Creating an ANTLR grammar for Dart, potentially the syntax spec.

tools/spec_parser/SpecParser.java

Index: tools/spec_parser/SpecParser.java
diff --git a/tools/spec_parser/SpecParser.java b/tools/spec_parser/SpecParser.java
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+++ b/tools/spec_parser/SpecParser.java
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+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import org.antlr.runtime.*;
+
+/// Class for `main` which will parse files given as command line arguments.
+public class SpecParser {
+  static boolean verbose = false;
+
+  public static void main(String[] args) throws Exception {
+    if (args.length == 0) {
+      System.err.println("Expected a file path as argument.");
+      System.exit(1);
+    }
+    for (int i = 0; i < args.length; i++) {
+      String filePath = args[i];
+      if (filePath.equals("--verbose")) {
+        verbose = true;
+        continue;
+      }
+      CharStream charStream = new ANTLRFileStream(filePath);
+      DartLexer lexer = new DartLexer(charStream);
+      CommonTokenStream tokens = new CommonTokenStream(lexer);
+      DartParser parser = new DartParser(tokens);
+      DartParser.filePath = filePath;
+      DartParser.filePathHasBeenPrinted = false;
+      if (verbose) System.err.println(">>> Parsing file: " + filePath);
+      parser.libraryDefinition();
+    }
+  }
+}