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AttachMembers doesn't work with operators #2825
Description
Description
Incorrect function name is used at operator call site.
Repro code
open Fable.Core
[<AttachMembers>]
type Number =
| Float of float
| Int of int
static member (+)(n1: Number, n2: Number) =
match (n1, n2) with
| (Float f1, Float f2) -> Float(f1 + f2)
| (Float f, Int i) -> Float(f + float i)
| (Int i, Float f) -> Float(float i + f)
| (Int i1, Int i2) -> Int(i1 + i2)
Int 2 + Float 2 |> printfn "%O"Expected
Number$.op_Addition(new Number$(1, 2), new Number$(0, 2))
Actual
Number$["+"](new Number$(1, 2), new Number$(0, 2))
export class Number$ extends Union {
constructor(tag, ...fields) {
super();
this.tag = (tag | 0);
this.fields = fields;
}
cases() {
return ["Float", "Int"];
}
static op_Addition(n1, n2) {
let i1, i2, f_1, i_1, f, i, f1, f2;
const matchValue = [n1, n2];
return (matchValue[0].tag === 1) ? ((matchValue[1].tag === 1) ? ((i1 = (matchValue[0].fields[0] | 0), (i2 = (matchValue[1].fields[0] | 0), new Number$(1, i1 + i2)))) : ((f_1 = matchValue[1].fields[0], (i_1 = (matchValue[0].fields[0] | 0), new Number$(0, i_1 + f_1))))) : ((matchValue[1].tag === 1) ? ((f = matchValue[0].fields[0], (i = (matchValue[1].fields[0] | 0), new Number$(0, f + i)))) : ((f1 = matchValue[0].fields[0], (f2 = matchValue[1].fields[0], new Number$(0, f1 + f2)))));
}
}
(function () {
const arg10 = Number$["+"](new Number$(1, 2), new Number$(0, 2));
toConsole(printf("%O"))(arg10);
})();Related information
- REPL: 3.7.0
- Fable: 3.7.0-beta-015
Activity
github-actions commentedon Apr 21, 2026
🤖 This is an automated response from Repo Assist.
This issue was filed against Fable 3.7.0-beta. Based on a code review of the current Fable 4.x source, this bug appears to have been fixed.
Root cause (3.7.0-beta): The call path for a static operator on an
[<AttachMembers>]type usedgetMemberDisplayName(memb)to look up the member name, which returns the F# operator symbol"+"forop_Addition. This caused the wrong property accessNumber$["+"]to be generated at the call site, while the declaration correctly usedop_Addition.Current behaviour (4.x):
getAbstractMemberInfoinFSharp2Fable.Util.fsnow usesmemb.CompiledName(which returns"op_Addition") for non-getter/setter attached members. Both the declaration path (transformExplicitlyAttachedMemberviaFsMemberFunctionOrValue.CompiledName(memb)) and the call path now agree on"op_Addition", so the generated code uses the correct identifier.If you're still seeing this with a current Fable release, please reopen and share a minimal repro. Otherwise, feel free to close this issue.