enhancements in character constant parsing

* missing assertion converted to ErrorValue
* added test for 'a
* '\' must be error (KT-461)

compiler/frontend/src/org/jetbrains/jet/lang/resolve/constants/CompileTimeConstantResolver.java

@@ -164,14 +164,21 @@ public class CompileTimeConstantResolver {
         if (error != null) {
             return error;
         }
-        assert text.charAt(0) == '\'' && text.charAt(text.length() - 1) == '\'';
+
+        if (text.charAt(0) != '\'' || text.charAt(text.length() - 1) != '\'') {
+            return new ErrorValue("Incorret character constant");
+        }
 
         text = text.substring(1, text.length() - 1);
 
         if (text.length() == 0) {
             return new ErrorValue("Empty character literal");
         } else if (text.length() == 1) {
-            return new CharValue(text.charAt(0));
+            if (text.charAt(0) == '\\') {
+                return new ErrorValue("Illegal escape: " + text);
+            } else {
+                return new CharValue(text.charAt(0));
+            }
         } else if (text.length() == 2 && text.charAt(0) == '\\') {
             Character escaped = translateEscape(text.charAt(1));
             if (escaped == null) {

compiler/testData/checkerWithErrorTypes/quick/IncorrectCharacterLiterals.jet

@@ -4,6 +4,9 @@
 fun ff() {
     val b = <!ERROR_COMPILE_TIME_VALUE!>''<!>
     val c = <!ERROR_COMPILE_TIME_VALUE!>'23'<!>
+    val d = <!ERROR_COMPILE_TIME_VALUE!>'a<!>
+    val e = <!ERROR_COMPILE_TIME_VALUE!>'ab<!>
+    val f = <!ERROR_COMPILE_TIME_VALUE!>'\'<!>
 }
 
 fun test() {
@@ -20,4 +23,4 @@ fun test() {
     <!ERROR_COMPILE_TIME_VALUE!>'\123'<!>
     <!ERROR_COMPILE_TIME_VALUE!>'\ra'<!>
     <!ERROR_COMPILE_TIME_VALUE!>'\000'<!>
-}
+}