EnC calculates line deltas incorrectly

[tmat]

Version Used:
Version 16.10.0 Preview 3.0 [31303.14.main]

Steps to Reproduce:

Change

class C
{
    static int X() => 1;

    static int Y() => 1;
}

to

class C
{

    static int X() => 1;
    static int Y() => 1;
                            ////
}

Sequence point updates is a list of (oldLine, newLine), ordered by oldLine.
Each entry in the list applies the delta to the oldLine and all lines greater than oldLine that are less then next entry's oldLine.
Roslyn sees that X moved by one line so it produces line delta +1 for the start line of X. but then it does not compensate for Y not moving. It would need to add line delta 0 to the last line of X + 1

It might be better to change the debugger interface to accept list of (oldStartLine, oldEndLine, delta). this would mean that delta is applied on all lines in range [oldStartLine, oldEndLine). For now we can update Roslyn to produce equivalent: (oldStartLine, oldStartLine + delta), (oldEndLine, oldEndLine) - the second entry resets the delta and would only be present if there is no other delta available for that line.

Another issue is with overlapping lines:

Start with

class Program
{
    static void Main()
    {
        var p = new Program();
        var x = p.P;
        p.P = 1;
    }

    static int F() => 1;

    int P { get => F(); set => F(); }
}

and change it to:

class Program
{
    static void Main()
    {
        var p = new Program();
        var x = p.P;
        p.P = 1;
    }

    static int F() => 1;

    int P { get => 
                   F(); set => 
                               F(); }
}

Step thru the getter/setter - the debugger mapped both getter and setter to the setter.