Visual F# Tools leak memory while reloading solutions

[KevinRansom]

Scenario:
◾Disable VFPT in VS if it is installed
◾Open VFPT solution (https://github.com/fsprojects/VisualFSharpPowerTools), VS occupies ~ 300MB RAM
◾Repeat the following steps 15 times: (1) Switch to a new git branch (2) Reload the solution (3) Rebuild the solution
◾VS now occupies ~ 1.7 GB RAM

Context:
We are hunting down memory leaks in Visual F# Power Tools. It turned out FSharp.Compiler.Service (FCS) leaked memories when Xaml type providers (FsXaml) didn't dispose resources correctly. These bugs have been fixed in FCS and FsXaml. See the discussion at fsharp/fsharp-compiler-docs#158.

After bug fixing, there are still memory leaks. I think Visual F# Tools has the same issue where type providers are in use. We did profile using PerfView without enabling VFPT. Here is a diff of two snapshots where we reload and rebuild solutions twice.

https://cloud.githubusercontent.com/assets/941060/3277997/c56876ec-f39f-11e3-8042-4840c6cffffd.png

https://cloud.githubusercontent.com/assets/941060/3278000/13a16d6e-f3a0-11e3-97cd-b994b8086d8e.png

Configuration:

• Visual Studio 2013
• Windows 7
• A recent build of Visual F# Tools 3.1.1

I believe the fix should be similar to that of FCS. Here are relevant commits:
fsharp/fsharp-compiler-docs@a325df2
fsharp/fsharp-compiler-docs@4e7c8bc

Let me know if you need more information.

[dsyme]

We should apply the linked fix to VF# Tools.

[forki]

/cc @quasilord

[forki]

We should apply the linked fix to VF# Tools.

I tried to do this, but there are more commits involved.

[latkin]

This was partially addressed by recent fix from @dsyme, but it looks like we still leak a bunch on reload. I've left it open to keep tracking remaining leaks.

Moving out of VS 2015 milestone, though.

[dsyme]

@latkin AFAIK a well written type provider shouldn't leak on reload. What repro steps should I follow to check this out (I'm ok with this being vNext)