Don't treat string enum members as numbers. Fixes YousefED#186

Author: schani

test/programs/enums-string/main.ts

@@ -1,6 +1,7 @@
 enum Enum {
     X = "x" as any,
-    Y = "y" as any
+    Y = "y" as any,
+    Z = "123" as any
 }
 
 interface MyObject {

test/programs/enums-string/schema.json

@@ -3,6 +3,7 @@
     "definitions": {
         "Enum": {
             "enum": [
+                "123",
                 "x",
                 "y"
             ],

typescript-json-schema.ts

@@ -240,16 +240,16 @@ export class JsonSchemaGenerator {
         if (str === undefined) {
             str = (typ as any).text;
         }
-        if (typ.flags & ts.TypeFlags.EnumLiteral) {
+        if (typ.flags & ts.TypeFlags.StringLiteral) {
+            return str;
+        } else if (typ.flags & ts.TypeFlags.BooleanLiteral) {
+            return (typ as any).intrinsicName === "true";
+        } else if (typ.flags & ts.TypeFlags.EnumLiteral) {
             // or .text for old TS
             let num = parseFloat(str as string);
             return isNaN(num) ? str : num;
-        } else if (typ.flags & ts.TypeFlags.StringLiteral) {
-            return str;
         } else if (typ.flags & ts.TypeFlags.NumberLiteral) {
             return parseFloat(str as string);
-        } else if (typ.flags & ts.TypeFlags.BooleanLiteral) {
-            return (typ as any).intrinsicName === "true";
         }
         return undefined;
     }