IR: remove FakeOverrideCopier.makeExternal

Make the declaration external at the call site instead of creating two
instances of FakeOverrideCopier. It's possible because IR elements are
mutable, in particular isExternal is a var.

Maybe the same should be done to IrUnimplementedOverridesStrategy, but
that is postponed for another time.

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/overrides/CopyIrTreeWithSymbolsForFakeOverrides.kt

@@ -28,16 +28,20 @@ class CopyIrTreeWithSymbolsForFakeOverrides(
     private val parent: IrClass,
     unimplementedOverridesStrategy: IrUnimplementedOverridesStrategy
 ) {
+    private val symbolRemapper = FakeOverrideSymbolRemapperImpl(typeArguments, NullDescriptorsRemapper)
+
+    private val copier = FakeOverrideCopier(
+        symbolRemapper,
+        FakeOverrideTypeRemapper(symbolRemapper, typeArguments),
+        SymbolRenamer.DEFAULT,
+        parent,
+        unimplementedOverridesStrategy
+    )
+
     fun copy(): IrOverridableMember {
-        // Create new symbols.
         overridableMember.acceptVoid(symbolRemapper)
 
-        // Make symbol remapper aware of the callsite's type arguments.
-        // Copy IR.
-        val result = overridableMember.transform(
-            if (parent.isEffectivelyExternal()) copierMakingExternal else copier,
-            data = null
-        ) as IrOverridableMember
+        val result = overridableMember.transform(copier, null) as IrOverridableMember
 
         result.patchDeclarationParents(parent)
 
@@ -93,9 +97,7 @@ class CopyIrTreeWithSymbolsForFakeOverrides(
     private class FakeOverrideSymbolRemapperImpl(
         private val typeArguments: Map<IrTypeParameterSymbol, IrType>,
         descriptorsRemapper: DescriptorsRemapper
-    ) :
-        DeepCopySymbolRemapper(descriptorsRemapper) {
-
+    ) : DeepCopySymbolRemapper(descriptorsRemapper) {
         override fun getReferencedClassifier(symbol: IrClassifierSymbol): IrClassifierSymbol {
             val result = super.getReferencedClassifier(symbol)
             if (result !is IrTypeParameterSymbol)
@@ -104,30 +106,6 @@ class CopyIrTreeWithSymbolsForFakeOverrides(
         }
     }
 
-    private val symbolRemapper =
-        FakeOverrideSymbolRemapperImpl(
-            typeArguments,
-            NullDescriptorsRemapper
-        )
-
-    private val copier = FakeOverrideCopier(
-        symbolRemapper,
-        FakeOverrideTypeRemapper(symbolRemapper, typeArguments),
-        SymbolRenamer.DEFAULT,
-        makeExternal = false,
-        parent,
-        unimplementedOverridesStrategy
-    )
-
-    private val copierMakingExternal = FakeOverrideCopier(
-        symbolRemapper,
-        FakeOverrideTypeRemapper(symbolRemapper, typeArguments),
-        SymbolRenamer.DEFAULT,
-        makeExternal = true,
-        parent,
-        unimplementedOverridesStrategy
-    )
-
     private companion object {
         // TODO: RawTypeAnnotation, FlexibleMutability, EnhancedNullability?
         val TYPE_ANNOTATIONS_TO_MERGE = listOf(

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/overrides/FakeOverrideBuilderStrategy.kt

@@ -103,8 +103,22 @@ fun buildFakeOverrideMember(
     return CopyIrTreeWithSymbolsForFakeOverrides(member, substitutionMap, clazz, unimplementedOverridesStrategy)
         .copy()
         .apply {
+            makeExternal(clazz.isExternal)
+
             val isInvisible = isPrivateToThisModule(clazz, classifier.owner, friendModules)
             if (isInvisible && !member.annotations.hasAnnotation(StandardNames.FqNames.publishedApi))
                 visibility = DescriptorVisibilities.INVISIBLE_FAKE
         }
 }
+
+// TODO: this is JS-specific functionality which should be moved out of the common ir.tree.
+private fun IrOverridableMember.makeExternal(value: Boolean) {
+    when (this) {
+        is IrSimpleFunction -> isExternal = value
+        is IrProperty -> {
+            isExternal = value
+            getter?.isExternal = value
+            setter?.isExternal = value
+        }
+    }
+}

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/overrides/FakeOverrideCopier.kt

@@ -13,7 +13,6 @@ class FakeOverrideCopier(
     private val symbolRemapper: SymbolRemapper,
     private val typeRemapper: TypeRemapper,
     private val symbolRenamer: SymbolRenamer,
-    private val makeExternal: Boolean,
     private val parent: IrClass,
     private val unimplementedOverridesStrategy: IrUnimplementedOverridesStrategy
 ) : DeepCopyIrTreeWithSymbols(symbolRemapper, typeRemapper, symbolRenamer) {
@@ -35,7 +34,7 @@ class FakeOverrideCopier(
             isSuspend = declaration.isSuspend,
             isOperator = declaration.isOperator,
             isInfix = declaration.isInfix,
-            isExternal = makeExternal,
+            isExternal = declaration.isExternal,
         ).apply {
             transformAnnotations(declaration)
             copyTypeParametersFrom(declaration)
@@ -82,7 +81,7 @@ class FakeOverrideCopier(
             isLateinit = declaration.isLateinit,
             isDelegated = declaration.isDelegated,
             isExpect = declaration.isExpect,
-            isExternal = makeExternal
+            isExternal = declaration.isExternal,
         ).apply {
             transformAnnotations(declaration)
             this.getter = declaration.getter?.transform()