Confusing error message about "partially applied functor"

[JohnReppy]

Version

110.96

Operating System

• All
• Linux
• macOS
• Windows
• Other Unix

OS Version

No response

Processor

No response

Component

Core system

Severity

Cosmetic

Description of the problem

When there is a type error in a functor definition,
where the functor is then applied to produce a structure,
there is a confusing error message about the functor
application:

Error: structure A defined by partially applied functor

Transcript

- local
=   functor F() : sig val x : int end = struct val x = "abs" end
= in
=   structure A = F()
= end;
stdIn:2.11-2.63 Error: value type in structure does not match signature spec
    name: x
  spec:   int
  actual: string
stdIn:4.17-4.20 Error: structure A defined by partially applied functor

Expected Behavior

No response

Steps to Reproduce

local
functor F() : sig val x : int end = struct val x = "abs" end
in
structure A = F()
end;

Additional Information

No response

Email address

jhr@cs.uchicago.edu

Comments from smlnj-gforge

Original smlnj-gforge bug number 246

Submitted via web form by John Reppy jhr@cs.uchicago.edu on 2020-37-31 at 17:3700

Keywords: modules

comment by @dmacqueen on 2020-55-25 00:5500 +000 UTC

The problem is that the check for a partially applied functor in a structure declaration (around line 1254 in elabmod.sml) is inaccurate when the functor declaration produces an error. A proper fix will require a somewhat delicate propagation of ERROR values (ERRORstr and ERRORfct) during module elaboration. The propagation needs to be more thorough, but not so aggressive that type checking is left out in other parts of the structures with bogus components.