问题
I was trying to use a fsi file to allow mutually recursive classes in separate files, but my fsi file did not compile. Below is a simple example which demonstrates the problem.
File program.fs:
module mod1
type first =
|zero = 0
File File1.fs:
module mod2
type second =
|zero2 = 0
Compiling with --sig:signature.fsi produces:
#light
module mod1
type first =
| zero = 0
module mod2
type second =
| zero2 = 0
Which has an error on the line
type second
Which is
Error 1 Unexpected keyword 'type' in signature file. Expected ':', '=' or other token.
回答1:
You'd think that this is what signature files are for (like C++ header files), but it's not. At least, that's what I thought at first.
The only way to define mutually recursive types in F# is to put them in the same source file and use the and keyword:
module mod1_mod2
type first =
| zero = 0
and second =
| zero2 = 0
来源：https://stackoverflow.com/questions/1866231/f-signature-file-error