[110.79] Compiler bug: Unify: unifyTy: arg ty lists wrong length

[spamegg1]

Version

Pre-110.97

Operating System

• Any
• Linux
• macOS
• Windows
• Other Unix

OS Version

Ubuntu 22.04 Jammy

Processor

• Any
• Arm (using Rosetta)
• PowerPC
• Sparc
• x86 (32-bit)
• x86-64 (64-bit)
• Other

System Component

SML/NJ Library

Severity

Minor

Description

SML/NJ version 110.79

A "Compiler bug" is reported by the REPL whenever I make an incorrect use of the type SMLofNJ.Cont.cont that does not type-check, which I then try to use with Signals.HANDLER.

If I remove the type annotation and let it be inferred, or use 'a C.Cont instead, the "Compiler bug" report does not happen.

Transcript

Standard ML of New Jersey v110.79 [built: Sat Oct 26 12:27:04 2019]
use "test.sml";
[opening test.sml]
[autoloading]
[library $SMLNJ-BASIS/basis.cm is stable]
[library $SMLNJ-BASIS/(basis.cm):basis-common.cm is stable]
[autoloading done]
test.sml:5.55-5.61 Error: type constructor Cont.cont given 0 arguments, wants 1
test.sml:5.64-5.70 Error: type constructor Cont.cont given 0 arguments, wants 1
Error: Compiler bug: Unify: unifyTy: arg ty lists wrong length

uncaught exception Error
raised at: ../compiler/Basics/errormsg/errormsg.sml:52.14-52.19
../compiler/Elaborator/types/unify.sml:310.13
../compiler/Elaborator/types/unify.sml:310.13
../compiler/Elaborator/types/unify.sml:310.13
../compiler/Elaborator/types/unify.sml:310.13
../compiler/Elaborator/types/typecheck.sml:625.12
../compiler/Basics/stats/stats.sml:198.40
../compiler/Elaborator/elaborate/elabmod.sml:1741.65
../compiler/Elaborator/elaborate/elabmod.sml:1745.59
../compiler/Basics/stats/stats.sml:198.40
../compiler/TopLevel/interact/evalloop.sml:44.55
../compiler/TopLevel/interact/evalloop.sml:292.17-292.20

Expected Behavior

Not sure.

Steps to Reproduce

I tried to minimize the code. It might be possible to minimize it further.

(* this is file test.sml *)
structure S = Signals
structure C = SMLofNJ.Cont

(*   deliberately wrong type annotation here, should be 'a C.cont *)
fun interrupt_handler(signal: S.signal, n: int, cont: C.cont): C.cont = cont

fun main(arg0: string, argv: string list): OS.Process.status = (
    S.setHandler(S.sigINT, S.HANDLER interrupt_handler);
    OS.Process.success
)

Now run it on the REPL with use "test.sml";

Additional Information

No response

Email address

spamegg@pm.me

[JohnReppy]

This issue has been fixed since 110.79 (110.99.3 works correctly), so I am going to close it.