Parser: add recovery for missing fields after 'of' in union case

[auduchinok]

Fixes parsing and subsequent analysis for unfinished union cases and exceptions like

type U =
    | A of

exception E of

Before:

After:

[auduchinok]

There's some tests failure, but tests got broken again, so I can't debug it: #10719

[cartermp]

FCS tests pass, this one is an annoying timeout based one that seems to fail from time to time:

FSharp.Core.UnitTests.Control.AsyncModule.AwaitWaitHandle.Timeout

So restarting the PR or pushing a new change will probably have it resolve.

fsharpqa test failure looks like it's just a bad expectation, changing this:

fsharp/tests/fsharpqa/Source/Conformance/BasicTypeAndModuleDefinitions/UnionTypes/W_UnionCaseProduction01.fsx

Line 7 in d76f5ac

//<Expects id="FS0042" span="(10,12-11,1)" status="warning">This construct is deprecated: it is only for use in the F# library</Expects>

to this:

-  span="(10,12-11,1)"
+  span="(10,12-12,24)"

should fix it I think. The fsharpqa logs at least show that this was the range reported with your PR, which looks more accurate.

[cartermp]

grr, that should have done it. This is the failure log from CI:

+++ Conformance\BasicTypeAndModuleDefinitions\UnionTypes (W_UnionCaseProduction01.fsx) +++
--------------------------------------------------------
Results from hosted compiler
msg: Compiling
cmd: fsc   -a --test:ErrorRanges W_UnionCaseProduction01.fsx 
Exit code: 0
Error:     1
Microsoft (R) F# Compiler version 11.0.0.0 for F# 5.0
Copyright (c) Microsoft Corporation. All Rights Reserved.
(10,12-10,24): warning FS0042: This construct is deprecated: it is only for use in the F# library
(10,12-10,24): warning FS0042: This construct is deprecated: it is only for use in the F# library
--------------------------------------------------------
Microsoft (R) F# Compiler version 11.0.0.0 for F# 5.0
Copyright (c) Microsoft Corporation. All Rights Reserved.
(10,12-10,24): warning FS0042: This construct is deprecated: it is only for use in the F# library
(10,12-10,24): warning FS0042: This construct is deprecated: it is only for use in the F# library

*** The following necessary lines were never matched:
***	\(10,12-12,24\):.+warning FS0042:.+This construct is deprecated: it is only for use in the F# library


*** The following necessary lines were incorrectly matched:

Unexpected Compiler Output 
FAIL

Does that imply that the warning was given twice or something? I don't know how to read this (cc @KevinRansom @dsyme)

[auduchinok]

OK, let's see if it helps (though, it's not expected indeed).

[cartermp]

this should be the one that actually does it if I'm reading the log correctly.

Although it's strange that we would get two diagnostics.