FSharp.Compiler.SyntaxTreeX is a subtree of FSharp.Compiler.SyntaxTree. You can use it to determine whether two pieces of code are equal. FSharp.Compiler.SyntaxTreeX removes the xmldoc and range information from FSharp.Compiler.SyntaxTree.

when anonymous module:

let decls:XModuleDecl list = 
    Parser.getDecls("header.fsx",text)

when named module:

let decls:XModuleDecl list = 
    Parser.getDecls("header.fs",text)