prefix $prefix")
 
@@ -2931,6 +2933,7 @@ object Types {
     def apply(prefix: Type, designator: Name, denot: Denotation)(using Context): NamedType =
       if (designator.isTermName) TermRef.apply(prefix, designator.asTermName, denot)
       else TypeRef.apply(prefix, designator.asTypeName, denot)
+    def unapply(tp: NamedType): NamedType = tp
 
     def validPrefix(prefix: Type): Boolean = prefix.isValueType || (prefix eq NoPrefix)
   }

compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -2,11 +2,10 @@ package dotty.tools
 package dotc
 package transform
 
-import scala.annotation.tailrec
 import core._
 import MegaPhase._
-import collection.mutable
 import Symbols._, Contexts._, Types._, StdNames._, NameOps._
+import patmat.SpaceEngine
 import util.Spans._
 import typer.Applications.*
 import SymUtils._
@@ -16,9 +15,12 @@ import Decorators._
 import NameKinds.{PatMatStdBinderName, PatMatAltsName, PatMatResultName}
 import config.Printers.patmatch
 import reporting._
-import dotty.tools.dotc.ast._
+import ast._
 import util.Property._
 
+import scala.annotation.tailrec
+import scala.collection.mutable
+
 /** The pattern matching transform.
  *  After this phase, the only Match nodes remaining in the code are simple switches
  *  where every pattern is an integer or string constant
@@ -45,9 +47,8 @@ class PatternMatcher extends MiniPhase {
       val translated = new Translator(matchType, this).translateMatch(tree)
 
       // check exhaustivity and unreachability
-      val engine = new patmat.SpaceEngine
-      engine.checkExhaustivity(tree)
-      engine.checkRedundancy(tree)
+      SpaceEngine.checkExhaustivity(tree)
+      SpaceEngine.checkRedundancy(tree)
 
       translated.ensureConforms(matchType)
     }