Fix #44 Ensure generic member access preserves its type arguments

src/Zomp.SyncMethodGenerator/AsyncToSyncRewriter.cs

@@ -360,7 +360,7 @@ bool IsValidParameter(ParameterSyntax ps)
         }
         else if (@base.Name.Identifier.ValueText.EndsWithAsync())
         {
-            return @base.WithName(SyntaxFactory.IdentifierName(RemoveAsync(@base.Name.Identifier.ValueText)));
+            return @base.WithName(@base.ChangeIdentifier(RemoveAsync(@base.Name.Identifier.ValueText)));
         }
 
         return @base;
@@ -1222,27 +1222,22 @@ private static InvocationExpressionSyntax UnwrapExtension(InvocationExpressionSy
             newName = RemoveAsync(newName);
         }
 
-        var id = Identifier($"{MakeType(reducedFrom.ContainingType)}.{newName}");
+        var fullyQualifiedName = $"{MakeType(reducedFrom.ContainingType)}.{newName}";
 
-        ExpressionSyntax es = ies.Expression is MemberAccessExpressionSyntax { Name: GenericNameSyntax gns }
-            ? GenericName(id, gns.TypeArgumentList)
-            : IdentifierName(id);
+        var es = ies.Expression is MemberAccessExpressionSyntax mae
+            ? mae.ChangeIdentifier(fullyQualifiedName)
+            : IdentifierName(Identifier(fullyQualifiedName));
 
         return ies
             .WithExpression(es)
             .WithArgumentList(ArgumentList(newList));
     }
 
-    private static string? GetNewName(IMethodSymbol methodSymbol)
+    private static string GetNewName(IMethodSymbol methodSymbol)
     {
         var containingType = methodSymbol.ContainingType;
         var replacement = Regex.Replace(methodSymbol.Name, "Memory", "Span");
         var newSymbol = containingType.GetMembers().FirstOrDefault(z => z.Name == replacement);
-        if (newSymbol is null)
-        {
-            return null;
-        }
-
         return replacement;
     }
 

src/Zomp.SyncMethodGenerator/Extensions.cs

@@ -37,6 +37,13 @@ internal static T AppendSpace<T>(this T syntax)
         where T : ExpressionSyntax
         => syntax.WithTrailingTrivia(Space);
 
+    internal static SimpleNameSyntax ChangeIdentifier(this MemberAccessExpressionSyntax mae, string id)
+    {
+        return mae is { Name: GenericNameSyntax gns }
+            ? GenericName(Identifier(id), gns.TypeArgumentList)
+            : IdentifierName(Identifier(id));
+    }
+
     internal static BlockSyntax CreateBlock(this ICollection<StatementSyntax> statements, int indentationLevel = 0)
     {
         var list = new List<StatementSyntax>();

tests/Generator.Tests/Snapshots/UnitTests.GenericAsyncCall#Test.GenericClass.FooAsync.g.verified.cs

@@ -0,0 +1,9 @@
+//HintName: Test.GenericClass.FooAsync.g.cs
+// <auto-generated/>
+#nullable enable
+namespace Test;
+partial class GenericClass<T>
+{
+    public T Foo<T>()
+        => this.InnerFoo<T>();
+}

tests/Generator.Tests/UnitTests.cs

@@ -74,6 +74,20 @@ public async Task MethodAsync()
     }
 }
 
+""".Verify(sourceType: SourceType.Full);
+
+    [Fact]
+    public Task GenericAsyncCall() => """
+namespace Test;
+partial class GenericClass<T>
+{
+    [CreateSyncVersion]
+    public async Task<T> FooAsync<T>(CancellationToken ct = default)
+        => await this.InnerFooAsync<T>(ct);
+
+    private async Task<T> InnerFooAsync<T>(CancellationToken ct = default) => default;
+    private async T InnerFoo<T>() => default;
+}
 """.Verify(sourceType: SourceType.Full);
 
     [Fact]