p.advance(_Operator, _Semi, _Rparen, _Rbrack, _Rbrace)
	}

	return t
}

// ParameterDecl = [ IdentifierList ] [ "..." ] Type .
func (p *parser) paramDeclOrNil(name *Name, follow token) *Field {
	if trace {
		defer p.trace("paramDeclOrNil")()
	}

	// type set notation is ok in type parameter lists
	typeSetsOk := follow == _Rbrack

	pos := p.pos()
	if name != nil {
		pos = name.pos

	name *ast.Ident
	typ  ast.Expr
}

func (p *parser) parseParamDecl(name *ast.Ident, typeSetsOK bool) (f field) {
	// TODO(rFindley) refactor to be more similar to paramDeclOrNil in the syntax
	// package
	if p.trace {
		defer un(trace(p, "ParamDeclOrNil"))
	}

	ptok := p.tok
	if name != nil {
		p.tok = token.IDENT // force token.IDENT case in switch below
	} else if typeSetsOK && p.tok == token.TILDE {