Merge main into features/collection-expression-arguments. (#80510)

.github/copilot-instructions.md

@@ -54,6 +54,10 @@ var symbolInfo = semanticModel.GetSymbolInfo(expression);
 - Test utilities in `Microsoft.CodeAnalysis.Test.Utilities`
 - Language-specific test bases: `CSharpTestBase`, `VisualBasicTestBase`
 - Add `[WorkItem("https://github.com/dotnet/roslyn/issues/issueNumber")]` attribute to tests that fix specific GitHub issues
+- Prefer raw string literals (`"""..."""`) over verbatim strings (`@"..."`) when creating test source code
+- Avoid unnecessary intermediary assertions - tests should do the minimal amount of work to validate just the core issue being addressed
+  - In tests, use concise methods like `.Single()` instead of asserting count and extracting elements
+  - For compiler tests, validate diagnostics (e.g., `comp.VerifyEmitDiagnostics()`) so reviewers can easily see if the code is in error or represents something legal
 
 ## Critical Integration Points
 

.github/instructions/Compiler.instructions.md

@@ -60,6 +60,7 @@ dotnet run --file eng/generate-compiler-code.cs
 - **Unit tests**: Test individual compiler phases (lexing, parsing)
 - **Compilation tests**: Create `Compilation` objects and verify symbols/diagnostics
 - **Cross-language patterns**: Many test patterns work for both C# and VB with minor syntax changes
+- **Keep tests focused**: Avoid unnecessary assertions. Tests should do the minimal work necessary to get to the core assertions that validate the issue being addressed. For example, use `Single()` instead of checking counts and then accessing the first element.
 
 ## Debugger Integration
 

docs/compilers/CSharp/Compiler Breaking Changes - DotNet 11.md

@@ -1,6 +1,64 @@
-# Breaking changes in Roslyn after .NET 10.0.100 through .NET 11 (version number tbd)
+# Breaking changes in Roslyn after .NET 10.0.100 through .NET 11.0.100
 
-This document lists known breaking changes in Roslyn after .NET 10 general release (.NET SDK version 10.0.100) through .NET 11 general release (.NET SDK version TBD).
+This document lists known breaking changes in Roslyn after .NET 10 general release (.NET SDK version 10.0.100) through .NET 11 general release (.NET SDK version 11.0.100).
+
+## The *safe-context* of a collection expression of Span/ReadOnlySpan type is now *declaration-block*
+
+***Introduced in Visual Studio 2026 version 18.3***
+
+The C# compiler made a breaking change in order to properly adhere to the [ref safety rules](https://github.com/dotnet/csharplang/blob/main/proposals/csharp-12.0/collection-expressions.md#ref-safety) in the *collection expressions* feature specification. Specifically, the following clause:
+
+> * If the target type is a *span type* `System.Span<T>` or `System.ReadOnlySpan<T>`, the safe-context of the collection expression is the *declaration-block*.
+
+Previously, the compiler used safe-context *function-member* in this situation. We have now made a change to use *declaration-block* per the specification. This can cause new errors to appear in existing code, such as in the scenario below:
+
+```cs
+scoped Span<int> items1 = default;
+scoped Span<int> items2 = default;
+foreach (var x in new[] { 1, 2 })
+{
+    Span<int> items = [x];
+    if (x == 1)
+        items1 = items; // previously allowed, now an error
+
+    if (x == 2)
+        items2 = items; // previously allowed, now an error
+}
+```
+
+If your code is impacted by this breaking change, consider using an array type for the relevant collection expressions instead:
+
+```cs
+scoped Span<int> items1 = default;
+scoped Span<int> items2 = default;
+foreach (var x in new[] { 1, 2 })
+{
+    int[] items = [x];
+    if (x == 1)
+        items1 = items; // ok, using 'int[]' conversion to 'Span<int>'
+
+    if (x == 2)
+        items2 = items; // ok
+}
+```
+
+Alternatively, move the collection-expression to a scope where the assignment is permitted:
+```cs
+scoped Span<int> items1 = default;
+scoped Span<int> items2 = default;
+Span<int> items = [0];
+foreach (var x in new[] { 1, 2 })
+{
+    items[0] = x;
+    if (x == 1)
+        items1 = items; // ok
+
+    if (x == 2)
+        items2 = items; // ok
+}
+```
+
+See also https://github.com/dotnet/csharplang/issues/9750.
 
 ## `with()` as a collection expression element is treated as collection construction *arguments*
 
@@ -19,4 +77,4 @@ object[] items;
 items = [with(x, y), z];  // C#14: call to with() method; PROTOTYPE C#14: error args not supported for object[]
 items = [@with(x, y), z]; // call to with() method
 object with(object a, object b) { ... }
-```
+```

docs/compilers/CSharp/Warnversion Warning Waves.md

@@ -36,7 +36,7 @@ The compiler shipped with .NET 7 (the C# 11 compiler) contains the following war
 
 | Warning ID | Description |
 |------------|-------------|
-| CS8981 | [Type names only containing lower-cased ascii characters may become reserved for the language](https://github.com/dotnet/roslyn/issues/56653) |
+| CS8981 | [Type names only containing lowercase ASCII characters may become reserved for the language](https://github.com/dotnet/roslyn/issues/56653) |
 
 ## Warning level 6
 

docs/contributing/Developing a Language Feature.md

@@ -42,7 +42,7 @@ This page discusses the process by which language feature *implementations* are
     left some language details unspecified, to be resolved based
     on implementation experience, or when experience with the prototype suggests that some language design
     decisions should be reconsidered. 
-    * **Closed**: The feature hit unforeseen design issues, implementation road blocks, etc. that caused it to be removed.
+    * **Closed**: The feature hit unforeseen design issues, implementation roadblocks, etc. that caused it to be removed.
 
 1. **Finishing**: Once a feature is integrated into the main tree, it's time to lock down and finish the implementation. This includes any remaining areas not completed in the prototype, and completing all of the corner cases and tests (lots and lots of tests!).  
 
@@ -52,7 +52,7 @@ This page discusses the process by which language feature *implementations* are
 
 It's important to note there are **no guarantees** about a feature being a part of the language until it has reached the 'Acceptance' state **and** shipped in an official build. Features in any other state--no matter how complete--can be pulled at the last minute if the Language Team deems it's necessary to do so.  
 
-Pulling a feature after the prototype phase completes is not a decision the Langauge Team takes lightly; however, in the past, unforeseen circumstances have caused us to do so. The best example of this was the decision to pull parameterless struct constructors very late in the C# 6.0 timeframe.  
+Pulling a feature after the prototype phase completes is not a decision the Language Team takes lightly; however, in the past, unforeseen circumstances have caused us to do so. The best example of this was the decision to pull parameterless struct constructors very late in the C# 6.0 timeframe.  
 
 ## Community Contributions
 The intent of this document is to codify the process used by the Language Team to implement language features so that the community can contribute implementations. Community members can contribute to ongoing prototypes or in some cases be the primary driver of the prototype.  
@@ -66,7 +66,7 @@ Community members who wish to drive a particular feature can request so by comme
 
 - **Why are features disabled by default?**: Language features spend a considerable amount of time in the same branch as our shipping product which is often main.  The main branch of Roslyn is kept in a ship ready state at all times.  To facilitate this all features which haven't been fully accepted into the language must be disabled.
 
-- **What is the difference between the feature and main branches?**: The main branch represents code which will ship in updates to the current version of the compiler.  The feature branches represents each feature which are still in progress, therefore not merged yet.
+- **What is the difference between the feature and main branches?**: The main branch represents code which will ship in updates to the current version of the compiler. The feature branches represent features that are still in progress, therefore not merged yet.
 
 - **Why weren't speclets filed for early features?**: Features such as tuples and local functions were done before this process was fully developed.  Their speclets were considered internally and eventually became the `docs/feature/<feature name.md>` file.
 

docs/features/tuples.md

@@ -75,7 +75,7 @@ var t1 = new (int sum, int count) (0, 1);
 var t2 = new (int sum, int count) { sum = 0, count = 0 };
 var t3 = new (int, int) (0, 1);     // field names are optional    
 ```
-Note that specifying field names is optional, however when names are provided, all fields must be named. Duplicate names are disallowed.
+Note that specifying field names is optional; however, when names are provided, all fields must be named. Duplicate names are disallowed.
 
 Tuple literals
 --------------
@@ -99,7 +99,7 @@ Note that specifying field names is optional, however when names are provided, a
 
 
 ```C#
-var t1 = (sum: 0, 1);		// error! some fields are named some are not.
+var t1 = (sum: 0, 1);		// error! Some fields are named, some are not.
 var t2 = (sum: 0, sum: 1);	// error! duplicate names.
 ```
 

docs/wiki/Diagnosing-Project-System-Build-Errors.md

@@ -58,7 +58,7 @@ you'll see a bunch of files that end in `.designtime.log`.
 
   `Project "c:\Projects\ConsoleApplication53\ConsoleApplication53\ConsoleApplication53.csproj" (Compile target(s)):`
 
-  This shows the full name of the project, along with the target (Compile) being ran. Once again, look for the "Compile"
+  This shows the full name of the project, along with the target (Compile) being run. Once again, look for the "Compile"
   target. There are files with other targets being invoked, you'll want to ignore those. You might want to consider
   using Visual Studio's "find in files" feature to find the right file.
 
@@ -67,15 +67,15 @@ see something like this:
 
     Build FAILED.
 
-    c:\ConsoleApplication53\ConsoleApplication53\ConsoleApplication53.csproj(17,5): error : An error occured!
+    c:\ConsoleApplication53\ConsoleApplication53\ConsoleApplication53.csproj(17,5): error : An error occurred!
         0 Warning(s)
         1 Error(s)
 
-Notably, you should see `Build FAILED` and then one or more errors. This is summary of the errors in the log, so if you
+Notably, you should see `Build FAILED` and then one or more errors. This is a summary of the errors in the log, so if you
 do see an error, you should now search this log file for that error and find out where it is. Hopefully, the error will
 give some sort of a hint; it's looking for some file or SDK that's not installed, or some permissions were denied, etc.
 In that case, you can follow up with the owner of that to figure out what went wrong.
 
 If it seems to be a problem with Visual Studio itself, you might want to file a bug on
-[the Roslyn GitHub project](https://github.com/dotnet/roslyn) have a Visual Studio engineer take a look. Make sure you
+[the Roslyn GitHub project](https://github.com/dotnet/roslyn) to have a Visual Studio engineer take a look. Make sure you
 provide the full log and if possible your project file, since we may need both to diagnose the problem.

eng/Version.Details.props

@@ -38,9 +38,9 @@ This file should be imported by eng/Versions.props
     <SystemThreadingTasksDataflowPackageVersion>9.0.0</SystemThreadingTasksDataflowPackageVersion>
     <SystemWindowsExtensionsPackageVersion>9.0.0</SystemWindowsExtensionsPackageVersion>
     <!-- dotnet/arcade dependencies -->
-    <MicrosoftDotNetArcadeSdkPackageVersion>11.0.0-beta.25509.1</MicrosoftDotNetArcadeSdkPackageVersion>
-    <MicrosoftDotNetHelixSdkPackageVersion>11.0.0-beta.25509.1</MicrosoftDotNetHelixSdkPackageVersion>
-    <MicrosoftDotNetXliffTasksPackageVersion>11.0.0-beta.25509.1</MicrosoftDotNetXliffTasksPackageVersion>
+    <MicrosoftDotNetArcadeSdkPackageVersion>11.0.0-beta.25522.1</MicrosoftDotNetArcadeSdkPackageVersion>
+    <MicrosoftDotNetHelixSdkPackageVersion>11.0.0-beta.25522.1</MicrosoftDotNetHelixSdkPackageVersion>
+    <MicrosoftDotNetXliffTasksPackageVersion>11.0.0-beta.25522.1</MicrosoftDotNetXliffTasksPackageVersion>
     <!-- dotnet/symreader dependencies -->
     <MicrosoftDiaSymReaderPackageVersion>2.0.0</MicrosoftDiaSymReaderPackageVersion>
     <!-- dotnet/roslyn-analyzers dependencies -->

eng/Version.Details.xml

@@ -115,13 +115,13 @@
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>
-    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="11.0.0-beta.25509.1">
+    <Dependency Name="Microsoft.DotNet.Arcade.Sdk" Version="11.0.0-beta.25522.1">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>488413fe104056170673a048a07906314e101e5d</Sha>
+      <Sha>c02d02ff59dddbf4d9ad1f32fdc42dec5871af44</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.XliffTasks" Version="11.0.0-beta.25509.1">
+    <Dependency Name="Microsoft.DotNet.XliffTasks" Version="11.0.0-beta.25522.1">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>488413fe104056170673a048a07906314e101e5d</Sha>
+      <Sha>c02d02ff59dddbf4d9ad1f32fdc42dec5871af44</Sha>
     </Dependency>
     <Dependency Name="Microsoft.DiaSymReader" Version="2.0.0">
       <Uri>https://github.com/dotnet/symreader</Uri>
@@ -131,9 +131,9 @@
       <Uri>https://github.com/dotnet/roslyn</Uri>
       <Sha>5d10d428050c0d6afef30a072c4ae68776621877</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.Helix.Sdk" Version="11.0.0-beta.25509.1">
+    <Dependency Name="Microsoft.DotNet.Helix.Sdk" Version="11.0.0-beta.25522.1">
       <Uri>https://github.com/dotnet/arcade</Uri>
-      <Sha>488413fe104056170673a048a07906314e101e5d</Sha>
+      <Sha>c02d02ff59dddbf4d9ad1f32fdc42dec5871af44</Sha>
     </Dependency>
     <Dependency Name="Microsoft.CodeAnalysis.NetAnalyzers" Version="10.0.0-preview.25375.1">
       <Uri>https://github.com/dotnet/roslyn-analyzers</Uri>

eng/Versions.props

@@ -108,7 +108,7 @@
     Analyzer, it needs to directly reference patched versions of some transitive dependencies.
   -->
   <PropertyGroup>
-    <MicrosoftBuildTasksCoreVersionForMetrics>17.10.29</MicrosoftBuildTasksCoreVersionForMetrics>
+    <MicrosoftBuildTasksCoreVersionForMetrics>17.11.48</MicrosoftBuildTasksCoreVersionForMetrics>
     <SystemTextJsonVersionForMetrics>8.0.5</SystemTextJsonVersionForMetrics>
   </PropertyGroup>
   <PropertyGroup>

eng/build.ps1

@@ -734,15 +734,6 @@ try {
 
   Push-Location $RepoRoot
 
-  # Workaround for DOTNET_HOST_PATH not being set by older MSBuild
-  # Removal is tracked by https://github.com/dotnet/roslyn/issues/80742
-  if (-not $env:DOTNET_HOST_PATH) {
-    $env:DOTNET_HOST_PATH = Join-Path (Join-Path $RepoRoot '.dotnet') 'dotnet'
-    if (-not (Test-Path $env:DOTNET_HOST_PATH)) {
-      $env:DOTNET_HOST_PATH = "$($env:DOTNET_HOST_PATH).exe"
-    }
-  }
-
   Subst-TempDir
 
   if ($ci) {
@@ -759,6 +750,19 @@ try {
     &(Ensure-DotNetSdk) tool restore
   }
 
+  # Above InitializeDotNetCli or Ensure-DotNetSdk may have installed a local .NET SDK.
+  # $global:_DotNetInstallDir will point to the correct global or local SDK location.
+  # We need to make sure DOTNET_HOST_PATH points to that SDK as a workaround for older MSBuild
+  # which will not set it correctly.  Removal is tracked by https://github.com/dotnet/roslyn/issues/80742
+  if (-not $env:DOTNET_HOST_PATH -and (Test-Path variable:global:_DotNetInstallDir)) {
+    $env:DOTNET_HOST_PATH = Join-Path $global:_DotNetInstallDir 'dotnet'
+    if (-not (Test-Path $env:DOTNET_HOST_PATH)) {
+      $env:DOTNET_HOST_PATH = "$($env:DOTNET_HOST_PATH).exe"
+    }
+
+    Write-Host "Setting DOTNET_HOST_PATH to $env:DOTNET_HOST_PATH"
+  }
+
   if ($bootstrap -and $bootstrapDir -eq "") {
     Write-Host "Building bootstrap Compiler"
     $bootstrapDir = Join-Path (Join-Path $ArtifactsDir "bootstrap") "build"

eng/common/SetupNugetSources.sh

@@ -66,10 +66,8 @@ EnableInternalPackageSource() {
     grep -i "<add key=\"$PackageSourceName\" value=\"true\"" "$ConfigFile" > /dev/null
     if [ "$?" == "0" ]; then
         echo "Enabling internal source '$PackageSourceName'."
-        # Remove the disabled entry
-        local OldDisableValue="<add key=\"$PackageSourceName\" value=\"true\" />"
-        local NewDisableValue="<!-- Reenabled for build : $PackageSourceName -->"
-        sed -i.bak "s|$OldDisableValue|$NewDisableValue|" "$ConfigFile"
+        # Remove the disabled entry (including any surrounding comments or whitespace on the same line)
+        sed -i.bak "/<add key=\"$PackageSourceName\" value=\"true\" \/>/d" "$ConfigFile"
 
         # Add the source name to PackageSources for credential handling
         PackageSources+=("$PackageSourceName")

eng/common/core-templates/job/publish-build-assets.yml

@@ -91,8 +91,8 @@ jobs:
       fetchDepth: 3
       clean: true
 
-    - ${{ if eq(parameters.isAssetlessBuild, 'false') }}: 
-      - ${{ if eq(parameters.publishingVersion, 3) }}: 
+    - ${{ if eq(parameters.isAssetlessBuild, 'false') }}:
+      - ${{ if eq(parameters.publishingVersion, 3) }}:
         - task: DownloadPipelineArtifact@2
           displayName: Download Asset Manifests
           inputs:
@@ -117,9 +117,16 @@ jobs:
             flattenFolders: true
           condition: ${{ parameters.condition }}
           continueOnError: ${{ parameters.continueOnError }}
-    
+
     - task: NuGetAuthenticate@1
 
+    # Populate internal runtime variables.
+    - template: /eng/common/templates/steps/enable-internal-sources.yml
+      parameters:
+        legacyCredential: $(dn-bot-dnceng-artifact-feeds-rw)
+
+    - template: /eng/common/templates/steps/enable-internal-runtimes.yml
+
     - task: AzureCLI@2
       displayName: Publish Build Assets
       inputs:
@@ -132,9 +139,12 @@ jobs:
           /p:IsAssetlessBuild=${{ parameters.isAssetlessBuild }}
           /p:MaestroApiEndpoint=https://maestro.dot.net
           /p:OfficialBuildId=$(OfficialBuildId)
+          -runtimeSourceFeed https://ci.dot.net/internal
+          -runtimeSourceFeedKey $(dotnetbuilds-internal-container-read-token-base64)
+
       condition: ${{ parameters.condition }}
       continueOnError: ${{ parameters.continueOnError }}
-    
+
     - task: powershell@2
       displayName: Create ReleaseConfigs Artifact
       inputs:
@@ -162,7 +172,7 @@ jobs:
             artifactName: AssetManifests
             displayName: 'Publish Merged Manifest'
             retryCountOnTaskFailure: 10 # for any logs being locked
-            sbomEnabled: false  # we don't need SBOM for logs
+            sbomEnabled: false # we don't need SBOM for logs
 
     - template: /eng/common/core-templates/steps/publish-build-artifacts.yml
       parameters:
@@ -195,9 +205,11 @@ jobs:
             -ArtifactsPublishingAdditionalParameters '${{ parameters.artifactsPublishingAdditionalParameters }}'
             -SymbolPublishingAdditionalParameters '${{ parameters.symbolPublishingAdditionalParameters }}'
             -SkipAssetsPublishing '${{ parameters.isAssetlessBuild }}'
+            -runtimeSourceFeed https://ci.dot.net/internal 
+            -runtimeSourceFeedKey $(dotnetbuilds-internal-container-read-token-base64)
 
     - ${{ if eq(parameters.enablePublishBuildArtifacts, 'true') }}:
       - template: /eng/common/core-templates/steps/publish-logs.yml
         parameters:
           is1ESPipeline: ${{ parameters.is1ESPipeline }}
-          JobLabel: 'Publish_Artifacts_Logs'     
+          JobLabel: 'Publish_Artifacts_Logs'