Create synthetic iterator boundaries between open and close tags

If no non-negative integer exists between an open and close tag code,
we still need to report a boundary there, since close tags always have
to come first at any given iterator position.

:pear:ed with @as-cii

spec/tokenized-buffer-iterator-spec.js

@@ -0,0 +1,40 @@
+/** @babel */
+
+import TokenizedBufferIterator from '../src/tokenized-buffer-iterator'
+import {Point} from 'text-buffer'
+
+describe('TokenizedBufferIterator', () => {
+  it('reports two boundaries at the same position when tags close, open, then close again without a non-negative integer separating them (regression)', () => {
+    const tokenizedBuffer = {
+      tokenizedLineForRow () {
+        return {
+          tags: [-1, -2, -1, -2],
+          text: '',
+          openScopes: []
+        }
+      }
+    }
+
+    const grammarRegistry = {
+      scopeForId () {
+        return 'foo'
+      }
+    }
+
+    const iterator = new TokenizedBufferIterator(tokenizedBuffer, grammarRegistry)
+
+    iterator.seek(Point(0, 0))
+    expect(iterator.getPosition()).toEqual(Point(0, 0))
+    expect(iterator.getCloseTags()).toEqual([])
+    expect(iterator.getOpenTags()).toEqual(['foo'])
+
+    iterator.moveToSuccessor()
+    expect(iterator.getPosition()).toEqual(Point(0, 0))
+    expect(iterator.getCloseTags()).toEqual(['foo'])
+    expect(iterator.getOpenTags()).toEqual(['foo'])
+
+    iterator.moveToSuccessor()
+    expect(iterator.getCloseTags()).toEqual(['foo'])
+    expect(iterator.getOpenTags()).toEqual([])
+  })
+})

src/tokenized-buffer-iterator.coffee

@@ -28,7 +28,11 @@ class TokenizedBufferIterator
       else
         scopeName = @grammarRegistry.scopeForId(tag)
         if tag % 2 is 0
-          @closeTags.push(scopeName)
+          if @openTags.length > 0
+            @tagIndex = index
+            break
+          else
+            @closeTags.push(scopeName)
         else
           @openTags.push(scopeName)
 
@@ -56,7 +60,10 @@ class TokenizedBufferIterator
         else
           scopeName = @grammarRegistry.scopeForId(tag)
           if tag % 2 is 0
-            @closeTags.push(scopeName)
+            if @openTags.length > 0
+              break
+            else
+              @closeTags.push(scopeName)
           else
             @openTags.push(scopeName)
         @tagIndex++