Get syntax highlighting on code blocks working again.

compiler/Generate/Markdown.hs

@@ -1,6 +1,39 @@
 module Generate.Markdown where
 
 import Text.Pandoc
+import qualified Data.Set as Set
 
 toHtml :: String -> String
-toHtml = writeHtmlString def . readMarkdown def
+toHtml = writeHtmlString writeOptions . readMarkdown readOptions
+
+readOptions =
+    def { readerExtensions  = elmExtensions
+        , readerApplyMacros = False
+        }
+
+writeOptions =
+    def { writerExtensions = elmExtensions
+        , writerHighlight = True
+        }
+
+elmExtensions :: Set.Set Extension
+elmExtensions = Set.fromList
+  [ Ext_raw_html
+  , Ext_fenced_code_blocks
+  , Ext_fenced_code_attributes
+  , Ext_backtick_code_blocks
+  , Ext_inline_code_attributes
+  , Ext_markdown_in_html_blocks
+  , Ext_escaped_line_breaks
+  , Ext_fancy_lists
+  , Ext_startnum
+  , Ext_definition_lists
+  , Ext_example_lists
+  , Ext_all_symbols_escapable
+  , Ext_intraword_underscores
+  , Ext_blank_before_blockquote
+  , Ext_blank_before_header
+  , Ext_auto_identifiers
+  , Ext_header_attributes
+  , Ext_implicit_header_references
+  ]