"Find All References" doesn't show unsaved references

[mattmccutchen-microsoft]

"Find All References" doesn't seem to show references that have been added to an open file but not saved. This is inconsistent with the behavior for C#, which is to show references based on the latest available version of each file (the editor content if the file is open, otherwise the content on disk). Is this expected?

Repro steps

1. Create a new F# library and add the following code to the file, but do not save:

type A = int
type B = A

2. Right-click the first A and choose "Find All References".

Expected behavior

The reference from type B = A is shown.

Actual behavior

"No references found to 'A'".

Known workarounds

Save all files.

Related information

Nightly Visual F# Tools 15.4.1.17070403

Microsoft Visual Studio Enterprise 2017 
Version 15.2 (26430.14) Release
VisualStudio.15.Release/15.2.0+26430.14
Microsoft .NET Framework
Version 4.7.02046

[cartermp]

This is expected, unfortunately. FCS requires the files to be saved on disk.

[vasily-kirichenko]

It should work on private symbols where we use file check results, for example it should work on function arguments and local values and functions.

[mattmccutchen-microsoft]

I guess an option would be to prompt the user, "Added references in unsaved files will not be found. Do you want to save all files first?" with a "Remember my decision". Do we think that when there are unsaved files, a high enough percentage of "Find All References" requests relate to unsaved references that a prompt would be worthwhile? I hit this many times over the past few days and decided "Find All References" was unreliable and fell back to a text search, until today when I decided to investigate and file an issue.

[0101]

This has an opt-in fix available: #14033 (comment)