override completion doesn't insert full signature

[333fred]

Issue Description

Override completion does not insert the full signature.

Steps to Reproduce

1. Create a C# project with a class like this:

class C1
{
	public virtual void M() {}
}
class C2 : C1
{
    // Type here
}

2. At // Type here, replace the comment with override <space> <ctrl+space>. Valid override method completion should appear.
3. Select M to override.

Expected Behavior

The full signature of M is inserted, so you end up with public override void M() on the current line.

Actual Behavior

Just M() is inserted, missing the accessibility modifier and the return type.

Logs

OmniSharp log

Post the output from Output-->OmniSharp log here

C# log

Post the output from Output-->C# here

Environment information

VSCode version: 1.42.1
C# Extension: 1.21.12

Dotnet Information

.NET Core SDK (reflecting any global.json): Version: 3.1.200-preview-014977 Commit: ca5522cead

Runtime Environment:
OS Name: Windows
OS Version: 10.0.18363
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\3.1.200-preview-014977\

Host (useful for support):
Version: 3.1.1
Commit: a1388f194c

.NET Core SDKs installed:
3.0.100-preview8-013437 [C:\Program Files\dotnet\sdk]
3.1.100 [C:\Program Files\dotnet\sdk]
3.1.200-preview-014977 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.0.0-preview8.19374.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.0-preview2.19528.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.0.0-preview8-28373-17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.0-preview2.19525.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.0.0-preview8-28373-17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.0-preview2.19525.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 3.1.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download

Visual Studio Code Extensions

Extension	Author	Version
auto-close-tag	formulahendry	0.5.6
auto-rename-tag	formulahendry	0.1.1
azure-account	ms-vscode	0.8.8
azure-pipelines	ms-azure-devops	1.165.1
code-settings-sync	Shan	3.4.3
cpptools	ms-vscode	0.26.3
csharp	ms-vscode	1.21.12
dotnet-test-explorer	formulahendry	0.7.1
EditorConfig	EditorConfig	0.14.4
gitignore	codezombiech	0.6.0
gitlens	eamodio	10.2.1
language-haskell	justusadam	2.7.0
ocean-dark-extended	kleber-swf	1.5.0
path-intellisense	christian-kohler	1.4.2
powershell	ms-vscode	2020.1.0
vim	vscodevim	1.12.4
vscode-hexdump	slevesque	1.7.2
vscode-icons	vscode-icons-team	10.0.0
vscode-il	soltys	0.0.1
vsonline	ms-vsonline	1.0.1672
xml	DotJoshJohnson	2.5.0

[filipw]

This is not really a "bug" more like a "known limitation".

We will have better support for this when we move to the Roslyn completion service, I have a WIP branch for this in Omnisharp-roslyn.