Add test for using case statement inside if statement.

[kant2002]

No description provided.

[kant2002]

This test generates following output

public static int main()
{
	int result = 41;
	int num = 3;
	int num2 = 0;
	int num3 = num;
	if (num3 != 3)
	{
		if (num3 == 2)
		{
			goto IL_0033;
		}
	}
	else if (num2 != 0)
	{
		goto IL_0033;
	}
	goto IL_0042;
	IL_0074:
	int num4 = num4 + 1;
	goto IL_0083;
	IL_0083:
	return result;
	IL_0033:
	num4++;
	goto IL_0042;
	IL_0042:
	num = 2;
	int num5 = num;
	if (num5 != 3)
	{
		if (num5 == 2)
		{
			goto IL_0074;
		}
	}
	else if (num2 != 0)
	{
		goto IL_0074;
	}
	goto IL_0083;
}

Notice num4/num5 variables which are generated

[kant2002]

Based on diagnostics, lowering and graph transformation seems to be preserve code semantics. I'ts emit phase probably which is broken.

This is sample of code which we are sending to Emitter

{
        <var #0> = 41;
        <var #1> = 3;
        <var #2> = 0;
        <var #3> = <var #1>;
        if (<var #3>==3)
            goto d7153162-ef15-4703-9b2c-a7204926f591;
        if (<var #3>==2)
            goto 6b1382d5-216b-4d48-9efc-22c3a313745b;
        goto 711ab9d6-338e-4892-994e-79e63981d7a1;
    d7153162-ef15-4703-9b2c-a7204926f591:
            if (<var #2>)
            {
                6b1382d5-216b-4d48-9efc-22c3a313745b:
                        <var #0> = <var #0>+1;
        goto 711ab9d6-338e-4892-994e-79e63981d7a1;
    711ab9d6-338e-4892-994e-79e63981d7a1:
            ;
        <var #1> = 2;
        <var #4> = <var #1>;
        if (<var #4>==3)
            goto ee94a688-c8c0-4215-9325-4b8f59372909;
        if (<var #4>==2)
            goto 9bbb36fe-298c-46f0-8f76-d2e21f158406;
        goto abd502db-230b-4cd3-904a-f3033f978278;
    ee94a688-c8c0-4215-9325-4b8f59372909:
            if (<var #2>)
            {
                9bbb36fe-298c-46f0-8f76-d2e21f158406:
                        <var #0> = <var #0>+1;
        goto abd502db-230b-4cd3-904a-f3033f978278;
    abd502db-230b-4cd3-904a-f3033f978278:
            ;
    return <var #0>;

[kant2002]

Probably we have issues somewhere in the Linearization phase. After it, all EmitScope should be empty. When I set assert, it fails only in new test. If PR sits for too long probably good to merge and create issue asking to add

Debug.Assert(s.EmitScope == null || s.EmitScope == scope, "EmitScope should be function scope after Lineralize");

in the BlockItemEmitting.EmitCode