backend: implement copying IR tree with variable declarations

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/common/DeepCopyIrTreeWithDeclarations.kt

@@ -0,0 +1,59 @@
+package org.jetbrains.kotlin.backend.common
+
+import org.jetbrains.kotlin.descriptors.*
+import org.jetbrains.kotlin.descriptors.impl.LocalVariableDescriptor
+import org.jetbrains.kotlin.ir.util.DeepCopyIrTree
+
+/**
+ * Copies IR tree with descriptors of all declarations inside;
+ * updates the references to these declarations.
+ */
+open class DeepCopyIrTreeWithDeclarations : DeepCopyIrTree() {
+
+    private fun DeclarationDescriptor.notSupported(): Nothing = TODO("${this}")
+
+    override fun mapModuleDescriptor(descriptor: ModuleDescriptor) = descriptor.notSupported()
+    override fun mapPackageFragmentDescriptor(descriptor: PackageFragmentDescriptor) = descriptor.notSupported()
+    override fun mapClassDeclaration(descriptor: ClassDescriptor) = descriptor.notSupported()
+    override fun mapTypeAliasDeclaration(descriptor: TypeAliasDescriptor) = descriptor.notSupported()
+    override fun mapFunctionDeclaration(descriptor: FunctionDescriptor) = descriptor.notSupported()
+    override fun mapConstructorDeclaration(descriptor: ClassConstructorDescriptor) = descriptor.notSupported()
+    override fun mapPropertyDeclaration(descriptor: PropertyDescriptor) = descriptor.notSupported()
+    override fun mapLocalPropertyDeclaration(descriptor: VariableDescriptorWithAccessors) = descriptor.notSupported()
+    override fun mapEnumEntryDeclaration(descriptor: ClassDescriptor) = descriptor.notSupported()
+
+    val copiedVariables = mutableMapOf<VariableDescriptor, VariableDescriptor>()
+
+    override fun mapVariableDeclaration(descriptor: VariableDescriptor): VariableDescriptor {
+        // TODO: how to ensure that the variable is not visible from outside of the transformed IR?
+
+        if (descriptor is VariableDescriptorWithAccessors && (descriptor.getter != null || descriptor.setter != null)) {
+            TODO("$descriptor with accessors")
+        }
+
+        val newDescriptor = LocalVariableDescriptor(
+                /* containingDeclaration = */ descriptor.containingDeclaration,
+                /* annotations = */ descriptor.annotations,
+                /* name = */ descriptor.name,
+                /* type = */ descriptor.type,
+                /* mutable = */ descriptor.isVar,
+                /* isDelegated = */ false,
+                /* source = */ descriptor.source
+        )
+
+        assert (descriptor !in copiedVariables)
+        copiedVariables[descriptor] = newDescriptor
+
+        return newDescriptor
+    }
+
+    // Note: the reference to a variable can be traversed only after the declaration of that variable,
+    // so it is correct to map only references whose descriptors have copies.
+    // However such approach can be incorrect when copying functions, classes etc.
+
+    override fun mapValueReference(descriptor: ValueDescriptor) =
+            copiedVariables[descriptor] ?: descriptor
+
+    override fun mapVariableReference(descriptor: VariableDescriptor) =
+            copiedVariables[descriptor] ?: descriptor
+}