Add regression test: #15987, SRTP overload resolution returns correct typed value

tests/FSharp.Compiler.ComponentTests/Conformance/Types/TypeConstraints/IWSAMsAndSRTPs/IWSAMsAndSRTPsTests.fs

@@ -1831,3 +1831,29 @@ let _x3 = curryN f3 1 2 3
         FSharp "module T\nopen CsLib\nlet _ = IP.Get()" |> asExe |> withOptions iwsamWarnings |> withReferences [csLib]
         |> compileAndRun |> shouldSucceed
 
+    // https://github.com/dotnet/fsharp/issues/15987
+    [<Fact>]
+    let ``Issue 15987 - SRTP overload resolution returns correct value for typed argument`` () =
+        FSharp """
+module Test
+
+type A = A with
+    static member ($) (A, a: float  ) = 0.0
+    static member ($) (A, a: decimal) = 0M
+    static member ($) (A, a: 't     ) = 0
+
+let inline call x = ($) A x
+
+// Verify correct overload is selected: float argument should use the float overload
+let resultFloat: float = call 42.0
+let resultDecimal: decimal = call 42M
+let resultInt: int = call 42
+
+if resultFloat <> 0.0 then failwith $"Expected 0.0 but got {resultFloat}"
+if resultDecimal <> 0M then failwith $"Expected 0M but got {resultDecimal}"
+if resultInt <> 0 then failwith $"Expected 0 but got {resultInt}"
+"""
+        |> asExe
+        |> compileAndRun
+        |> shouldSucceed
+