added a few experimental alternatives implementations of string templates for string/html/jdbc etc for KT-1565 seems there's a few ways we could do it...

libraries/testlib/test/template/experiment1/HtmlTemplateTest.kt

@@ -0,0 +1,31 @@
+package template.experiment1
+
+import kotlin.template.experiment1.*
+import kotlin.test.assertEquals
+import kotlin.dom.toXmlString
+
+import junit.framework.TestCase
+import org.w3c.dom.Node
+
+
+class HtmlTemplateTest : TestCase() {
+    fun testTemplate(): Unit {
+        val foo = "James"
+        val bar = "x > 1"
+
+        // Code generated by the following template expression:
+        //
+        // val actual = toHtml("<h1>$foo</h1> <p>hey $bar</p>")
+        val actual = toHtml{
+            it.text("<h1>")
+            it.expression(foo)
+            it.text("</h1> <p>hey ")
+            it.expression(bar)
+            it.text("</p>")
+        }
+
+        assertEquals("<h1>James</h1> <p>hey x &gt; 1</p>", actual)
+
+        println("Generated HTML: $actual")
+    }
+}

libraries/testlib/test/template/experiment1/StringTemplateTest.kt

@@ -0,0 +1,24 @@
+package template.experiment1
+
+import kotlin.template.experiment1.*
+import kotlin.test.assertEquals
+
+import junit.framework.TestCase
+
+class StringTemplateTest : TestCase() {
+    fun testTemplate() : Unit {
+        val name = "James"
+
+        // Code generated by the following template expression:
+        //
+        // val actual = format("hello $name!")
+        val actual = format{
+            it.text("hello ")
+            it.expression(name)
+            it.text("!")
+        }
+
+        println("Got text: $actual")
+        assertEquals("hello James!", actual)
+    }
+}

libraries/testlib/test/template/experiment2/HtmlTemplateTest.kt

@@ -0,0 +1,20 @@
+package test.template.experiment
+
+import kotlin.template.experiment2.*
+import kotlin.test.assertEquals
+
+import junit.framework.TestCase
+
+class HtmlTemplateTest : TestCase() {
+    fun testTemplate(): Unit {
+        val foo = "James"
+        val bar = "x > 1"
+
+        // Code generated by the following template expression:
+        //
+        // val actual = "<h1>$foo</h1> <p>hey $bar</p>".toHtml()
+        val actual = StringTemplate(array("<h1>", "</h1> <p>hey ", "</p>"), array(foo, bar)).toHtml()
+
+        assertEquals("<h1>James</h1> <p>hey x &gt; 1</p>", actual)
+    }
+}

libraries/testlib/test/template/experiment2/StringTemplateTest.kt

@@ -0,0 +1,19 @@
+package test.template.experiment
+
+import kotlin.template.experiment2.*
+import kotlin.test.assertEquals
+
+import junit.framework.TestCase
+
+class StringTemplateTest : TestCase() {
+    fun testTemplate(): Unit {
+        val name = "James"
+
+        // Code generated by the following template expression:
+        //
+        // val actual = "hello $name!".toString()
+        val actual = StringTemplate(array("hello ", "!"), array(name)).toString()
+
+        assertEquals("hello James!", actual)
+    }
+}

libraries/testlib/test/template/experiment3/HtmlTemplateTest.kt

@@ -1,9 +1,10 @@
 package test.template
 
-import junit.framework.TestCase
-import kotlin.template.*
+import kotlin.template.experiment3.*
 import kotlin.test.assertEquals
 
+import junit.framework.TestCase
+
 class HtmlTemplateTest : TestCase() {
     fun testTemplate(): Unit {
         val foo = "James"

libraries/testlib/test/template/experiment3/StringTemplateTest.kt

@@ -1,9 +1,10 @@
 package test.template
 
-import junit.framework.TestCase
-import kotlin.template.StringTemplate
+import kotlin.template.experiment3.*
 import kotlin.test.assertEquals
 
+import junit.framework.TestCase
+
 class StringTemplateTest : TestCase() {
     fun testTemplate(): Unit {
         val name = "James"

libraries/testlib/test/template/experiment4/Experiment4.kt

@@ -0,0 +1,52 @@
+package template.experiment4
+
+import junit.framework.TestCase
+import kotlin.test.assertEquals
+import kotlin.test.todo
+
+
+/**
+ * Creates a string template from some constant string expressions and some dynamic expressions.
+ */
+class StringTemplate<T>(val constantText : Array<String>, val fn : (T) -> Unit) {
+}
+
+fun StringBuilder.text(value : String) : Unit {
+    this.append(value)
+}
+
+fun StringBuilder.expression(value : Any?) : Unit {
+    this.append(value)
+}
+
+/**
+ * Converts a [[StringTemplate]] to a String
+ */
+fun toString(template : StringTemplate<StringBuilder>) : String {
+    val builder = StringBuilder()
+    template.fn(builder)
+    return builder.toString() ?: ""
+}
+
+class StringTemplateTest : TestCase() {
+    fun testTemplate() : Unit {
+        val name = "James"
+
+        // Code generated by the following template expression:
+        //
+        // val actual = "hello $name!"
+        val template = StringTemplate<StringBuilder>(array("hello ", "!"), { (it : StringBuilder) ->
+            println("About to apply function!")
+            it.text("hello ")
+            it.expression(name)
+            it.text("!")
+        })
+        println("Template has constants ${template.constantText.toList()} and function ${template.fn}")
+
+        todo {
+            val actual = toString(template)
+
+            assertEquals("hello James!", actual)
+        }
+    }
+}