On 24/01/18 08:43, Jacques Garrigue wrote:

I.e., types can be used to optimize a program, but they do not change its semantics.
It’s true of so-called “overloaded” record labels, it’s true of a labeled and default arguments
(which use type information for compilation, but not semantics), it’s true of objects,
  it’s true of GADT pattern-matching (again optimized), etc…

type foo = { x : int }
type bar = { x : string }

let f r = r.x           (* OK: uses bar *)
let f r = (r:foo).x  (* OK: uses foo *)
let f r = (r.x : int) (* type error - wrong type inferred *)


Aren't the semantics different? 'f' has different types in the first two definitions, And why does type inference fail for the last example?

Toby

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