Clean up MethodParameter

- Enable nullability
- Add constructors
- Make properties read-only

Author: DustinCampbell

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/CodeGeneration/DefaultDocumentWriterTest.cs

@@ -309,21 +309,8 @@ public void WriteDocument_WritesMethod()
             Modifiers = ["internal", "virtual", "async"],
             MethodName = "TestMethod",
             Parameters = [
-                new MethodParameter()
-                {
-                    Modifiers =
-                    {
-                        "readonly",
-                        "ref",
-                    },
-                    ParameterName = "a",
-                    TypeName = "int",
-                },
-                new MethodParameter()
-                {
-                    ParameterName = "b",
-                    TypeName = "string",
-                }
+                new MethodParameter(modifiers: ["readonly", "ref"], typeName: "int", parameterName: "a"),
+                new MethodParameter(typeName: "string", parameterName: "b")
             ],
             ReturnType = "string",
         });

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/CodeGeneration/DefaultDocumentWriter.cs

@@ -174,9 +174,9 @@ public override void VisitMethodDeclaration(MethodDeclarationIntermediateNode no
                     codeWriter.Write(", ");
                 }
 
-                for (var j = 0; j < parameter.Modifiers.Count; j++)
+                foreach (var modifier in parameter.Modifiers)
                 {
-                    codeWriter.Write($"{parameter.Modifiers[j]} ");
+                    codeWriter.Write($"{modifier} ");
                 }
 
                 codeWriter.Write($"{parameter.TypeName} {parameter.ParameterName}");

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/ComponentDocumentClassifierPass.cs

@@ -141,11 +141,9 @@ protected override void OnDocumentStructureCreated(
             method.MethodName = ComponentsApi.ComponentBase.BuildRenderTree;
             method.UpdateModifiers("protected", "override");
 
-            method.UpdateParameters(new MethodParameter()
-            {
-                ParameterName = ComponentsApi.RenderTreeBuilder.BuilderParameter,
-                TypeName = $"global::{ComponentsApi.RenderTreeBuilder.FullTypeName}",
-            });
+            method.UpdateParameters(new MethodParameter(
+                typeName: $"global::{ComponentsApi.RenderTreeBuilder.FullTypeName}",
+                parameterName: ComponentsApi.RenderTreeBuilder.BuilderParameter));
         }
     }
 

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Intermediate/MethodParameter.cs

@@ -1,17 +1,18 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
-using System.Collections.Generic;
+using System.Collections.Immutable;
 
 namespace Microsoft.AspNetCore.Razor.Language.Intermediate;
 
-public sealed class MethodParameter
+public sealed class MethodParameter(ImmutableArray<string> modifiers, string typeName, string parameterName)
 {
-    public IList<string> Modifiers { get; } = new List<string>();
-
-    public string TypeName { get; set; }
+    public ImmutableArray<string> Modifiers { get; } = modifiers.NullToEmpty();
+    public string TypeName { get; } = typeName;
+    public string ParameterName { get; } = parameterName;
 
-    public string ParameterName { get; set; }
+    public MethodParameter(string typeName, string parameterName)
+        : this(modifiers: [], typeName, parameterName)
+    {
+    }
 }