No error from IntelliSense when assigning void expression to var-type local variable

[BenDeegan1001]

Type: Bug

Issue Description

If C# code includes a simultaneous declaration and assignment of a local variable of type var, where the expression to assign is of type void (e.g. Console.Writeline()), there is no error message from C# IntelliSense.
If the variable name is hovered over, a popup appears with the text "(local variable) void ". However, this does not compile, since variables may not be of type void.

Steps to Reproduce

1. Create a C# source file.
2. Enter a local variable declaration-and-assignment statement where the local variable is of type var and the expression to assign is a method returning void, e.g. "var t = Console.WriteLine();"

Expected Behavior

Red underlining of the statement from IntelliSense, and popup on hover along the lines of "error CS0815: Cannot assign void to an implicitly-typed variable", along with an "unused variable" style suggestion.

Actual Behavior

No red error message from IntelliSense, and popup on hover of "(local variable) void t", along with the expected style suggestion about an unused variable.

Extension version: 2.130.5
VS Code version: Code 1.118.1 (034f571df509819cc10b0c8129f66ef77a542f0e, 2026-04-29T17:36:44+03:00)
OS version: Windows_NT x64 10.0.26200
Modes:

Logs

C# log

Details

2026-05-02 15:52:17.156 [info] Locating .NET runtime version 10.0.5
2026-05-02 15:52:17.211 [info] Dotnet path: C:\Program Files\dotnet\dotnet.exe
2026-05-02 15:52:17.211 [info] Activating C# standalone...
2026-05-02 15:52:17.734 [info] info: Program[0]
2026-05-02 15:52:17.734 [info]       Server started with process ID 31384
2026-05-02 15:52:20.348 [info] [Program] Language server initialized
2026-05-02 15:52:20.351 [info] [Program] Monitoring client process 30936 for exit
2026-05-02 15:52:21.467 [info] [textDocument/diagnostic] [Microsoft.CodeAnalysis.MSBuild.BuildHostProcessManager] .NET BuildHost started from c:\Users\Jennifer Deegan\.vscode\extensions\ms-dotnettools.csharp-2.130.5-win32-x64\.roslyn\Microsoft.CodeAnalysis.LanguageServer.exe reloading to start from C:\Program Files\dotnet\dotnet.exe to match necessary SDK location.
2026-05-02 15:52:22.642 [warning] [textDocument/diagnostic] [LanguageServerProjectLoader] Project C:\Users\Jennifer Deegan\AppData\Local\Temp\roslyn-canonical-misc\6b29be63-ba78-4e83-8866-6458010de4aa\Canonical.csproj has unresolved dependencies
2026-05-02 15:52:22.759 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Successfully completed load of C:\Users\Jennifer Deegan\AppData\Local\Temp\roslyn-canonical-misc\6b29be63-ba78-4e83-8866-6458010de4aa\Canonical.cs
2026-05-02 15:52:22.764 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restoring Canonical.cs: Running dotnet restore on C:\Users\Jennifer Deegan\AppData\Local\Temp\roslyn-canonical-misc\6b29be63-ba78-4e83-8866-6458010de4aa\Canonical.cs
2026-05-02 15:52:22.765 [info] [textDocument/diagnostic] [Microsoft.CodeAnalysis.LanguageServer.DotnetCliHelper] Using dotnet executable configured on the PATH
2026-05-02 15:52:23.493 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restoring Canonical.cs:   Determining projects to restore...
2026-05-02 15:52:24.057 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restoring Canonical.cs:   Restored C:\Users\Jennifer Deegan\AppData\Local\Temp\roslyn-canonical-misc\6b29be63-ba78-4e83-8866-6458010de4aa\Canonical.csproj (in 267 ms).
2026-05-02 15:52:24.102 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Restore complete
2026-05-02 15:52:24.102 [info] [textDocument/diagnostic] [LanguageServerProjectLoader] Completed (re)load of all projects in 00:00:02.9184613

C# LSP Trace Logs log

Details

Environment Information

VSCode version: 1.118.1
C# Extension: 2.130.5
Using OmniSharp: false

Dotnet Information

.NET SDK: Version: 10.0.203 Commit: c23858a6d8 Workload version: 10.0.200-manifests.ef86bccd MSBuild version: 18.3.3+c23858a6d

Runtime Environment:
OS Name: Windows
OS Version: 10.0.26200
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\10.0.203\

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
Version: 10.0.7
Architecture: x64
Commit: b16286c228

.NET SDKs installed:
9.0.313 [C:\Program Files\dotnet\sdk]
10.0.203 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.26 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.26 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 10.0.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
DOTNET_CLI_UI_LANGUAGE [en-US]

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

Visual Studio Code Extensions

Extension	Author	Version	Folder Name
black-formatter	ms-python	2026.4.0	ms-python.black-formatter-2026.4.0
cmake	twxs	0.0.17	twxs.cmake-0.0.17
cmake-tools	ms-vscode	1.23.52	ms-vscode.cmake-tools-1.23.52
cpp-devtools	ms-vscode	0.5.13	ms-vscode.cpp-devtools-0.5.13
cpptools	ms-vscode	1.32.2	ms-vscode.cpptools-1.32.2-win32-x64
cpptools-extension-pack	ms-vscode	1.5.1	ms-vscode.cpptools-extension-pack-1.5.1
cpptools-themes	ms-vscode	2.0.0	ms-vscode.cpptools-themes-2.0.0
csharp	ms-dotnettools	2.130.5	ms-dotnettools.csharp-2.130.5-win32-x64
debugpy	ms-python	2026.6.0	ms-python.debugpy-2026.6.0-win32-x64
intellicode-api-usage-examples	VisualStudioExptTeam	0.2.9	visualstudioexptteam.intellicode-api-usage-examples-0.2.9
java	redhat	1.54.0	redhat.java-1.54.0-win32-x64
python	ms-python	2026.4.0	ms-python.python-2026.4.0-win32-x64
vscode-antlr4	mike-lischke	2.4.7	mike-lischke.vscode-antlr4-2.4.7
vscode-dotnet-runtime	ms-dotnettools	3.0.0	ms-dotnettools.vscode-dotnet-runtime-3.0.0
vscode-gradle	vscjava	3.17.3	vscjava.vscode-gradle-3.17.3
vscode-java-debug	vscjava	0.59.0	vscjava.vscode-java-debug-0.59.0
vscode-java-dependency	vscjava	0.27.2	vscjava.vscode-java-dependency-0.27.2
vscode-java-pack	vscjava	0.30.5	vscjava.vscode-java-pack-0.30.5
vscode-java-test	vscjava	0.45.0	vscjava.vscode-java-test-0.45.0
vscode-maven	vscjava	0.45.3	vscjava.vscode-maven-0.45.3
vscode-pylance	ms-python	2026.2.1	ms-python.vscode-pylance-2026.2.1
vscode-python-envs	ms-python	1.28.0	ms-python.vscode-python-envs-1.28.0-win32-x64
vscode-speech	ms-vscode	0.16.0	ms-vscode.vscode-speech-0.16.0-win32-x64
vscodeintellicode	VisualStudioExptTeam	1.3.2	visualstudioexptteam.vscodeintellicode-1.3.2

C# Settings

Setting	Value
preferCSharpExtension	false
compilerDiagnosticScope	openFiles
analyzerDiagnosticScope	openFiles
enableXamlTools	true
useServerGC	true

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz (12 x 3192)
GPU Status	2d_canvas: enabled GPU0: VENDOR= 0x10de, DEVICE=0x1f02 [NVIDIA GeForce RTX 2070], DRIVER_VENDOR=NVIDIA, DRIVER_VERSION=27.21.14.5671 ACTIVE GPU1: VENDOR= 0x1414, DEVICE=0x008c [Microsoft Basic Render Driver], DRIVER_VERSION=10.0.26100.8246 Machine model name: Machine model version: direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off trees_in_viz: disabled_off video_decode: enabled video_encode: enabled webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	31.93GB (18.95GB free)
Process Argv	--crash-reporter-id e410d60b-c196-4fda-9bf0-3429e57343ac
Screen Reader	no
VM	0%

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