1 files changed, 70 insertions, 0 deletions
diff --git a/test/junit/scala/tools/nsc/backend/jvm/StringConcatTest.scala b/test/junit/scala/tools/nsc/backend/jvm/StringConcatTest.scala
new file mode 100644
index 0000000000..80cde6c9a9
--- /dev/null
+++ b/test/junit/scala/tools/nsc/backend/jvm/StringConcatTest.scala
@@ -0,0 +1,70 @@
+package scala.tools.nsc
+package backend.jvm
+
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.junit.Test
+import scala.tools.asm.Opcodes._
+import org.junit.Assert._
+
+import scala.tools.testing.AssertUtil._
+
+import CodeGenTools._
+import scala.tools.partest.ASMConverters
+import ASMConverters._
+import scala.tools.testing.ClearAfterClass
+
+object StringConcatTest extends ClearAfterClass.Clearable {
+  var compiler = newCompiler()
+  def clear(): Unit = { compiler = null }
+}
+
+@RunWith(classOf[JUnit4])
+class StringConcatTest extends ClearAfterClass {
+  ClearAfterClass.stateToClear = StringConcatTest
+  val compiler = StringConcatTest.compiler
+
+  val commonPreInstructions = List(Label(0), LineNumber(1, Label(0)), TypeOp(NEW, "java/lang/StringBuilder"), Op(DUP), Invoke(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "()V", false), Ldc(LDC, "abc"), Invoke(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false), VarOp(ALOAD, 0))
+
+  val commonPostInstructions = List(Invoke(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false), Op(ARETURN), Label(12))
+
+  def instructionsWithCommonParts(instructions: List[Instruction]) = commonPreInstructions ++ instructions ++ commonPostInstructions
+
+  def instructionsForResultMethod(code: String): List[Instruction] = {
+    val methods = compileMethods(compiler)(code)
+    val resultMethod = methods.find(_.name == "result").get
+    instructionsFromMethod(resultMethod)
+  }
+
+  @Test
+  def concatStringToStringBuilder: Unit = {
+    val code = """ def string = "def"; def result = "abc" + string """
+    val actualInstructions = instructionsForResultMethod(code)
+    val expectedInstructions = instructionsWithCommonParts(List(Invoke(INVOKEVIRTUAL, "C", "string", "()Ljava/lang/String;", false), Invoke(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/String;)Ljava/lang/StringBuilder;", false)))
+    assertSameCode(actualInstructions, expectedInstructions)
+  }
+
+  @Test
+  def concatStringBufferToStringBuilder: Unit = {
+    val code = """ def stringBuffer = new java.lang.StringBuffer("def"); def result = "abc" + stringBuffer """
+    val actualInstructions = instructionsForResultMethod(code)
+    val expectedInstructions = instructionsWithCommonParts(List(Invoke(INVOKEVIRTUAL, "C", "stringBuffer", "()Ljava/lang/StringBuffer;", false), Invoke(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/StringBuffer;)Ljava/lang/StringBuilder;", false)))
+    assertSameCode(actualInstructions, expectedInstructions)
+  }
+
+  @Test
+  def concatCharSequenceToStringBuilder: Unit = {
+    val code = """ def charSequence: CharSequence = "def"; def result = "abc" + charSequence """
+    val actualInstructions = instructionsForResultMethod(code)
+    val expectedInstructions = instructionsWithCommonParts(List(Invoke(INVOKEVIRTUAL, "C", "charSequence", "()Ljava/lang/CharSequence;", false), Invoke(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/CharSequence;)Ljava/lang/StringBuilder;", false)))
+    assertSameCode(actualInstructions, expectedInstructions)
+  }
+
+  @Test
+  def concatIntToStringBuilder: Unit = {
+    val code = """ def int = 123; def result = "abc" + int """
+    val actualInstructions = instructionsForResultMethod(code)
+    val expectedInstructions = instructionsWithCommonParts(List(Invoke(INVOKEVIRTUAL, "C", "int", "()I", false), Invoke(INVOKESTATIC, "scala/runtime/BoxesRunTime", "boxToInteger", "(I)Ljava/lang/Integer;", false), Invoke(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(Ljava/lang/Object;)Ljava/lang/StringBuilder;", false)))
+    assertSameCode(actualInstructions, expectedInstructions)
+  }
+}