Throw if the phone-context parameter appears before the tel: prefix.

java/libphonenumber/src/com/google/i18n/phonenumbers/PhoneNumberUtil.java

@@ -3232,9 +3232,8 @@ public class PhoneNumberUtil {
     int numberEnd = numberToParse.indexOf(";", numberStart);
 
     if (numberEnd < 0) {
-      // If there is no semicolon, we assume the rest of the string is the national number.
-      // This should not happen, since we expect to find a semicolon if there is a phone-context.
-      numberEnd = numberToParse.length();
+      throw new NumberParseException(NumberParseException.ErrorType.NOT_A_NUMBER,
+          "The string supplied did not seem to be a phone number.");
     }
 
     String numberPart = numberToParse.substring(numberStart, numberEnd);

java/libphonenumber/test/com/google/i18n/phonenumbers/PhoneNumberUtilTest.java

@@ -2954,6 +2954,9 @@ public class PhoneNumberUtilTest extends TestMetadataTestCase {
     assertThrowsForInvalidPhoneContext("tel:033316005;phone-context=3phone");
     assertThrowsForInvalidPhoneContext("tel:033316005;phone-context=a-.nz");
     assertThrowsForInvalidPhoneContext("tel:033316005;phone-context=a{b}c");
+
+    // The phone-context parameter comes before the phone number.
+    assertThrowsForInvalidPhoneContext(";phone-context=+64;tel:03-331-6005");
   }
 
   private void assertThrowsForInvalidPhoneContext(String numberToParse) {