Make Context#moreProperties strongly typed

To do this, factor out Key from Attachment into a new type, Property.Key.

9 files changed, 39 insertions, 26 deletions

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index edd6da5c9..4e27da2ca 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -8,7 +8,7 @@ import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._
 import Decorators._
 import language.higherKinds
 import collection.mutable.ListBuffer
-import util.Attachment
+import util.Property
 
 object desugar {
   import untpd._
@@ -16,7 +16,7 @@ object desugar {
   /** Tags a .withFilter call generated by desugaring a for expression.
    *  Such calls can alternatively be rewritten to use filter.
    */
-  val MaybeFilter = new Attachment.Key[Unit]
+  val MaybeFilter = new Property.Key[Unit]
 
   /** Info of a variable in a pattern: The named tree and its type */
   private type VarInfo = (NameTree, Tree)
diff --git a/src/dotty/tools/dotc/ast/Trees.scala b/src/dotty/tools/dotc/ast/Trees.scala
index bb6fbd5ba..3b5de9308 100644
--- a/src/dotty/tools/dotc/ast/Trees.scala
+++ b/src/dotty/tools/dotc/ast/Trees.scala
@@ -12,7 +12,7 @@ import collection.immutable.IndexedSeq
 import collection.mutable.ListBuffer
 import parsing.Tokens.Token
 import printing.Printer
-import util.{Stats, Attachment, DotClass}
+import util.{Stats, Attachment, Property, DotClass}
 import annotation.unchecked.uncheckedVariance
 import language.implicitConversions
 import parsing.Scanners.Comment
@@ -30,8 +30,8 @@ object Trees {
   /** The total number of created tree nodes, maintained if Stats.enabled */
   @sharable var ntrees = 0
 
-  /** Attachment key for trees with documentation strings attached */
-  val DocComment = new Attachment.Key[Comment]
+  /** Property key for trees with documentation strings attached */
+  val DocComment = new Property.Key[Comment]
 
    @sharable private var nextId = 0 // for debugging
 
diff --git a/src/dotty/tools/dotc/ast/untpd.scala b/src/dotty/tools/dotc/ast/untpd.scala
index 61c3a79a4..32e27e9c7 100644
--- a/src/dotty/tools/dotc/ast/untpd.scala
+++ b/src/dotty/tools/dotc/ast/untpd.scala
@@ -6,7 +6,7 @@ import core._
 import util.Positions._, Types._, Contexts._, Constants._, Names._, NameOps._, Flags._
 import Denotations._, SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._
 import Decorators._
-import util.Attachment
+import util.Property
 import language.higherKinds
 import collection.mutable.ListBuffer
 
@@ -161,17 +161,17 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     def derivedType(originalSym: Symbol)(implicit ctx: Context): Type
   }
 
-    /** Attachment key containing TypeTrees whose type is computed
+    /** Property key containing TypeTrees whose type is computed
    *  from the symbol in this type. These type trees have marker trees
    *  TypeRefOfSym or InfoOfSym as their originals.
    */
-  val References = new Attachment.Key[List[Tree]]
+  val References = new Property.Key[List[Tree]]
 
-  /** Attachment key for TypeTrees marked with TypeRefOfSym or InfoOfSym
+  /** Property key for TypeTrees marked with TypeRefOfSym or InfoOfSym
    *  which contains the symbol of the original tree from which this
    *  TypeTree is derived.
    */
-  val OriginalSymbol = new Attachment.Key[Symbol]
+  val OriginalSymbol = new Property.Key[Symbol]
 
   // ------ Creation methods for untyped only -----------------
 
diff --git a/src/dotty/tools/dotc/core/Contexts.scala b/src/dotty/tools/dotc/core/Contexts.scala
index d8beb4b5c..6f9d19c40 100644
--- a/src/dotty/tools/dotc/core/Contexts.scala
+++ b/src/dotty/tools/dotc/core/Contexts.scala
@@ -30,6 +30,7 @@ import config.{Settings, ScalaSettings, Platform, JavaPlatform, SJSPlatform}
 import language.implicitConversions
 import DenotTransformers.DenotTransformer
 import parsing.Scanners.Comment
+import util.Property.Key
 import xsbti.AnalysisCallback
 
 object Contexts {
@@ -177,9 +178,12 @@ object Contexts {
     def freshName(prefix: Name): String = freshName(prefix.toString)
 
     /** A map in which more contextual properties can be stored */
-    private var _moreProperties: Map[String, Any] = _
-    protected def moreProperties_=(moreProperties: Map[String, Any]) = _moreProperties = moreProperties
-    def moreProperties: Map[String, Any] = _moreProperties
+    private var _moreProperties: Map[Key[Any], Any] = _
+    protected def moreProperties_=(moreProperties: Map[Key[Any], Any]) = _moreProperties = moreProperties
+    def moreProperties: Map[Key[Any], Any] = _moreProperties
+
+    def property[T](key: Key[T]): Option[T] =
+      moreProperties.get(key).asInstanceOf[Option[T]]
 
     private var _typeComparer: TypeComparer = _
     protected def typeComparer_=(typeComparer: TypeComparer) = _typeComparer = typeComparer
@@ -459,9 +463,10 @@ object Contexts {
     def setTypeComparerFn(tcfn: Context => TypeComparer): this.type = { this.typeComparer = tcfn(this); this }
     def setSearchHistory(searchHistory: SearchHistory): this.type = { this.searchHistory = searchHistory; this }
     def setFreshNames(freshNames: FreshNameCreator): this.type = { this.freshNames = freshNames; this }
-    def setMoreProperties(moreProperties: Map[String, Any]): this.type = { this.moreProperties = moreProperties; this }
+    def setMoreProperties(moreProperties: Map[Key[Any], Any]): this.type = { this.moreProperties = moreProperties; this }
 
-    def setProperty(prop: (String, Any)): this.type = setMoreProperties(moreProperties + prop)
+    def setProperty[T](key: Key[T], value: T): this.type =
+      setMoreProperties(moreProperties.updated(key, value))
 
     def setPhase(pid: PhaseId): this.type = setPeriod(Period(runId, pid))
     def setPhase(phase: Phase): this.type = setPeriod(Period(runId, phase.start, phase.end))
diff --git a/src/dotty/tools/dotc/transform/ExplicitOuter.scala b/src/dotty/tools/dotc/transform/ExplicitOuter.scala
index 6a52b128c..60ef1b306 100644
--- a/src/dotty/tools/dotc/transform/ExplicitOuter.scala
+++ b/src/dotty/tools/dotc/transform/ExplicitOuter.scala
@@ -15,7 +15,7 @@ import ast.Trees._
 import SymUtils._
 import dotty.tools.dotc.ast.tpd
 import dotty.tools.dotc.core.Phases.Phase
-import util.Attachment
+import util.Property
 import collection.mutable
 
 /** This phase adds outer accessors to classes and traits that need them.
@@ -36,7 +36,7 @@ class ExplicitOuter extends MiniPhaseTransform with InfoTransformer { thisTransf
   import ExplicitOuter._
   import ast.tpd._
 
-  val Outer = new Attachment.Key[Tree]
+  val Outer = new Property.Key[Tree]
 
   override def phaseName: String = "explicitOuter"
 
diff --git a/src/dotty/tools/dotc/typer/Inliner.scala b/src/dotty/tools/dotc/typer/Inliner.scala
index 852689a75..4eb8588a6 100644
--- a/src/dotty/tools/dotc/typer/Inliner.scala
+++ b/src/dotty/tools/dotc/typer/Inliner.scala
@@ -18,7 +18,7 @@ import Annotations.Annotation
 import transform.ExplicitOuter
 import config.Printers.inlining
 import ErrorReporting.errorTree
-import util.Attachment
+import util.Property
 import collection.mutable
 
 object Inliner {
@@ -28,7 +28,7 @@ object Inliner {
     lazy val body = tree
   }
 
-  private val InlinedBody = new Attachment.Key[InlinedBody]
+  private val InlinedBody = new Property.Key[InlinedBody] // to be used as attachment
 
   def attachBody(inlineAnnot: Annotation, tree: => Tree)(implicit ctx: Context): Unit =
     inlineAnnot.tree.putAttachment(InlinedBody, new InlinedBody(tree))
diff --git a/src/dotty/tools/dotc/typer/Namer.scala b/src/dotty/tools/dotc/typer/Namer.scala
index 06e798bdb..4dff02018 100644
--- a/src/dotty/tools/dotc/typer/Namer.scala
+++ b/src/dotty/tools/dotc/typer/Namer.scala
@@ -9,7 +9,7 @@ import Contexts._, Symbols._, Types._, SymDenotations._, Names._, NameOps._, Fla
 import ast.desugar, ast.desugar._
 import ProtoTypes._
 import util.Positions._
-import util.{Attachment, SourcePosition, DotClass}
+import util.{Property, SourcePosition, DotClass}
 import collection.mutable
 import annotation.tailrec
 import ErrorReporting._
@@ -160,9 +160,9 @@ class Namer { typer: Typer =>
 
   import untpd._
 
-  val TypedAhead = new Attachment.Key[tpd.Tree]
-  val ExpandedTree = new Attachment.Key[Tree]
-  val SymOfTree = new Attachment.Key[Symbol]
+  val TypedAhead = new Property.Key[tpd.Tree]
+  val ExpandedTree = new Property.Key[Tree]
+  val SymOfTree = new Property.Key[Symbol]
 
   /** A partial map from unexpanded member and pattern defs and to their expansions.
    *  Populated during enterSyms, emptied during typer.
diff --git a/src/dotty/tools/dotc/util/Attachment.scala b/src/dotty/tools/dotc/util/Attachment.scala
index 8088b4cd0..20facfd97 100644
--- a/src/dotty/tools/dotc/util/Attachment.scala
+++ b/src/dotty/tools/dotc/util/Attachment.scala
@@ -4,9 +4,7 @@ package dotty.tools.dotc.util
  *  adding, removing and lookup of attachments. Attachments are typed key/value pairs.
  */
 object Attachment {
-
-  /** The class of keys for attachments yielding values of type V */
-  class Key[+V]
+  import Property.Key
 
   /** An implementation trait for attachments.
    *  Clients should inherit from Container instead.
diff --git a/src/dotty/tools/dotc/util/Property.scala b/src/dotty/tools/dotc/util/Property.scala
new file mode 100644
index 000000000..608fc88e6
--- /dev/null
+++ b/src/dotty/tools/dotc/util/Property.scala
@@ -0,0 +1,10 @@
+package dotty.tools.dotc.util
+
+/** Defines a key type with which to tag properties, such as attachments
+ *  or context properties
+ */
+object Property {
+
+  /** The class of keys for properties of type V */
+  class Key[+V]
+}
\ No newline at end of file