Syntax: Don't highlight the LHS of type decl as types

I would expect 'ocamlTypeConstr' to apply only to type constructors
within type expressions, not to the identifier after 'type' in:

    type foo = 'a bar list

This makes the LHS of types, exceptions and constraints be matched as
'ocamlTypedef', which is not highlighted by default.

Variance and type variables on the LHS remain highlighted as before.

Author: Julow

syntax/ocaml.vim

@@ -465,13 +465,23 @@ syn region ocamlTypeSumAnnot contained
 \ contains=@ocamlTypeExpr,ocamlTypeRecordDecl,ocamlComment,ocamlPpx
 hi link ocamlTypeSumAnnot ocamlTypeCatchAll
 
+" RHS of a ocamlTypeDef
+syn region ocamlTypeDefImpl
+\ matchgroup=ocamlKeyword start="\(=\|:\|of\)"
+\ matchgroup=NONE end="\(\<type\>\|\<exception\>\|\<val\>\|\<module\>\|\<class\>\|\<method\>\|\<constraint\>\|\<inherit\>\|\<object\>\|\<struct\>\|\<open\>\|\<include\>\|\<let\>\|\<external\>\|\<in\>\|\<end\>\|)\|]\|}\|;\|;;\)\@="
+\ contained skipwhite skipempty
+\ contains=@ocamlTypeExpr,ocamlTypeEq,ocamlTypePrivate,ocamlTypeDefDots,ocamlTypeRecordDecl,ocamlTypeSumDecl,ocamlTypeDefAnd,ocamlComment,ocamlPpx
+hi link ocamlTypeDefImpl ocamlTypeCatchAll
+
 " Type context opened by “type” (type definition), “constraint” (type
 " constraint) and “exception” (exception definition)
 syn region ocamlTypeDef
 \ matchgroup=ocamlKeyword start="\<type\>\(\_s\+\<nonrec\>\)\?\|\<constraint\>\|\<exception\>"
-\ matchgroup=NONE end="\(\<type\>\|\<exception\>\|\<val\>\|\<module\>\|\<class\>\|\<method\>\|\<constraint\>\|\<inherit\>\|\<object\>\|\<struct\>\|\<open\>\|\<include\>\|\<let\>\|\<external\>\|\<in\>\|\<end\>\|)\|]\|}\|;\|;;\)\@="
-\ contains=@ocamlTypeExpr,ocamlTypeEq,ocamlTypePrivate,ocamlTypeDefDots,ocamlTypeRecordDecl,ocamlTypeSumDecl,ocamlTypeDefAnd,ocamlComment,ocamlPpx
-hi link ocamlTypeDef ocamlTypeCatchAll
+\ matchgroup=ocamlTypedef end="\<\(\w\|'\)*\>"
+\ contains=@ocamlAllErrs,ocamlComment,ocamlTypeVariance,ocamlTypeVar
+\ skipwhite skipempty
+\ nextgroup=ocamlTypeDefImpl
+
 syn cluster ocamlTypeContained add=ocamlTypePrivate
 syn keyword ocamlTypePrivate contained private
 hi link ocamlTypePrivate ocamlKeyword