anchor.diff:                    decls, (openOk, moduleAbbrevOk, attrs)
   
                 | SynModuleDecl.Exception (SynExceptionDefn(repr,members,_),_m) -> 
  -                  if not openOk then errorR(Error(FSComp.SR.tcOpenFirstInMutRec(),m))
                     let (SynExceptionDefnRepr(synAttrs,UnionCase(_,id,_args,_,_,_),_repr,doc,vis,m)) = repr
                     let compInfo = ComponentInfo(synAttrs,[],[],[id],doc,false,vis,id.idRange)
                     let decls = [ MutRecShape.Tycon(SynTypeDefn.TypeDefn(compInfo, SynTypeDefnRepr.Exception repr, members, m)) ]
  
positive.code:                     error(Error(FSComp.SR.tcUnsupportedMutRecDecl(),def.Range)))
  
                |> fst
            loop defs
          return TcDeclarations.TcMutRecSignatureDecls cenv envInitial parent emptyUnscopedTyparEnv (mutRecDefns,m,scopem)
      }
  
  
negative.code:                       let decls = [ MutRecShape.Open (MutRecDataForOpen(lid, m)) ]
                        decls, (openOk, moduleAbbrevOk)
  
                  | SynModuleSigDecl.Exception (SynExceptionSig(exnRepr,members,_),_) ->
                        let ( SynExceptionDefnRepr(synAttrs,UnionCase(_,id,_args,_,_,_),_,doc,vis,m)) = exnRepr
                        let compInfo = ComponentInfo(synAttrs,[],[],[id],doc,false,vis,id.idRange)
                        let decls = [ MutRecShape.Tycon(SynTypeDefnSig.TypeDefnSig(compInfo, SynTypeDefnSigRepr.Exception exnRepr, members, m)) ]
                        decls, (false, false)
  
                  | SynModuleSigDecl.Val (vspec,_) -> 
                      if isNamespace then error(NumberedError(FSComp.SR.tcNamespaceCannotContainValues(),vspec.RangeOfId)) 
                      let decls = [ MutRecShape.Lets(vspec) ]
                      decls, (false, false)
  
                  | SynModuleSigDecl.NestedModule(compInfo,isRec,synDefs,_) ->
                        if isRec then warning(Error(FSComp.SR.tcRecImplied(),compInfo.Range))
                        let mutRecDefs = loop false synDefs 
                        let decls = [MutRecShape.Module (compInfo, mutRecDefs)]
                        decls, (false, false)
  
  