Internal error, LocallyAbortOperationThatFailsToResolveOverload with SRTP #7217
Description
With certain SRTP constructions the compiler produces an FSharp.Compiler.ConstraintSolver+LocallyAbortOperationThatFailsToResolveOverload
internal error.
Repro steps
The naming in the snippet was modified to obfuscate the real logic as this was an experiment for a customer.
module TargetA =
[<RequireQualifiedAccess>]
type TransformerKind =
| A
| B
type M1 = int
type M2 = float
type Target() =
member __.TransformM1 (kind: TransformerKind) : M1[] option = [| 0 |] |> Some
member __.TransformM2 (kind: TransformerKind) : M2[] option = [| 1. |] |> Some
type TargetA =
static member instance : Target option = None
static member inline Transform(_: ^r, _: TargetA) = fun (kind:TransformerKind) -> TargetA.instance.Value.TransformM1 kind : ^r
static member inline Transform(_: ^r, _: TargetA) = fun (kind:TransformerKind) -> TargetA.instance.Value.TransformM2 kind : ^r
static member inline Transform(kind: TransformerKind) =
let inline call2(a:^a, b:^b) = ((^a or ^b) : (static member Transform: _ * _ -> _) b, a)
let inline call (a: 'a) = fun (x: 'x) -> call2(a, Unchecked.defaultof<'r>) x : 'r
call Unchecked.defaultof<TargetA> kind
let inline Transform kind = TargetA.Transform kind
module TargetB =
[<RequireQualifiedAccess>]
type TransformerKind =
| C
| D
type M1 = | M1
type M2 = | M2
type Target() =
member __.TransformM1 (kind: TransformerKind) = [| M1 |] |> Some
member __.TransformM2 (kind: TransformerKind) = [| M2 |] |> Some
type TargetB =
static member instance : Target option = None
static member inline Transform(_: ^r, _: TargetB) = fun (kind:TransformerKind) -> TargetB.instance.Value.TransformM1 kind : ^r
static member inline Transform(_: ^r, _: TargetB) = fun (kind:TransformerKind) -> TargetB.instance.Value.TransformM2 kind : ^r
static member inline Transform(kind: TransformerKind) =
let inline call2(a:^a, b:^b) = ((^a or ^b) : (static member Transform: _ * _ -> _) b, a)
let inline call (a: 'a) = fun (x: 'x) -> call2(a, Unchecked.defaultof<'r>) x : 'r
call Unchecked.defaultof<TargetB> kind
let inline Transform kind = TargetB.Transform kind
module Superpower =
type Transformer =
static member inline Transform(_: ^f, _: TargetB.TargetB, _: Transformer) = fun x -> TargetB.Transform x : ^f
static member inline Transform(_: ^r, _: TargetA.TargetA, _: Transformer) = fun x -> TargetA.Transform x : ^r
static member inline YeahTransform kind =
let inline call2(a:^a, b:^b, c: ^c) = ((^a or ^b or ^c) : (static member Transform: _ * _ * _ -> _) c, b, a)
let inline call (a: 'a) = fun (x: 'x) -> call2(a, Unchecked.defaultof<_>, Unchecked.defaultof<'r>) x : 'r
call Unchecked.defaultof<Transformer> kind
module Examples =
let a kind = Superpower.Transformer.YeahTransform kind : TargetA.M1[]
let b = Superpower.Transformer.YeahTransform TargetA.TransformerKind.A : TargetA.M2[] option
let c = Superpower.Transformer.YeahTransform TargetB.TransformerKind.C : TargetB.M1[] option
let d = Superpower.Transformer.YeahTransform TargetA.TransformerKind.A : TargetA.M1[] optionExpected behavior
Compiler shows possible overloads error.
Actual behavior
Compiler fails with an internal error message:
Type constraint mismatch when applying the default type 'obj' for a type inference variable. internal error: Exception of type 'FSharp.Compiler.ConstraintSolver+LocallyAbortOperationThatFailsToResolveOverload' was thrown. Consider adding further type constraintsF# Compiler(71)
Known workarounds
Just know what you're doing and use the correct overloads or just don't use SRTP's in such a bad manner 😂
Related information
Provide any related information (optional):
.NET Core SDK (gemäß "global.json"):
Version: 2.2.300
Commit: 73efd5bd87
Laufzeitumgebung:
OS Name: ubuntu
OS Version: 18.10
OS Platform: Linux
RID: ubuntu.18.10-x64
Base Path: /usr/share/dotnet/sdk/2.2.300/
Host (useful for support):
Version: 2.2.5
Commit: 0a3c9209c0
.NET Core SDKs installed:
2.2.300 [/usr/share/dotnet/sdk]
.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.2.5 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.2.5 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.2.5 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download