Adopt scala's scheme for root import hiding

scalac hides a root import from Predef if there is an eplicit Predef import.
We now do the same (previously we did this only if the overriding import undefined
something, using a `x => _` syntax). To avoid cycles and races one had to be very careful
not to force import symbols too early, so we now compare the name before the symbol proper.

All this is likely temporary - the comment of ImportInfo#unimported points to a different,
more systematic solution.

1 files changed, 8 insertions, 3 deletions

diff --git a/compiler/src/dotty/tools/dotc/typer/Namer.scala b/compiler/src/dotty/tools/dotc/typer/Namer.scala
index 1b6e437b5..068ef3e4b 100644
--- a/compiler/src/dotty/tools/dotc/typer/Namer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Namer.scala
@@ -373,8 +373,13 @@ class Namer { typer: Typer =>
   }
 
   /** A new context that summarizes an import statement */
-  def importContext(sym: Symbol, selectors: List[Tree])(implicit ctx: Context) =
-    ctx.fresh.setImportInfo(new ImportInfo(sym, selectors))
+  def importContext(imp: Import, sym: Symbol)(implicit ctx: Context) = {
+    val impNameOpt = imp.expr match {
+      case ref: RefTree => Some(ref.name.asTermName)
+      case _            => None
+    }
+    ctx.fresh.setImportInfo(new ImportInfo(sym, imp.selectors, impNameOpt))
+  }
 
   /** A new context for the interior of a class */
   def inClassContext(selfInfo: DotClass /* Should be Type | Symbol*/)(implicit ctx: Context): Context = {
@@ -423,7 +428,7 @@ class Namer { typer: Typer =>
         setDocstring(pkg, stat)
         ctx
       case imp: Import =>
-        importContext(createSymbol(imp), imp.selectors)
+        importContext(imp, createSymbol(imp))
       case mdef: DefTree =>
         val sym = enterSymbol(createSymbol(mdef))
         setDocstring(sym, origStat)