Closures

[ryanwilsond]

Description

Previously, closure analysis was done purely to rewrite local functions into methods. This approach worked because the Evaluator keeps a stack of locals so even though the locals weren't explicitly passed to the rewritten local, it could still access them.

Now closure analysis actually creates a closure, allowing local functions to emit correctly to IL.

Source:

public static class Program {
    public static void Main() {
        var a = 3;

        Console.PrintLine(F(5));

        int F(int b) {
            return a + b;
        }
    }
}

Old (incorrect):

public static Nullable<int> Program.<Main>ss__F|0_0(Nullable<int> b) {
    return ((a.get_HasValue() && b.get_HasValue()) ? new Nullable<int>((a.get_Value() + b.get_Value())) : null)
}

public static void Program.Main() {
    Nullable<int> a = new Nullable<int>(3)
    Nullable<int> temp0 = Program!.<Main>ss__F|0_0(5)
    global::Console.PrintLine((temp0.get_HasValue() ? (string!)temp0.get_Value() : null))
    nop
    return
}

New (correct):

public Nullable<int> Program.<>Closure__0.<Main>g__F|1_1(Nullable<int> b) {
    return ((this.a.get_HasValue() && b.get_HasValue()) ? new Nullable<int>((this.a.get_Value() + b.get_Value())) : null)
}

public void Program.<>Closure__0..ctor() {
    this..ctor()
    return
}

public static void Program.Main() {
    private sealed Program.<>Closure__0 <>Closure__0_l0 = new Program.<>Closure__0()
    <>Closure__0_l0.a = new Nullable<int>(3)
    Nullable<int> temp0 = <>Closure__0_l0.<Main>g__F|1_1(5)
    global::Console.PrintLine((temp0.get_HasValue() ? (string!)temp0.get_Value() : null))
    nop
    return
}