Add new utility method: withAttachment

Author: odersky

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -849,8 +849,7 @@ object desugar {
           fwd
       }
       val moduleName = tdef.name.toTermName
-      val localRef = Select(Ident(moduleName), tdef.name)
-      localRef.pushAttachment(SuppressAccessCheck, ())
+      val localRef = Select(Ident(moduleName), tdef.name).withAttachment(SuppressAccessCheck, ())
       val aliasType = cpy.TypeDef(tdef)(rhs = completeForwarder(localRef)).withSpan(tdef.span.startPos)
       val localType = tdef.withMods(Modifiers(Synthetic | Opaque).withPrivateWithin(tdef.name))
 

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -259,10 +259,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     }
 
     /** Install the derived type tree as a dependency on `sym` */
-    def watching(sym: Symbol): this.type = {
-      pushAttachment(OriginalSymbol, sym)
-      this
-    }
+    def watching(sym: Symbol): this.type = withAttachment(OriginalSymbol, sym)
 
     /** A hook to ensure that all necessary symbols are completed so that
      *  OriginalSymbol attachments are propagated to this tree

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2426,7 +2426,7 @@ class Typer extends Namer
     def tryApply(implicit ctx: Context) = {
       val pt1 = pt.withContext(ctx)
       val sel = typedSelect(untpd.Select(untpd.TypedSplice(tree), nme.apply), pt1)
-      sel.pushAttachment(InsertedApply, ())
+        .withAttachment(InsertedApply, ())
       if (sel.tpe.isError) sel
       else try adapt(simplify(sel, pt1, locked), pt1, locked) finally sel.removeAttachment(InsertedApply)
     }

compiler/src/dotty/tools/dotc/util/Attachment.scala

@@ -101,6 +101,11 @@ object Attachment {
       this
     }
 
+    def withAttachment[V](key: Key[V], value: V): this.type = {
+      pushAttachment(key, value)
+      this
+    }
+
     final def pushAttachment[V](key: Key[V], value: V): Unit = {
       assert(!getAttachment(key).isDefined, s"duplicate attachment for key $key")
       next = new Link(key, value, next)