Add maps syntax support

Change-Id: I7a01d3f541e7601da62763fe6860a4f4c49444c5

com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/bugs/MapSyntaxTest.java

diff --git a/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/bugs/MapSyntaxTest.java b/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/bugs/MapSyntaxTest.java
new file mode 100644
index 0000000..2bc0901
--- /dev/null
+++ b/com.google.eclipse.protobuf.test/src/com/google/eclipse/protobuf/bugs/MapSyntaxTest.java
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2014 Google Inc.
+ *
+ * All rights reserved. This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+package com.google.eclipse.protobuf.bugs;
+
+import static com.google.eclipse.protobuf.junit.core.UnitTestModule.unitTestModule;
+import static com.google.eclipse.protobuf.junit.core.XtextRule.overrideRuntimeModuleWith;
+import static org.junit.Assert.assertTrue;
+
+import com.google.eclipse.protobuf.junit.core.XtextRule;
+import com.google.eclipse.protobuf.validation.ProtobufJavaValidator;
+import com.google.inject.Inject;
+
+import org.eclipse.emf.common.util.BasicDiagnostic;
+import org.junit.Rule;
+import org.junit.Test;
+
+/**
+ * Test that the parser correctly handles map syntax.
+ */
+public class MapSyntaxTest {
+  @Rule public XtextRule xtext = overrideRuntimeModuleWith(unitTestModule());
+
+  @Inject private ProtobufJavaValidator validator;
+
+  // syntax = "proto2";
+  //
+  // message Foo {
+  //   optional map<string, Bar> bar_map = 1;
+  // }
+  @Test public void shouldAllowMapFields() {
+    boolean isValid = validator.validate(xtext.root(), new BasicDiagnostic(), null);
+    assertTrue(isValid);
+  }
+}

com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext

diff --git a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
index dddd42f..0ce144f 100644
--- a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
+++ b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
@@ -96,7 +96,7 @@
   optional | required | repeated;
 
 TypeLink:
-  ScalarTypeLink | ComplexTypeLink;
+  ScalarTypeLink | ComplexTypeLink | MapTypeLink;
 
 ScalarTypeLink:
   target=ScalarType;
@@ -107,6 +107,12 @@
 
 ComplexTypeLink:
   target=[ComplexType|QualifiedName];
+  
+MapTypeLink:
+  target=MapType;
+
+MapType:
+  =>'map' '<' fromType=TypeLink ',' toType=TypeLink '>';
 
 Enum:
   =>'enum' name=Name '{'