Fix diagnostics calculations for incremental analysis

idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/PerFileAnalysisCache.kt

@@ -261,9 +261,9 @@ private class StackedCompositeBindingContextTrace(
     /**
      * All diagnostics from parentContext apart those diagnostics those belongs to the element or its descendants
      */
-    val parentDiagnosticsApartElement: List<Diagnostic> = parentContext.diagnostics.all().filter { d ->
+    val parentDiagnosticsApartElement: Collection<Diagnostic> = parentContext.diagnostics.all().filter { d ->
         d.psiElement.parentsWithSelf.none { it == element }
-    }.toList()
+    }
 
     inner class StackedCompositeBindingContext : BindingContext {
         var cachedDiagnostics: Diagnostics? = null
@@ -279,9 +279,12 @@ private class StackedCompositeBindingContextTrace(
 
         override fun getDiagnostics(): Diagnostics {
             if (cachedDiagnostics == null) {
-                val diagnosticList =
-                    parentDiagnosticsApartElement + (this@StackedCompositeBindingContextTrace.mutableDiagnostics?.all() ?: emptyList())
-                cachedDiagnostics = MergedDiagnostics(diagnosticList, parentContext.diagnostics.modificationTracker)
+                val mergedDiagnostics = mutableSetOf<Diagnostic>()
+                mergedDiagnostics.addAll(parentDiagnosticsApartElement)
+                this@StackedCompositeBindingContextTrace.mutableDiagnostics?.all()?.let {
+                    mergedDiagnostics.addAll(it)
+                }
+                cachedDiagnostics = MergedDiagnostics(mergedDiagnostics, parentContext.diagnostics.modificationTracker)
             }
             return cachedDiagnostics!!
         }