Rework as a Symbol#source fix

Author: milessabin

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

@@ -626,15 +626,27 @@ object Symbols {
     final def symbol(implicit ev: DontUseSymbolOnSymbol): Nothing = unsupported("symbol")
     type DontUseSymbolOnSymbol
 
-    final def source(implicit ctx: Context): SourceFile =
-      if (!defTree.isEmpty && !ctx.erasedTypes) defTree.source
-      else this match {
-        case cls: ClassSymbol => cls.sourceOfClass
-        case _ =>
-          if (denot.is(Module)) denot.moduleClass.source
-          else if (denot.exists) denot.owner.source
-          else NoSource
-      }
+    final def source(implicit ctx: Context): SourceFile = {
+      def valid(src: SourceFile): SourceFile =
+        if (src.exists && src.file.extension != "class") src
+        else NoSource
+
+      if (!denot.exists) NoSource
+      else
+        valid(defTree.source) match {
+          case NoSource =>
+            valid(denot.owner.source) match {
+              case NoSource =>
+                this match {
+                  case cls: ClassSymbol      => valid(cls.sourceOfClass)
+                  case _ if denot.is(Module) => valid(denot.moduleClass.source)
+                  case _ => NoSource
+                }
+              case src => src
+            }
+          case src => src
+        }
+    }
 
     /** A symbol related to `sym` that is defined in source code.
      *

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

@@ -12,7 +12,6 @@ import Decorators._
 import ast.Trees._
 import MegaPhase._
 import java.io.File.separatorChar
-import util.{ NoSource, SourceFile }
 
 import ValueClasses._
 
@@ -85,29 +84,10 @@ class ExpandPrivate extends MiniPhase with IdentityDenotTransformer { thisPhase
         (j < 0 || p1(j) == separatorChar)
       }
 
-      def findSource(sym: Symbol): SourceFile = {
-        def valid(src: SourceFile): Boolean = src.exists && src.file.extension != "class"
-
-        if(sym eq NoSymbol) NoSource
-        else {
-          val dTree = sym.defTree
-          if(valid(dTree.source)) dTree.source
-          else {
-            val oSrc = findSource(sym.owner)
-            if(oSrc.exists) oSrc
-            else if(valid(sym.source))
-              sym.source
-            else NoSource
-          }
-        }
-      }
-
-      val dSrc = findSource(d.symbol)
-      val cSrc = findSource(ctx.owner)
-
-      assert(dSrc.exists && cSrc.exists && isSimilar(dSrc.path, cSrc.path),
-          s"private ${d.symbol.showLocated} in ${dSrc} accessed from ${ctx.owner.showLocated} in ${cSrc}")
-
+      assert(d.symbol.source.exists &&
+             ctx.owner.source.exists &&
+             isSimilar(d.symbol.source.path, ctx.owner.source.path),
+          s"private ${d.symbol.showLocated} in ${d.symbol.source} accessed from ${ctx.owner.showLocated} in ${ctx.owner.source}")
       d.ensureNotPrivate.installAfter(thisPhase)
     }