Extracted method.

compiler/backend/src/org/jetbrains/jet/codegen/CodegenUtil.java

@@ -17,6 +17,8 @@
 package org.jetbrains.jet.codegen;
 
 import com.intellij.openapi.util.Condition;
+import com.intellij.openapi.util.io.FileUtil;
+import com.intellij.psi.PsiFile;
 import com.intellij.util.containers.ContainerUtil;
 import com.intellij.util.containers.Stack;
 import org.jetbrains.annotations.NotNull;
@@ -286,4 +288,10 @@ public class CodegenUtil {
 
         return ((ImplementationBodyCodegen) classBodyCodegen.getParentCodegen());
     }
+
+    static int getPathHashCode(@NotNull PsiFile file) {
+        // Conversion to system-dependent name seems to be unnecessary, but it's hard to check now:
+        // it was introduced when fixing KT-2839, which appeared again (KT-3639).
+        return FileUtil.toSystemDependentName(file.getVirtualFile().getPath()).hashCode();
+    }
 }

compiler/backend/src/org/jetbrains/jet/codegen/NamespaceCodegen.java

@@ -273,12 +273,9 @@ public class NamespaceCodegen extends MemberCodegen {
     private static String getMultiFileNamespaceInternalName(@NotNull String namespaceInternalName, @NotNull PsiFile file) {
         String fileName = FileUtil.getNameWithoutExtension(PathUtil.getFileName(file.getName()));
 
-        // Conversion to system-dependent name seems to be unnecessary, but it's hard to check now:
-        // it was introduced when fixing KT-2839, which appeared again (KT-3639).
-        String pathHashCode = Integer.toHexString(FileUtil.toSystemDependentName(file.getVirtualFile().getPath()).hashCode());
-
         // path hashCode to prevent same name / different path collision
-        return namespaceInternalName + "$src$" + replaceSpecialSymbols(fileName) + "$" + pathHashCode;
+        return namespaceInternalName + "$src$" + replaceSpecialSymbols(fileName) + "$" + Integer.toHexString(
+                CodegenUtil.getPathHashCode(file));
     }
 
     private static String replaceSpecialSymbols(@NotNull String str) {