Don't check opening quote in quotedByWithEscapes()

Author: fluentfuture

dot-parse/src/main/java/com/google/common/labs/parse/Parser.java

@@ -349,7 +349,7 @@ private static Parser<String> quotedBy(Parser<?> before, Parser<?> after) {
   }
 
   /**
-   * String literal quoted by {@code quoteChar} with backslash escapes.
+   * String literal quoted by {@code before} and {@code after} with backslash escapes.
    *
    * <p>When a backslash is encountered, the {@code escaped} parser is used to parse the escaped
    * character(s).
@@ -375,8 +375,6 @@ private static Parser<String> quotedBy(Parser<?> before, Parser<?> after) {
    */
   public static Parser<String> quotedByWithEscapes(
       char before, char after, Parser<? extends CharSequence> escaped) {
-    checkArgument(before != '\\', "quoteChar cannot be '\\'");
-    checkArgument(!Character.isISOControl(before), "quoteChar cannot be a control character");
     return quotedByWithEscapes(Character.toString(before), after, escaped);
   }
 

dot-parse/src/test/java/com/google/common/labs/parse/MiniSearchTest.java

@@ -67,7 +67,7 @@ static SearchCriteria parse(String input) {
       // A search term is either quoted, or unquoted (but cannot be a keyword)
       Parser<Term> unquoted =
           word().suchThat(w -> !keywords.contains(w), "search term").map(Term::new);
-      Parser<Term> quoted = Parser.quotedByWithEscapes('"', '"', (Parser<? extends CharSequence>) Parser.chars(1)).map(Term::new);
+      Parser<Term> quoted = Parser.quotedByWithEscapes('"', '"', Parser.chars(1)).map(Term::new);
 
       // Leaf-level search term can be a quoted, unquoted term, or a sub-criteria inside parentheses.
       // They are then grouped by the boolean operators.

dot-parse/src/test/java/com/google/common/labs/parse/ParserTest.java

@@ -450,14 +450,6 @@ public void quotedByWithEscapes_failures() {
 
   @Test
   public void quotedByWithEscapes_invalidQuoteChar_throws() {
-    assertThrows(
-        IllegalArgumentException.class, () -> Parser.quotedByWithEscapes('\\', '"', chars(1)));
-    assertThrows(
-        IllegalArgumentException.class, () -> Parser.quotedByWithEscapes('\n', '"', chars(1)));
-    assertThrows(
-        IllegalArgumentException.class, () -> Parser.quotedByWithEscapes('\r', '"', chars(1)));
-    assertThrows(
-        IllegalArgumentException.class, () -> Parser.quotedByWithEscapes('\t', '"', chars(1)));
     assertThrows(
         IllegalArgumentException.class, () -> Parser.quotedByWithEscapes('"', '\\', chars(1)));
     assertThrows(