Fix inline link reference and definition

spec/features/inline_links.md

@@ -39,6 +39,7 @@ Link with newline between URL and title it's ok [link](http://example.com
 
 # This is [link](http://github.com) in a title
 
+[Link](http://example.com) at beginning of the line. Bug: this was considered as link definition
 
 
 ---

spec/features/inline_links.md.html

@@ -70,6 +70,7 @@
 
 <span class="Special">#</span><span class="Title"> This is </span><span class="Special">[</span><span class="Underlined">link</span><span class="Special">]</span><span class="Special">(</span><span class="Underlined"><a href="http://github.com">http://github.com</a></span><span class="Special">)</span><span class="Title"> in a title</span>
 
+<span class="Special">[</span><span class="Underlined">Link</span><span class="Special">]</span><span class="Special">(</span><span class="Underlined"><a href="http://example.com">http://example.com</a></span><span class="Special">)</span> at beginning of the line. Bug: this was considered as link definition
 
 
 <span class="Identifier">---</span>

spec/features/inline_references.md

@@ -36,6 +36,9 @@ breaks][]
 
 [line breaks]: http://example.com "Yes this works"
 
+---
+The following should be supported but they are not... In GFM and Kramdown link references could omit the second pair of square brackets, with a programming language is possible to check if something between square brackets has a related link definition an so to be interpreted as link reference but here it would be impossible
+
 [short ref]
 
 [short

spec/features/inline_references.md.html

@@ -16,6 +16,7 @@
 .NonText { color: #8080ff; }
 .Underlined { color: #c000c0; text-decoration: underline; }
 .Special { color: #c000c0; }
+.Identifier { color: #008080; }
 -->
 </style>
 
@@ -65,14 +66,17 @@
 
 <span class="NonText">[line breaks]: <a href="http://example.com">http://example.com</a> &quot;Yes this works&quot;</span>
 
-<span class="NonText">[short ref]</span>
+<span class="Identifier">---</span>
+The following should be supported but they are not... In GFM and Kramdown link references could omit the second pair of square brackets, with a programming language is possible to check if something between square brackets has a related link definition an so to be interpreted as link reference but here it would be impossible
 
-<span class="NonText">[short</span>
-<span class="NonText">ref]</span>
+[short ref]
+
+[short
+ref]
 
 <span class="NonText">[short ref]: <a href="http://example.com">http://example.com</a> &quot;No more hanging empty bracket!&quot;</span>
 
-<span class="NonText">[a ref]</span>
+[a ref]
 
 <span class="NonText">[a ref]: <a href="http://example.com">http://example.com</a></span>
 <span class="NonText">    &quot;Title on next line.&quot;</span>

syntax/markdown.vim

@@ -278,10 +278,8 @@ execute 'syn match markdownLinkReference '
   \ . '/'
   \ . '^\s\{,3}'
   \ . b:markdown_syntax_square_brackets_block
-  \ . '\%('
-  \ .   ':.*'
-  \ .   '\%(\n\%\(\n\)\@!.*$\)\?'
-  \ . '\)\?'
+  \ . ':.*'
+  \ . '\%(\n\%\(\n\)\@!.*$\)*'
   \ . '/'
 
 syn region markdownBlockquote start=/^\s*\%(>\s\?\)\+\%(.\)\@=/ end=/\n\n/ contains=markdownBlockquoteDelimiter,@NoSpell