KT-3652: Char is converted to Int when used inside string interpolation

#KT-3652 Fixed

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

@@ -354,8 +354,8 @@ public class AsmUtil {
         v.invokevirtual("java/lang/StringBuilder", "append", "(" + type.getDescriptor() + ")Ljava/lang/StringBuilder;");
     }
 
-    public static StackValue genToString(InstructionAdapter v, StackValue receiver) {
-        Type type = stringValueOfOrStringBuilderAppendType(receiver.type);
+    public static StackValue genToString(InstructionAdapter v, StackValue receiver, Type receiverType) {
+        Type type = stringValueOfOrStringBuilderAppendType(receiverType);
         receiver.put(type, v);
         v.invokestatic("java/lang/String", "valueOf", "(" + type.getDescriptor() + ")Ljava/lang/String;");
         return StackValue.onStack(JAVA_STRING_TYPE);

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

@@ -1173,7 +1173,8 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
         JetStringTemplateEntry[] entries = expression.getEntries();
 
         if (entries.length == 1 && entries[0] instanceof JetStringTemplateEntryWithExpression) {
-            return genToString(v, gen(entries[0].getExpression()));
+            JetExpression expr = entries[0].getExpression();
+            return genToString(v, gen(expr), expressionType(expr));
         }
 
         for (JetStringTemplateEntry entry : entries) {

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

@@ -40,6 +40,6 @@ public class ToString implements IntrinsicMethod {
             StackValue receiver,
             @NotNull GenerationState state
     ) {
-        return genToString(v, receiver);
+        return genToString(v, receiver, receiver.type);
     }
 }