Avoid using Parser.sequence() in Production, it allocates objects

Author: fluentfuture

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

@@ -1043,8 +1043,13 @@ public final Parser<T> suchThat(Predicate<? super T> condition, String name) {
     };
   }
 
+  @Override public Parser<T> followedBy(Parser<?> suffix) {
+    requireNonNull(suffix);
+    return flatMap(v -> suffix.thenReturn(v));
+  }
+
   @Override public final <S> Parser<T> followedBy(Parser<S>.OrEmpty suffix) {
-    return sequence(this, suffix, (value, unused) -> value);
+    return followedBy(suffix.asUnsafeZeroWidthParser());
   }
 
   /**
@@ -1512,6 +1517,10 @@ public <S> Parser<S> then(Parser<S> suffix) {
       return sequence(this, suffix, (a, b) -> b);
     }
 
+    @Override public Parser<T> followedBy(Parser<?> suffix) {
+      return asUnsafeZeroWidthParser().followedBy(suffix);
+    }
+
     /** The current optional (or zero-or-more) parser may optionally be followed by {@code suffix}.  */
     @Override public <S> Parser<T>.OrEmpty followedBy(Parser<S>.OrEmpty suffix) {
       return sequence(this, suffix, (a, b) -> a);
@@ -1905,7 +1914,7 @@ static int skipIfAny(Parser<?> skip, CharInput input, int start) {
     };
   }
 
-  static <T> Parser<T> allowZeroWidth(Production<T> production) {
+  private static <T> Parser<T> allowZeroWidth(Production<T> production) {
     return switch (production) {
       case Parser<T> parser -> parser;
       case Parser<T>.OrEmpty orEmpty -> orEmpty.asUnsafeZeroWidthParser();

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

@@ -51,7 +51,7 @@ default Parser<T> between(String prefix, String suffix) {
 
   /** The current production must be enclosed between non-empty {@code prefix} and {@code suffix}. */
   default Parser<T> between(Parser<?> prefix, Parser<?> suffix) {
-    return Parser.sequence(prefix, this, (p, t) -> t).followedBy(suffix);
+    return prefix.then(this.followedBy(suffix));
   }
 
   /**
@@ -70,7 +70,7 @@ default Parser<T> between(Parser<?> prefix, Parser<?> suffix) {
    * {@code zeroOrMore(isNot('"')).immediatelyBetween("\"", "\"")}.
    */
   default Parser<T> immediatelyBetween(String prefix, String suffix) {
-    return Parser.string(prefix).then(Parser.literally(followedBy(suffix)));
+    return Parser.string(prefix).then(Parser.literally(this.followedBy(suffix)));
   }
 
   /**
@@ -92,9 +92,7 @@ default Parser<T> followedBy(String suffix) {
   }
 
   /** The current production must be followed by non-empty {@code suffix}. */
-  default Parser<T> followedBy(Parser<?> suffix) {
-    return Parser.sequence(Parser.allowZeroWidth(this), suffix, (a, b) -> a);
-  }
+  Parser<T> followedBy(Parser<?> suffix);
 
   /**
    * The current production may optionally be followed by {@code suffix}.