Fix #4185: Do not check names for modules that will not be emitted

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -207,8 +207,11 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
           }
         }
         checkName(claszSymbol)
-        if (int.symHelper(claszSymbol).isModuleClass)
-          checkName(claszSymbol.companionModule)
+        if (int.symHelper(claszSymbol).isModuleClass) {
+          val companionModule = claszSymbol.companionModule
+          if (int.symHelper(companionModule.owner).isPackageClass)
+            checkName(companionModule)
+        }
 
         // -------------- mirror class, if needed --------------
         val mirrorC =

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -59,6 +59,7 @@ class CompilationTests extends ParallelTesting {
     compileFile("tests/pos-special/i3323b.scala", defaultOptions.and("-Xfatal-warnings")) +
     compileFile("tests/pos-special/i3589-b.scala", defaultOptions.and("-Xfatal-warnings")) +
     compileFile("tests/pos-special/i4166.scala", defaultOptions.and("-Xfatal-warnings")) +
+    compileFile("tests/pos-special/i4185.scala", defaultOptions.and("-Xfatal-warnings")) +
     compileFile("tests/pos-special/completeFromSource/Test.scala", defaultOptions.and("-sourcepath", "tests/pos-special")) +
     compileFile("tests/pos-special/completeFromSource/Test2.scala", defaultOptions.and("-sourcepath", "tests/pos-special")) +
     compileFile("tests/pos-special/completeFromSource/Test3.scala", defaultOptions.and("-sourcepath", "tests/pos-special", "-scansource")) +

tests/pos-special/i4185.scala

@@ -0,0 +1,4 @@
+object ord {
+  class Ord
+  object Ord
+}