New J2K: Add string.length conversion

j2k/newSrc/org/jetbrains/kotlin/j2k/ConversionsRunner.kt

@@ -62,6 +62,7 @@ object ConversionsRunner {
             +CollectionOperationsConversion(context)
             +ArrayOperationsConversion(context)
             +TypeMappingConversion(context)
+            +StringMethodsConversion(context)
 
             //Kotlin --> Kotlin conversions
             +InnerClassConversion()

j2k/newSrc/org/jetbrains/kotlin/j2k/conversions/StringMethodsConversion.kt

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.j2k.conversions
+
+import org.jetbrains.kotlin.j2k.ConversionContext
+import org.jetbrains.kotlin.j2k.tree.*
+import org.jetbrains.kotlin.j2k.tree.impl.JKFieldAccessExpressionImpl
+
+
+class StringMethodsConversion(private val context: ConversionContext) : RecursiveApplicableConversionBase() {
+    override fun applyToElement(element: JKTreeElement): JKTreeElement {
+        if (element !is JKQualifiedExpression) return recurse(element)
+        val receiverType = element.receiver.type(context) ?: return recurse(element)
+        if (!receiverType.isStringType()) return recurse(element)
+
+        convertLengthCall(element.selector)?.also {
+            element.selector = it
+        }
+
+        return recurse(element)
+    }
+
+    private fun convertLengthCall(selector: JKExpression): JKFieldAccessExpressionImpl? {
+        if (selector !is JKMethodCallExpression) return null
+        return if (selector.identifier.name == "length") {
+            JKFieldAccessExpressionImpl(context.symbolProvider.provideByFqName("kotlin.String.length"))
+        } else null
+    }
+}

j2k/newSrc/org/jetbrains/kotlin/j2k/tree/types.kt

@@ -168,6 +168,9 @@ fun JKType.isCollectionType(symbolProvider: JKSymbolProvider): Boolean {
     return this.isSubtypeOf(collectionType, symbolProvider)
 }
 
+fun JKType.isStringType(): Boolean =
+    (this as? JKClassType)?.classReference?.name == "String"
+
 fun JKLiteralExpression.LiteralType.toPrimitiveType(): JKJavaPrimitiveType? =
     when (this) {
         JKLiteralExpression.LiteralType.CHAR -> JKJavaPrimitiveTypeImpl.CHAR