[FIR JS] Report JS_MODULE-related diagnostics

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/utils/FirDeclarationUtil.kt

@@ -33,3 +33,13 @@ inline val FirDeclaration.isPrecompiled: Boolean
     get() = origin == FirDeclarationOrigin.Precompiled
 inline val FirDeclaration.isSynthetic: Boolean
     get() = origin == FirDeclarationOrigin.Synthetic
+
+// NB: This function checks transitive localness. That is,
+// if a declaration `isNonLocal`, then its parent also `isNonLocal`.
+val FirDeclaration.isNonLocal
+    get() = when (this) {
+        is FirFile -> true
+        is FirCallableDeclaration -> !symbol.callableId.isLocal
+        is FirClassLikeDeclaration -> !symbol.classId.isLocal
+        else -> false
+    }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/symbols/impl/FirFunctionSymbol.kt

@@ -104,6 +104,7 @@ class FirAnonymousFunctionSymbol : FirFunctionWithoutNameSymbol<FirAnonymousFunc
 class FirPropertyAccessorSymbol : FirFunctionWithoutNameSymbol<FirPropertyAccessor>(Name.identifier("accessor")) {
     val isGetter: Boolean get() = fir.isGetter
     val isSetter: Boolean get() = fir.isSetter
+    val propertySymbol get() = fir.propertySymbol
 }
 
 class FirErrorFunctionSymbol : FirFunctionWithoutNameSymbol<FirErrorFunction>(Name.identifier("error"))