more work for #549

src/main/java/com/fasterxml/jackson/core/JsonFactoryBuilder.java

@@ -198,6 +198,13 @@ public JsonFactoryBuilder highestNonEscapedChar(int maxNonEscaped) {
      * @param ch Character to use for quoting field names and JSON String values.
      */
     public JsonFactoryBuilder quoteChar(char ch) {
+        // 12-Aug-2019, tatu: Due to implementation details, escaping characters beyond
+        //    7-bit ASCII set has deep overhead so let's limit set. If we absolutely
+        //    must it is possible of course, but leads to problems combining with
+        //    custom escaping aspects.
+        if (ch > 0x7F) {
+            throw new IllegalArgumentException("Can only use Unicode characters up to 0x7F as quote characters");
+        }
         _quoteChar = ch;
         return this;
     }

src/test/java/com/fasterxml/jackson/core/json/CustomQuoteCharTest.java

@@ -12,6 +12,18 @@ public class CustomQuoteCharTest
             .quoteChar('\'')
             .build();
 
+    // Only ASCII range supported as of 2.10
+    public void testInvalidQuote() throws Exception
+    {
+        try {
+            streamFactoryBuilder()
+                .quoteChar('\u00A0');
+            fail("Should not allow quote character outside ASCII range");
+        } catch (IllegalArgumentException e) {
+            verifyException(e, "Can only use Unicode characters up to 0x7F");
+        }
+    }
+
     public void testBasicAposWithCharBased() throws Exception
     {
         StringWriter w;