Fix visibility of macros

Author: AArnott

src/Microsoft.Windows.CsWin32/Generator.cs

@@ -1605,7 +1605,7 @@ internal void RequestMacro(MethodDeclarationSyntax macro)
     {
         this.volatileCode.GenerateMacro(macro.Identifier.ValueText, delegate
         {
-            this.volatileCode.AddMacro(macro.Identifier.ValueText, macro);
+            this.volatileCode.AddMacro(macro.Identifier.ValueText, (MethodDeclarationSyntax)ElevateVisibility(macro));
 
             // Generate any additional types that this macro relies on.
             foreach (QualifiedNameSyntax identifier in macro.DescendantNodes().OfType<QualifiedNameSyntax>())

test/Microsoft.Windows.CsWin32.Tests/GeneratorTests.cs

@@ -607,6 +607,18 @@ public void HandleStructsHaveStaticNullMember(string handleName)
         this.AssertGeneratedMember(handleName, "Null", $"internal static {handleName} Null => default;");
     }
 
+    [Theory, PairwiseData]
+    public void MacroAPIsGenerateWithAppropriateVisibility(bool publicVisibility)
+    {
+        this.generator = this.CreateGenerator(DefaultTestGeneratorOptions with { Public = publicVisibility });
+        Assert.True(this.generator.TryGenerate("HRESULT_FROM_WIN32", CancellationToken.None));
+        this.CollectGeneratedCode(this.generator);
+        this.AssertNoDiagnostics();
+        var method = Assert.Single(this.FindGeneratedMethod("HRESULT_FROM_WIN32"));
+
+        Assert.True(method.Modifiers.Any(publicVisibility ? SyntaxKind.PublicKeyword : SyntaxKind.InternalKeyword));
+    }
+
     [Theory]
     [InlineData("HRESULT_FROM_WIN32")]
     public void MacroAPIsGenerate(string macro)