Saving cells

As an assembly

.save writes the current cell as a real assembly with a static IlRepl.Cell.Run method. The cell is kept, so you can still run it.

il[1]> .args (int32 n = 0)
il[1]> ldarg n
il[1]> ldc.i4 2
il[1]> mul
il[1]> .save doubler.dll
  wrote /home/you/doubler.dll with IlRepl.Cell.Run

The file loads like any other assembly:

var assembly = Assembly.LoadFrom("doubler.dll");
var run = assembly.GetType("IlRepl.Cell")!.GetMethod("Run")!;
Console.WriteLine(run.Invoke(null, [21])); // 42

Saving uses PersistedAssemblyBuilder, so the output has real metadata: declared parameters, locals, exception blocks, and tokens for every member the cell references.

As ILAsm

.il renders the cell as ILAsm source and .save with an .il extension is not needed because you can copy it from the transcript. Operands are fully qualified so the text assembles with ilasm after adding the assembly references it lists.

il[2]> .il
.assembly extern System.Runtime {}
.assembly ilrepl_cell {}
.module ilrepl_cell.dll

.class public abstract sealed auto ansi beforefieldinit IlRepl.Cell extends [System.Runtime]System.Object
{
    .method public static object Run(int32 n) cil managed
    {
        .maxstack 16
        ldarg n
        ldc.i4 2
        mul
        box int32
        ret
    }
}