[Haskell-cafe] Adding type annotations to an AST?

[Stephen Tetley]

Hello All

How do I add type annotations to interior locations in an abstract syntax tree?

I have a small ML language where programs are a single expression, but
the expression type has let-rec so it supports recursive function
definitions. Source programs have no type annotations.

I want to annotate the lec-rec with type annotations, but my type
inference is a simple implementation of Algorithm J so it seems
"monolithic" to me - i.e. the type it infers is the type of the whole
program, I would also like  the types of any internal let-rec
definitions so I can label my AST.

What is the idiom for accomplishing this?

I'm using Eijiro Sumii's MinCaml as reference - this embeds mutable
references for types in the AST. So this appears a non-starter.

My other thought is to uniquely label all type locations during
parsing then collect them in a map (location -> type) whilst computing
the outermost type - I presume I can identify inner types as they are
resolved during Algorithm J's run...

Any solutions?

Many thanks

Stephen