Missing type recovery

[trefis]

Type recovery at the level of structure items is lackluster: mostly it just drops the item if an error happens at the level of the item, which is painful for blocks of recursive definitions.

For instance:

let rec foo x = x + a + b
and (a,b) = (1,2)

The whole block is dropped.

The are a couple of similar errors in that area, which could be gracefully recovered from. But mostly I think recursive blocks should get special treatment where each definition gets recovered/dropped separately from the others.