flag <- and prop as errors

syntax/beluga.vim

@@ -1,15 +1,15 @@
 if exists('b:current_syntax')
   finish
 endif
-let b:current_syntax = 'maude'
+let b:current_syntax = 'beluga'
 
 setlocal iskeyword=48-57,a-z,A-Z,!,$,&,',*,+,_,/,=,@,-,~,#,^
 
-syn match belArrowEtc /->\|=>\|→\|←\|⇒\||-#\?\|⊢\|\<=\>\|:/
+syn match belArrowEtc /->\|=>\|→\|⇒\||-#\?\|⊢\|\<=\>\|:/
 hi def link belArrowEtc Function
 
-syn match belBrack /[()[\]{}.;,]\|\<\/\>\||-\@!/
-hi def link belBrack Delimiter
+syn match belDelim /[()[\]{}.;,]\|\<\/\>\||-\@!\|<\|-\@<!>/
+hi def link belDelim Delimiter
 
 syn match belComment /%\s.*$/
 hi def link belComment Comment
@@ -35,12 +35,18 @@ hi def link belTotal Special
 syn keyword belTrust trust
 hi def link belTrust Underlined
 
-syn match belIdSubst /\.\./
-hi def link belIdSubst Constant
+syn match belSubstConst /\.\.\|\^/
+hi def link belSubstConst Constant
 
 syn keyword belIdBlock some block
 hi def link belIdBlock Structure
 
+syn keyword belModule module struct end
+hi def link belModule Structure
+
+syn match belQualName /\>::\</
+hi def link belQualName Normal
+
 syn match belVarVar /#\k\+/
 hi def link belVarVar Constant
 
@@ -71,3 +77,7 @@ hi def link belBool Boolean
 
 syn keyword belIf if then else
 hi def link belIf Keyword
+
+syn match belugaError /<-/
+syn keyword belugaError prop
+hi def link belugaError Error