KT-894 wrong string concatenation

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -1853,7 +1853,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                 value.put(lhsType, v);                                          // receiver lhs
                 final IntrinsicMethod intrinsic = (IntrinsicMethod) callable;
                 //noinspection NullableProblems
-                intrinsic.generate(this, v, lhsType, expression, Arrays.asList(expression.getRight()), null);
+                intrinsic.generate(this, v, lhsType, expression, Arrays.asList(expression.getRight()), StackValue.onStack(lhsType));
                 value.store(v);
             }
             else {

compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/Concat.java

@@ -2,6 +2,7 @@ package org.jetbrains.jet.codegen.intrinsics;
 
 import com.intellij.psi.PsiElement;
 import org.jetbrains.jet.codegen.ExpressionCodegen;
+import org.jetbrains.jet.codegen.JetTypeMapper;
 import org.jetbrains.jet.codegen.StackValue;
 import org.jetbrains.jet.lang.psi.JetExpression;
 import org.objectweb.asm.Type;
@@ -16,17 +17,18 @@ public class Concat implements IntrinsicMethod {
     @Override
     public StackValue generate(ExpressionCodegen codegen, InstructionAdapter v, Type expectedType, PsiElement element, List<JetExpression> arguments, StackValue receiver) {
         codegen.generateStringBuilderConstructor();
-        if (receiver == null) {                                    // LHS.plus(RHS)
+        if (receiver == null || receiver == StackValue.none()) {                                                     // LHS + RHS
+            codegen.invokeAppend(arguments.get(0));                                // StringBuilder(LHS)
+            codegen.invokeAppend(arguments.get(1));
+        }
+        else {                                    // LHS.plus(RHS)
             v.swap();                                                              // StringBuilder LHS
             codegen.invokeAppendMethod(expectedType);  // StringBuilder(LHS)
             codegen.invokeAppend(arguments.get(0));
         }
-        else {                                                     // LHS + RHS
+
-            codegen.invokeAppend(arguments.get(0));                                // StringBuilder(LHS)
-            codegen.invokeAppend(arguments.get(1));
-        }
-        
         v.invokevirtual("java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
-        return StackValue.onStack(Type.getObjectType("java/lang/String"));
+        StackValue.onStack(JetTypeMapper.JL_STRING_TYPE).put(expectedType, v);
+        return StackValue.onStack(expectedType);
     }
 }

compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/IntrinsicMethods.java

@@ -40,6 +40,7 @@ public class IntrinsicMethods {
     public static final IteratorNext ITERATOR_NEXT = new IteratorNext();
     public static final ArraySet ARRAY_SET = new ArraySet();
     public static final ArrayGet ARRAY_GET = new ArrayGet();
+    public static final StringPlus STRING_PLUS = new StringPlus();
 
     private final Project myProject;
     private final JetStandardLibrary myStdLib;
@@ -87,7 +88,7 @@ public class IntrinsicMethods {
         declareOverload(myStdLib.getLibraryScope().getFunctions("toString"), 0, new ToString());
         declareOverload(myStdLib.getLibraryScope().getFunctions("equals"), 1, EQUALS);
         declareOverload(myStdLib.getLibraryScope().getFunctions("identityEquals"), 1, EQUALS);
-        declareOverload(myStdLib.getLibraryScope().getFunctions("plus"), 1, new StringPlus());
+        declareOverload(myStdLib.getLibraryScope().getFunctions("plus"), 1, STRING_PLUS);
         declareOverload(myStdLib.getLibraryScope().getFunctions("Array"), 1, new NewArray());
         declareOverload(myStdLib.getLibraryScope().getFunctions("sure"), 0, new Sure());
         declareOverload(myStdLib.getLibraryScope().getFunctions("synchronized"), 1, new StupidSync());

compiler/backend/src/org/jetbrains/jet/codegen/intrinsics/StringPlus.java

@@ -20,8 +20,14 @@ import java.util.List;
 public class StringPlus implements IntrinsicMethod {
     @Override
     public StackValue generate(ExpressionCodegen codegen, InstructionAdapter v, Type expectedType, PsiElement element, List<JetExpression> arguments, StackValue receiver) {
-        codegen.gen(arguments.get(0)).put(JetTypeMapper.JL_STRING_TYPE, v);
+        if(receiver == null || receiver == StackValue.none()) {
-        codegen.gen(arguments.get(1)).put(JetTypeMapper.TYPE_OBJECT, v);
+            codegen.gen(arguments.get(0)).put(JetTypeMapper.JL_STRING_TYPE, v);
+            codegen.gen(arguments.get(1)).put(JetTypeMapper.TYPE_OBJECT, v);
+        }
+        else {
+            receiver.put(JetTypeMapper.JL_STRING_TYPE, v);
+            codegen.gen(arguments.get(0)).put(JetTypeMapper.TYPE_OBJECT, v);
+        }
         v.invokestatic("jet/runtime/Intrinsics", "stringPlus", "(Ljava/lang/String;Ljava/lang/Object;)Ljava/lang/String;");
         return StackValue.onStack(JetTypeMapper.JL_STRING_TYPE);
     }

compiler/testData/codegen/regressions/kt894.jet

@@ -0,0 +1,8 @@
+fun stringConcat(n : Int) : String? {
+  var string : String? = ""
+  for (i in 0..(n - 1))
+    string += "LOL "
+  return string
+}
+
+fun box() = if(stringConcat(3) == "LOL LOL LOL ") "OK" else "fail"

compiler/tests/org/jetbrains/jet/codegen/FunctionGenTest.java

@@ -17,50 +17,6 @@ public class FunctionGenTest extends CodegenTestCase {
 //        System.out.println(generateToText());
     }
 
-    public void testAnyToString () throws InvocationTargetException, IllegalAccessException {
-        loadText("fun foo(x: Any) = x.toString()");
-//        System.out.println(generateToText());
-        Method foo = generateFunction();
-        assertEquals("something", foo.invoke(null, "something"));
-        assertEquals("null", foo.invoke(null, new Object[]{null}));
-
-    }
-
-    public void testNullableAnyToString () throws InvocationTargetException, IllegalAccessException {
-        loadText("fun foo(x: Any?) = x.toString()");
-//        System.out.println(generateToText());
-        Method foo = generateFunction();
-        assertEquals("something", foo.invoke(null, "something"));
-        assertEquals("null", foo.invoke(null, new Object[]{null}));
-
-    }
-
-    public void testNullableStringPlus () throws InvocationTargetException, IllegalAccessException {
-        loadText("fun foo(x: String?, y: Any?) = x + y");
-        String text = generateToText();
-        assertTrue(text.contains(".stringPlus"));
-//        System.out.println(text);
-        Method foo = generateFunction();
-        assertEquals("something239", foo.invoke(null, "something", 239));
-        assertEquals("null239", foo.invoke(null, null, 239));
-        assertEquals("239null", foo.invoke(null, "239", null));
-        assertEquals("nullnull", foo.invoke(null, null, null));
-
-    }
-
-    public void testNonNullableStringPlus () throws InvocationTargetException, IllegalAccessException {
-        loadText("fun foo(x: String, y: Any?) = x + y + 120");
-        String text = generateToText();
-        assertFalse(text.contains(".stringPlus"));
-//        System.out.println(text);
-        Method foo = generateFunction();
-        assertEquals("something239120", foo.invoke(null, "something", 239));
-        assertEquals("null239120", foo.invoke(null, null, 239));
-        assertEquals("239null120", foo.invoke(null, "239", null));
-        assertEquals("nullnull120", foo.invoke(null, null, null));
-
-    }
-
     public void testAnyEqualsNullable () throws InvocationTargetException, IllegalAccessException {
         loadText("fun foo(x: Any?) = x.equals(\"lala\")");
 //        System.out.println(generateToText());

compiler/tests/org/jetbrains/jet/codegen/StringsTest.java

@@ -1,11 +1,58 @@
 package org.jetbrains.jet.codegen;
 
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
 /**
  * @author yole
  * @author alex.tkachman
  */
 public class StringsTest extends CodegenTestCase {
 
+    public void testAnyToString () throws InvocationTargetException, IllegalAccessException {
+        loadText("fun foo(x: Any) = x.toString()");
+//        System.out.println(generateToText());
+        Method foo = generateFunction();
+        assertEquals("something", foo.invoke(null, "something"));
+        assertEquals("null", foo.invoke(null, new Object[]{null}));
+
+    }
+
+    public void testNullableAnyToString () throws InvocationTargetException, IllegalAccessException {
+        loadText("fun foo(x: Any?) = x.toString()");
+//        System.out.println(generateToText());
+        Method foo = generateFunction();
+        assertEquals("something", foo.invoke(null, "something"));
+        assertEquals("null", foo.invoke(null, new Object[]{null}));
+
+    }
+
+    public void testNullableStringPlus () throws InvocationTargetException, IllegalAccessException {
+        loadText("fun foo(x: String?, y: Any?) = x + y");
+        String text = generateToText();
+        assertTrue(text.contains(".stringPlus"));
+//        System.out.println(text);
+        Method foo = generateFunction();
+        assertEquals("something239", foo.invoke(null, "something", 239));
+        assertEquals("null239", foo.invoke(null, null, 239));
+        assertEquals("239null", foo.invoke(null, "239", null));
+        assertEquals("nullnull", foo.invoke(null, null, null));
+
+    }
+
+    public void testNonNullableStringPlus () throws InvocationTargetException, IllegalAccessException {
+        loadText("fun foo(x: String, y: Any?) = x + y + 120");
+        String text = generateToText();
+        assertFalse(text.contains(".stringPlus"));
+//        System.out.println(text);
+        Method foo = generateFunction();
+        assertEquals("something239120", foo.invoke(null, "something", 239));
+        assertEquals("null239120", foo.invoke(null, null, 239));
+        assertEquals("239null120", foo.invoke(null, "239", null));
+        assertEquals("nullnull120", foo.invoke(null, null, null));
+
+    }
+
     public void testRawStrings() throws Exception {
         blackBoxFile("rawStrings.jet");
     }
@@ -13,4 +60,8 @@ public class StringsTest extends CodegenTestCase {
     public void testKt881() throws Exception {
         blackBoxFile("regressions/kt881.jet");
     }
+
+    public void testKt894() throws Exception {
+        blackBoxFile("regressions/kt894.jet");
+    }
 }