Test dynamic member tooltip rendering

Lock the hover content the dynamic-tooltip work produces. Ambience-level
cases (CSharpAmbienceTests) pin that SpecialType.Dynamic renders as
"dynamic" and that a synthetic dynamic method renders its return and
per-argument types - including the full hover form, confirming the
unnamed synthetic parameters collapse to their types with no dangling
name. An end-to-end case (HoverOnlyReferenceTests) decompiles a dynamic
call and renders the symbol GetSymbol hands back, exercising the actual
synthesis (argument typing from the callsite delegate), not a hand-built
stand-in.

Assisted-by: Claude:claude-fable-5:Claude Code

ICSharpCode.Decompiler.Tests/Output/CSharpAmbienceTests.cs

@@ -323,6 +323,40 @@ namespace ICSharpCode.Decompiler.Tests.Output
 		}
 		#endregion
 
+		#region Dynamic (synthesized member) tests
+		[Test]
+		public void DynamicType()
+		{
+			ambience.ConversionFlags = ConversionFlags.None;
+			Assert.That(ambience.ConvertType(SpecialType.Dynamic), Is.EqualTo("dynamic"));
+		}
+
+		[Test]
+		public void DynamicInvokeMember()
+		{
+			// The shape ExpressionBuilder synthesizes for a.Compute(1, "two", d): dynamic return,
+			// per-argument types from the callsite delegate (constants keep their compile-time type),
+			// declared on the dynamic type.
+			var method = new FakeMethod(compilation, SymbolKind.Method) {
+				Name = "Compute",
+				ReturnType = SpecialType.Dynamic,
+				DeclaringType = SpecialType.Dynamic,
+				Parameters = new IParameter[] {
+					new DefaultParameter(compilation.FindType(KnownTypeCode.Int32), string.Empty),
+					new DefaultParameter(compilation.FindType(KnownTypeCode.String), string.Empty),
+					new DefaultParameter(SpecialType.Dynamic, string.Empty),
+				},
+			};
+			ambience.ConversionFlags = ConversionFlags.ShowReturnType | ConversionFlags.ShowParameterList;
+			Assert.That(ambience.ConvertSymbol(method), Is.EqualTo("dynamic Compute(int, string, dynamic)"));
+
+			// The same member as DecompilerTextView.BuildHoverContent renders it (full hover form): the
+			// unnamed synthetic parameters collapse to their types, so there is no dangling-name artifact.
+			ambience.ConversionFlags = ConversionFlags.All & ~(ConversionFlags.ShowBody | ConversionFlags.PlaceReturnTypeAfterParameterList);
+			Assert.That(ambience.ConvertSymbol(method), Is.EqualTo("public dynamic dynamic.Compute(int, string, dynamic)"));
+		}
+		#endregion
+
 		#region Test types
 #pragma warning disable 169, 67
 

ILSpy.Tests/Editor/HoverOnlyReferenceTests.cs

@@ -24,6 +24,9 @@ using Avalonia.VisualTree;
 
 using AwesomeAssertions;
 
+using ICSharpCode.Decompiler.CSharp.OutputVisitor;
+using ICSharpCode.Decompiler.Output;
+using ICSharpCode.Decompiler.TypeSystem;
 using ICSharpCode.ILSpy.TextView;
 using ICSharpCode.ILSpy.TreeNodes;
 
@@ -41,6 +44,11 @@ public class DynamicMemberSample
 	{
 		return d.Property;
 	}
+
+	public object Call(dynamic d)
+	{
+		return d.Compute(1, "two", d);
+	}
 }
 
 /// <summary>
@@ -76,4 +84,31 @@ public class HoverOnlyReferenceTests
 		navigated.Should().BeFalse("clicking a hover-only reference must not navigate");
 		view.LocalReferenceMarks.Should().BeEmpty("a hover-only reference must not highlight occurrences");
 	}
+
+	[AvaloniaTest]
+	public async Task Dynamic_Invoke_Member_Hover_Renders_Its_Synthesized_Signature()
+	{
+		var (_, vm) = await TestHarness.BootAsync();
+		await vm.OpenAssemblyAsync(typeof(DynamicMemberSample).Assembly.Location);
+		var typeNode = vm.AssemblyTreeModel.FindNode<TypeTreeNode>(
+			"ILSpy.Tests",
+			"ICSharpCode.ILSpy.Tests.TextView",
+			"ICSharpCode.ILSpy.Tests.TextView.DynamicMemberSample");
+		vm.AssemblyTreeModel.SelectNode(typeNode);
+		var tab = await vm.DockWorkspace.WaitForDecompiledTextAsync();
+
+		// The 'Compute' hover target is the member synthesized for the dynamic call d.Compute(1, "two", d).
+		var compute = tab.References!
+			.Select(r => r.Reference)
+			.OfType<IMethod>()
+			.First(m => m.Name == "Compute");
+
+		var ambience = new CSharpAmbience {
+			ConversionFlags = ConversionFlags.ShowReturnType | ConversionFlags.ShowParameterList,
+		};
+		ambience.ConvertSymbol(compute).Should().Be(
+			"dynamic Compute(int, string, dynamic)",
+			"each argument is typed from the callsite: the constants keep their compile-time type, "
+			+ "the dynamic argument stays dynamic");
+	}
 }