Merge pull request #1288 from microsoft/fix1205

Avoid using `UnscopedRefAttribute` on downlevel *compilers*
microsoft · Sep 27, 2024 · 748f605 · 748f605
2 parents 7327da2 + d679d95
commit 748f605
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Showing 3 changed files with 11 additions and 0 deletions.
diff --git a/src/Microsoft.Windows.CsWin32/Generator.Features.cs b/src/Microsoft.Windows.CsWin32/Generator.Features.cs
@@ -5,6 +5,7 @@ namespace Microsoft.Windows.CsWin32;
 
 public partial class Generator
 {
+    private readonly bool canUseUnscopedRef;
     private readonly bool canUseSpan;
     private readonly bool canCallCreateSpan;
     private readonly bool canUseUnsafeAsRef;

diff --git a/src/Microsoft.Windows.CsWin32/Generator.cs b/src/Microsoft.Windows.CsWin32/Generator.cs
@@ -85,6 +85,11 @@ public Generator(string metadataLibraryPath, Docs? docs, GeneratorOptions option
         this.parseOptions = parseOptions;
         this.volatileCode = new(this.committedCode);
 
+        // UnscopedRefAttribute may be emitted to work on downlevel *runtimes*, but we can't use it
+        // on downlevel *compilers*. Only .NET 8+ SDK compilers support it. Since we cannot detect
+        // compiler version, we use language version instead.
+        this.canUseUnscopedRef = this.parseOptions?.LanguageVersion >= (LanguageVersion)1100; // C# 11.0
+
         this.canUseSpan = this.compilation?.GetTypeByMetadataName(typeof(Span<>).FullName) is not null;
         this.canCallCreateSpan = this.compilation?.GetTypeByMetadataName(typeof(MemoryMarshal).FullName)?.GetMembers("CreateSpan").Any() is true;
         this.canUseUnsafeAsRef = this.compilation?.GetTypeByMetadataName(typeof(Unsafe).FullName)?.GetMembers("Add").Any() is true;
@@ -117,6 +122,7 @@ public Generator(string metadataLibraryPath, Docs? docs, GeneratorOptions option
             AddSymbolIf(this.canUseUnsafeNullRef, "canUseUnsafeNullRef");
             AddSymbolIf(compilation?.GetTypeByMetadataName("System.Drawing.Point") is not null, "canUseSystemDrawing");
             AddSymbolIf(this.IsFeatureAvailable(Feature.InterfaceStaticMembers), "canUseInterfaceStaticMembers");
+            AddSymbolIf(this.canUseUnscopedRef, "canUseUnscopedRef");
 
             if (extraSymbols.Count > 0)
             {

diff --git a/src/Microsoft.Windows.CsWin32/templates/VariableLengthInlineArray`1.cs b/src/Microsoft.Windows.CsWin32/templates/VariableLengthInlineArray`1.cs
@@ -3,6 +3,8 @@
 {
 	internal T e0;
 
+#if canUseUnscopedRef
+
 #if canUseUnsafeAdd
 	internal ref T this[int index]
 	{
@@ -30,4 +32,6 @@ internal Span<T> AsSpan(int length)
 #endif
 	}
 #endif
+
+#endif
 }