Fix unquoted string value in HOCON would cause infinite loop crash.

src/core/Akka.Tests/Configuration/HoconTests.cs

@@ -879,6 +879,43 @@ public void Can_parse_abbreviated_timespan2()
             var res = ConfigurationFactory.ParseString(hocon).GetTimeSpan("timespan");
             Assert.Equal(50, res.TotalMilliseconds);
         }
+
+        [Fact(Skip = "not working yet")]
+        public void Can_substitute_with_concated_string()
+        {
+            var hocon = @"
+    akka.cluster.name = cluster
+    akka.cluster.seed-node = ""akka.tcp://${akka.cluster.name}@127.0.0.1:4053""";
+
+            var config = ConfigurationFactory.ParseString(hocon);
+            var actual = config.GetString("akka.cluster.seed-node");
+            Console.Out.WriteLine($"RESULT:{actual}");
+            Assert.Equal("akka.tcp://cluster@127.0.0.1:4053", actual);
+        }
+
+        [Fact]
+        public void Can_parse_unquoted_string_list()
+        {
+            var hocon = @"hocon-array = [array-value-1, array-value-2]";
+            var config = ConfigurationFactory.ParseString(hocon);
+            var actual = config.GetStringList("hocon-array");
+            Assert.True(actual.Contains("array-value-1"));
+            Assert.True(actual.Contains("array-value-2"));
+        }
+
+        [Fact]
+        public void Should_throw_an_exception_when_parsing_invalid_unquoted_string()
+        {
+            var hocon = @"unquoted-string = akka.tcp://Cluster@127.0.0.1:4053";
+            Assert.Throws<ConfigurationException>(() => { ConfigurationFactory.ParseString(hocon); });
+        }
+
+        [Fact]
+        public void Should_throw_an_exception_when_parsing_invalid_unquoted_string_inside_array()
+        {
+            var hocon = @"akka.cluster.seed-nodes = [akka.tcp://Cluster@127.0.0.1:4053]";
+            Assert.Throws<ConfigurationException>(() => { ConfigurationFactory.ParseString(hocon); });
+        }
     }
 }
 

src/core/Akka/Configuration/Hocon/HoconTokenizer.cs

@@ -743,6 +743,14 @@ private Token PullUnquotedText()
                 sb.Append(Take());
             }
 
+            // Unquoted text does not support assignment character.
+            if (IsAssignment())
+                throw new ConfigurationException(
+                    @"Could not parse an unquoted text value containing assignment character '=' or ':'.
+- If you want to declare a new object, please enclose the item with curly brackets.
+- If you want to declare a URI address, please enclose the item with double quotes."
+                );
+
             return Token.LiteralValue(sb.ToString());
         }