Namer#createCompanionLinks: avoid using denotNamed

The previous commit introduced two new usages of `denotNamed` which broke
tests/run/t1987b because `denotNamed` indirectly calls `packageObj`
which caches the package object, except that at this point the package
object is not yet entered, so the cache was incorrect. We fix this by
using `effectiveScope.lookup` instead since we only need to look into
the current scope, this is also true for the two existing usage of
`denotNamed` in `createCompanionLinks` so they were also replaced by
`effectiveScope.lookup`.

Author: smarter

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

@@ -570,8 +570,8 @@ class Namer { typer: Typer =>
 
     /** Create links between companion object and companion class */
     def createLinks(classTree: TypeDef, moduleTree: TypeDef)(implicit ctx: Context) = {
-      val claz = ctx.denotNamed(classTree.name.encode).symbol
-      val modl = ctx.denotNamed(moduleTree.name.encode).symbol
+      val claz = ctx.effectiveScope.lookup(classTree.name.encode)
+      val modl = ctx.effectiveScope.lookup(moduleTree.name.encode)
       ctx.synthesizeCompanionMethod(nme.COMPANION_CLASS_METHOD, claz, modl).entered
       ctx.synthesizeCompanionMethod(nme.COMPANION_MODULE_METHOD, modl, claz).entered
     }
@@ -613,10 +613,10 @@ class Namer { typer: Typer =>
       // example where this matters.
       if (ctx.owner.is(PackageClass)) {
         for (cdef @ TypeDef(moduleName, _) <- moduleDef.values) {
-          val moduleSym = ctx.denotNamed(moduleName.encode).symbol
+          val moduleSym = ctx.effectiveScope.lookup(moduleName.encode)
           if (moduleSym.isDefinedInCurrentRun) {
             val className = moduleName.stripModuleClassSuffix.toTypeName
-            val classSym = ctx.denotNamed(className.encode).symbol
+            val classSym = ctx.effectiveScope.lookup(className.encode)
             if (!classSym.isDefinedInCurrentRun) {
               val absentClassSymbol = ctx.newClassSymbol(ctx.owner, className, EmptyFlags, _ => NoType)
               enterSymbol(absentClassSymbol)