loc: replace reflection-based args with tuple-params + IDictionary overloads

The Message(MessageKey, object?) and RichMessage(MessageKey, object?, ...)
overloads built an args dictionary by reflecting over public properties of
the passed object — anonymous types or [LocArgs]-marked records. Under
NativeAOT the trimmer keeps the ctor + backing fields of the anonymous type
(both reachable from the
ew { … } call site) but drops the property
getters, because nothing statically reads them. GetProperties() then
returned an empty array, MessageFormat threw on {name}, the catch
swallowed the exception, and the raw ICU pattern leaked through to the UI.

This change removes the reflection path entirely and gives callers two
AOT-safe shapes:

  - Message(MessageKey, IDictionary<string, object>?) — explicit dict for
    cases that already have one (or want to share/build one programmatically).
  - Message(MessageKey, (string Name, object Value) arg1,
              params (string Name, object Value)[] more) — compact tuple
    syntax for the common inline case. ValueTuple is a nominal type with
    concrete fields; building a Dictionary<string,object> from tuple
    values needs zero reflection.

Same shape for RichMessage. (RichMessage with tags uses the dict
overload — params must come last, so the tuple variant can't carry
the optional 	ags argument.)

Deleted:
  - ToArgsDictionary + IsAcceptableArgsContainer + _propertyCache
  - The IL2026/IL2070 unconditional-suppression attributes those needed
  - System.Reflection + System.Collections.Concurrent +
    System.Diagnostics.CodeAnalysis usings (now unused)

Migrated callers:
  - Selftest + AppTests localization fixtures (two files)
  - IntlAccessorTests, RichMessageTests
  - SourceRewriter CLI codegen: 	.Message(key, new { name = expr })
    → 	.Message(key, ("name", expr)). Updated SourceRewriterTests.
  - Docs: _pipeline/templates/localization.md.dt narrative and
    _pipeline/apps/localization/App.cs snippets, plus the
    hand-edited docs/reference/localization-howto.md example.

Removed from AOT skip list / docs:
  - Localization_LocaleSwitching no longer needs to be skipped under AOT
    (	ests/Reactor.AppTests.Host/SelfTest/SelfTestRunner.cs).
  - The "Localization with anonymous-type args" row in docs/aot-support.md
    is gone — there's no anonymous-type path left.

Verified:
  - dotnet build src/Reactor clean (AOT warnings as errors).
  - 282 localization unit tests pass.
  - Full JIT selftest: 0 failures.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: codemonkeychris

docs/_pipeline/apps/localization/App.cs

@@ -69,7 +69,7 @@ public override Element Render()
         var title = intl.Message(new MessageKey("App", "title"));
         var greeting = intl.Message(
             new MessageKey("App", "greeting"),
-            new { name = "Alice" });
+            ("name", "Alice"));
 
         return VStack(12,
             TextBlock(title).FontSize(24).Bold(),
@@ -156,7 +156,7 @@ public override Element Render()
                     var title = intl.Message(new MessageKey("App", "title"));
                     var greeting = intl.Message(
                         new MessageKey("App", "greeting"),
-                        new { name = "World" });
+                        ("name", "World"));
                     return VStack(4,
                         TextBlock(title).FontSize(18).Bold(),
                         TextBlock(greeting));

docs/_pipeline/templates/localization.md.dt

@@ -56,7 +56,8 @@ picks up the new locale automatically.
 
 Call `UseIntl()` in any descendant — it is a [hook](hooks.md) — to get the
 `IntlAccessor`. Use `.Message()` to look up translated strings by key. Pass
-arguments as an anonymous object for interpolation:
+arguments as `(name, value)` tuples for interpolation — the compact, AOT-safe
+shape supported by the tuple-params overload:
 
 ```csharp snippet="localization/useintl-messages"
 ```

docs/aot-support.md

@@ -31,7 +31,6 @@ These subsystems compile cleanly with `IsAotCompatible=true` (the warnings are s
 | **DataGrid `AutoColumns<T>`** | Reflects over `T`'s public properties via `TypeRegistry`. The `T` parameter is annotated `[DynamicallyAccessedMembers(PublicProperties)]` so the trimmer keeps the members, but `AutoColumns` ultimately funnels into `TypeRegistry.Resolve`, which is `RequiresUnreferencedCode`. Use explicit `Column<T,V>(…)` definitions instead. | Issue #70 |
 | **`UseObservable` on POCOs** | `ObservableTreeTracker` walks public properties via reflection to subscribe to INPC. Observables built explicitly (`Observable<T>`, `IObservableCollection`) are fine; the implicit-INPC path is not. | Issue #70 |
 | **Form validation** | `FormField`'s default editor resolution goes through `TypeRegistry`. Same caveat as PropertyGrid. | Issue #70 |
-| **Localization with anonymous-type args** | `t.Message(Loc.X, new { count = 3 })` reflects over the anonymous type to build the ICU args dictionary. Use `t.Message(Loc.X, new Dictionary<string, object> { ["count"] = 3 })` under AOT. | Issue #70 |
 | **Navigation state JSON** | `NavigationHandle` serializes deep-link state via `JsonSerializer` without a source-generated context. Custom types that ride through navigation state will fail to serialize under AOT. | Issue #70 |
 | **Component discovery (`ReactorApp.Run<TApp>` reflection paths)** | The instantiation of `TApp` itself is annotated and works. The devtools-only `--list-components` enumeration scans `Assembly.GetTypes`; that path is gated to non-AOT builds. | Issue #70 |
 | **Theme resource lookup (`Theme.X`, `ThemeRef.Resolve`)** | `ThemeRef.Resolve` walks `Application.Current.Resources` + its merged/theme dictionaries. The token records (`Theme.Accent`, `Theme.PrimaryText`, …) construct fine, but at runtime the `XamlControlsResources` entries that `ReactorApplication.xaml` brings in aren't fully populated under AOT — `Resolve` returns `null` for keys that exist under the JIT. Brushes applied via `.Foreground(Theme.X)` will fall back to control defaults. | Issue #70 |

docs/reference/localization-howto.md

@@ -379,7 +379,7 @@ public override Element Render()
 
     return VStack(
         Text(t.Message(Loc.MyComponent.Title)),
-        Text(t.Message(Loc.MyComponent.ItemCount, new { count = items.Count })),
+        Text(t.Message(Loc.MyComponent.ItemCount, ("count", items.Count))),
         Text(t.FormatDate(DateTimeOffset.Now)),
         Text(t.FormatNumber(price)),
         Text(t.FormatList(names, ListFormatType.Conjunction))

src/Reactor.Cli/Loc/SourceRewriter.cs

@@ -76,15 +76,15 @@ private static string BuildReplacement(KeyedLocString entry)
             foreach (var param in icuParams)
             {
                 if (argMap.TryGetValue(param, out var exprText) && param != exprText)
-                    argParts.Add($"{param} = {exprText}");
+                    argParts.Add($"(\"{param}\", {exprText})");
                 else
-                    argParts.Add(param); // direct variable reference
+                    argParts.Add($"(\"{param}\", {param})");
             }
 
             if (argParts.Count > 0)
             {
                 var args = string.Join(", ", argParts);
-                return $"t.Message({locPath}, new {{ {args} }})";
+                return $"t.Message({locPath}, {args})";
             }
         }
 

src/Reactor/Core/Localization/IntlAccessor.cs

@@ -1,8 +1,5 @@
-using System.Collections.Concurrent;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using System.Reflection;
 using System.Text.RegularExpressions;
 using Microsoft.UI.Reactor.Core;
 using Microsoft.UI.Xaml;
@@ -21,7 +18,6 @@ public sealed class IntlAccessor
     private readonly CultureInfo _culture;
     private readonly bool _pseudoLocalize;
     private readonly Dictionary<string, string> _assetCache = new();
-    private static readonly ConcurrentDictionary<Type, PropertyInfo[]> _propertyCache = new();
 
     public IntlAccessor(
         string locale,
@@ -54,7 +50,7 @@ public IntlAccessor(
     /// Loads a string resource by key, then formats it with ICU MessageFormat.
     /// Falls back to the default locale if the key is missing in the current locale.
     /// </summary>
-    public string Message(MessageKey key, object? args = null)
+    public string Message(MessageKey key, IDictionary<string, object>? args = null)
     {
         var pattern = ResolvePattern(key);
         if (pattern is null)
@@ -63,13 +59,9 @@ public string Message(MessageKey key, object? args = null)
         string result;
         try
         {
-            if (args is null)
-                result = _messageCache.Format(Locale, pattern);
-            else
-            {
-                var dict = ToArgsDictionary(args);
-                result = _messageCache.Format(Locale, pattern, dict);
-            }
+            result = args is null
+                ? _messageCache.Format(Locale, pattern)
+                : _messageCache.Format(Locale, pattern, args);
         }
         catch (Exception ex)
         {
@@ -83,6 +75,21 @@ public string Message(MessageKey key, object? args = null)
         return _pseudoLocalize ? PseudoLocalizer.Transform(result) : result;
     }
 
+    /// <summary>
+    /// Compact tuple-args overload for the common case of formatting a single
+    /// message with a handful of ICU placeholders. Builds a plain
+    /// <see cref="Dictionary{TKey, TValue}"/> in-place — no reflection, AOT-safe.
+    /// </summary>
+    /// <example>
+    /// <code>
+    /// t.Message(Greeting, ("name", "World"));
+    /// t.Message(SearchResults, ("count", 0), ("query", "test"));
+    /// </code>
+    /// </example>
+    public string Message(MessageKey key, (string Name, object Value) arg1,
+        params (string Name, object Value)[] more)
+        => Message(key, BuildArgs(arg1, more));
+
     /// <summary>
     /// Formats a message that contains rich text tags (e.g., &lt;bold&gt;text&lt;/bold&gt;),
     /// mapping each tag to an element factory. Returns a GroupElement containing the
@@ -94,7 +101,7 @@ public string Message(MessageKey key, object? args = null)
     /// rendered as plain text (tag markers stripped). Nested tags are not supported — only
     /// the outermost tag is processed.
     /// </remarks>
-    public Element RichMessage(MessageKey key, object? args = null,
+    public Element RichMessage(MessageKey key, IDictionary<string, object>? args = null,
         Dictionary<string, Func<string, Element>>? tags = null)
     {
         var pattern = ResolvePattern(key);
@@ -115,8 +122,7 @@ public Element RichMessage(MessageKey key, object? args = null,
                 // BEFORE formatting so a translator-controlled arg can't
                 // mint a `<link>` tag that ParseRichText would dispatch to a
                 // developer-supplied factory.
-                var dict = ToArgsDictionary(args);
-                var escaped = EscapeForRichTags(dict);
+                var escaped = EscapeForRichTags(args);
                 formatted = _messageCache.Format(Locale, pattern, escaped);
             }
         }
@@ -136,6 +142,16 @@ public Element RichMessage(MessageKey key, object? args = null,
         return ParseRichText(formatted, tags);
     }
 
+    /// <summary>
+    /// Compact tuple-args overload of <see cref="RichMessage(MessageKey, IDictionary{string, object}?, Dictionary{string, Func{string, Element}}?)"/>
+    /// — same allocation profile as the tuple-args <c>Message</c> overload.
+    /// Tags must be supplied via the dict-based overload; this variant is for
+    /// the common case where the developer just wants the formatted text.
+    /// </summary>
+    public Element RichMessage(MessageKey key, (string Name, object Value) arg1,
+        params (string Name, object Value)[] more)
+        => RichMessage(key, BuildArgs(arg1, more));
+
     /// <summary>
     /// Resolves a locale-qualified asset path. Falls back to the unqualified path
     /// if no locale-specific asset exists.
@@ -327,47 +343,16 @@ private static Element ParseRichText(string formatted, Dictionary<string, Func<s
         return null;
     }
 
-    [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "ToArgsDictionary uses reflection on anonymous types for localization args.")]
-    [UnconditionalSuppressMessage("Trimming", "IL2070", Justification = "ToArgsDictionary uses reflection on anonymous types for localization args.")]
-    private static IDictionary<string, object> ToArgsDictionary(object args)
-    {
-        if (args is IDictionary<string, object> dict)
-            return dict;
-
-        // SECURITY (TASK-051): refuse arbitrary DTOs. Anonymous types and the
-        // [LocArgs]-marked record contract are the only accepted shapes;
-        // anything else (e.g. a domain DTO with `AccessToken`/`Email`/...)
-        // would expose every public property to translator-controlled patterns.
-        var type = args.GetType();
-        if (!IsAcceptableArgsContainer(type))
-            throw new ArgumentException(
-                $"Localization args must be an IDictionary<string,object>, an anonymous type, or a record marked with [LocArgs]. Got '{type.FullName}'.",
-                nameof(args));
-
-        var result = new Dictionary<string, object>();
-        var props = _propertyCache.GetOrAdd(type,
-            t => t.GetProperties(BindingFlags.Public | BindingFlags.Instance));
-        foreach (var prop in props)
-        {
-            var value = prop.GetValue(args);
-            if (value is not null)
-                result[prop.Name] = value;
-        }
-        return result;
-    }
-
-    private static bool IsAcceptableArgsContainer(Type type)
+    private static Dictionary<string, object> BuildArgs(
+        (string Name, object Value) arg1,
+        (string Name, object Value)[] more)
     {
-        // Anonymous types are sealed, generic, public-property-only with a
-        // compiler-generated name like `<>f__AnonymousType0`.
-        if (type.Name.StartsWith("<>", StringComparison.Ordinal)) return true;
-        // Allow opt-in via [LocArgs] attribute name match.
-        foreach (var attr in type.GetCustomAttributes(inherit: false))
+        var dict = new Dictionary<string, object>(more.Length + 1)
         {
-            var n = attr.GetType().Name;
-            if (n == "LocArgsAttribute" || n == "LocArgs") return true;
-        }
-        return false;
+            [arg1.Name] = arg1.Value,
+        };
+        foreach (var (k, v) in more) dict[k] = v;
+        return dict;
     }
 
     /// <summary>
@@ -396,7 +381,7 @@ private static string SanitizeBidi(string text)
 
     /// <summary>
     /// HTML-escapes string-valued args before they are substituted into a
-    /// pattern that <see cref="RichMessage"/> will tag-parse. TASK-053.
+    /// pattern that the <c>RichMessage</c> overloads will tag-parse. TASK-053.
     /// Non-string values pass through untouched.
     /// </summary>
     private static IDictionary<string, object> EscapeForRichTags(IDictionary<string, object> args)

tests/Reactor.AppTests.Host/Fixtures/LocalizationFixtures.cs

@@ -136,18 +136,18 @@ public override Element Render()
                 VStack(8,
                     TextBlock(t.Message(AppTitle)).Set(tb => tb.FontSize = 24).AutomationId("LocTitle"),
                     TextBlock(t.Message(Welcome)).AutomationId("LocWelcome"),
-                    TextBlock(t.Message(Greeting, new { name = "World" })).AutomationId("LocGreeting"),
+                    TextBlock(t.Message(Greeting, ("name", "World"))).AutomationId("LocGreeting"),
 
                     // Plural scenarios
-                    TextBlock(t.Message(ItemCount, new { count = 0 })).AutomationId("LocPluralZero"),
-                    TextBlock(t.Message(ItemCount, new { count = 5 })).AutomationId("LocPluralFive"),
+                    TextBlock(t.Message(ItemCount, ("count", 0))).AutomationId("LocPluralZero"),
+                    TextBlock(t.Message(ItemCount, ("count", 5))).AutomationId("LocPluralFive"),
 
                     // Search-results with multiple plural + param
-                    TextBlock(t.Message(SearchResults, new { count = 0, query = locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test" }))
+                    TextBlock(t.Message(SearchResults, ("count", 0), ("query", locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test")))
                         .AutomationId("LocSearchZero"),
-                    TextBlock(t.Message(SearchResults, new { count = 1, query = locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test" }))
+                    TextBlock(t.Message(SearchResults, ("count", 1), ("query", locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test")))
                         .AutomationId("LocSearchOne"),
-                    TextBlock(t.Message(SearchResults, new { count = 42, query = locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test" }))
+                    TextBlock(t.Message(SearchResults, ("count", 42), ("query", locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test")))
                         .AutomationId("LocSearchMany"),
 
                     // Direction label

tests/Reactor.AppTests.Host/SelfTest/Fixtures/LocalizationFixtures.cs

@@ -139,14 +139,14 @@ public override async Task RunAsync()
                     VStack(8,
                         TextBlock(t.Message(AppTitle)).Set(tb => tb.FontSize = 24),
                         TextBlock(t.Message(Welcome)),
-                        TextBlock(t.Message(Greeting, new { name = "World" })),
+                        TextBlock(t.Message(Greeting, ("name", "World"))),
 
-                        TextBlock(t.Message(ItemCount, new { count = 0 })),
-                        TextBlock(t.Message(ItemCount, new { count = 5 })),
+                        TextBlock(t.Message(ItemCount, ("count", 0))),
+                        TextBlock(t.Message(ItemCount, ("count", 5))),
 
-                        TextBlock(t.Message(SearchResults, new { count = 0, query = locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test" })),
-                        TextBlock(t.Message(SearchResults, new { count = 1, query = locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test" })),
-                        TextBlock(t.Message(SearchResults, new { count = 42, query = locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test" })),
+                        TextBlock(t.Message(SearchResults, ("count", 0), ("query", locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test"))),
+                        TextBlock(t.Message(SearchResults, ("count", 1), ("query", locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test"))),
+                        TextBlock(t.Message(SearchResults, ("count", 42), ("query", locale == "ko-KR" ? "\ud14c\uc2a4\ud2b8" : "test"))),
 
                         TextBlock(t.Message(DirectionLabel))
                     )

tests/Reactor.AppTests.Host/SelfTest/SelfTestRunner.cs

@@ -137,18 +137,11 @@ internal static class SelfTestRunner
         // `docs/aot-support.md` showed every remaining failure is a fixture
         // that exercises a subsystem already documented as not-yet-AOT-clean:
         // PropertyGrid auto-discovery, devtools/MCP reflection, UseObservable
-        // on POCOs, anonymous-type localization args, theme resource lookup,
-        // and XAML-metadata-dependent control hosting. Skipping them gives a
-        // 0-failure AOT run that maps cleanly to the documented surface, so a
-        // future fix for any one subsystem (e.g. source-generated PropertyGrid
-        // metadata) translates directly into selftests being re-enabled here.
-
-        // Localization: t.Message(key, new { name = "..." }) reflects on the
-        // anonymous type's properties to build the ICU args dict; properties
-        // get trimmed under AOT. Documented workaround in aot-support.md is
-        // `new Dictionary<string,object> { ["name"] = "..." }`. Whole fixture
-        // is anonymous-type-driven.
-        "Localization_LocaleSwitching",
+        // on POCOs, theme resource lookup, and XAML-metadata-dependent control
+        // hosting. Skipping them gives a 0-failure AOT run that maps cleanly
+        // to the documented surface, so a future fix for any one subsystem
+        // (e.g. source-generated PropertyGrid metadata) translates directly
+        // into selftests being re-enabled here.
 
         // PropertyGrid auto-discovery: ReflectionTypeMetadataProvider walks
         // public properties + builds init-only setters. AOT trims members of

tests/Reactor.Tests/Localization/IntlAccessorTests.cs

@@ -30,7 +30,7 @@ public void Message_WithInterpolation_FormatsArgs()
             .Add("en-US", "Settings", "LoggedInAs", "Logged in as {name}");
 
         var t = CreateAccessor("en-US", provider);
-        var result = t.Message(new MessageKey("Settings", "LoggedInAs"), new { name = "Alice" });
+        var result = t.Message(new MessageKey("Settings", "LoggedInAs"), ("name", "Alice"));
         Assert.Equal("Logged in as Alice", result);
     }
 
@@ -43,9 +43,9 @@ public void Message_IcuPlurals_SelectsCorrectForm()
 
         var t = CreateAccessor("en-US", provider);
 
-        Assert.Equal("Your cart is empty", t.Message(new MessageKey("Cart", "ItemCount"), new { count = 0 }));
-        Assert.Equal("1 item in cart", t.Message(new MessageKey("Cart", "ItemCount"), new { count = 1 }));
-        Assert.Equal("5 items in cart", t.Message(new MessageKey("Cart", "ItemCount"), new { count = 5 }));
+        Assert.Equal("Your cart is empty", t.Message(new MessageKey("Cart", "ItemCount"), ("count", 0)));
+        Assert.Equal("1 item in cart", t.Message(new MessageKey("Cart", "ItemCount"), ("count", 1)));
+        Assert.Equal("5 items in cart", t.Message(new MessageKey("Cart", "ItemCount"), ("count", 5)));
     }
 
     [Fact]
@@ -57,9 +57,9 @@ public void Message_IcuSelect_SelectsCorrectBranch()
 
         var t = CreateAccessor("en-US", provider);
 
-        Assert.Equal("He joined", t.Message(new MessageKey("Profile", "Greeting"), new { gender = "male" }));
-        Assert.Equal("She joined", t.Message(new MessageKey("Profile", "Greeting"), new { gender = "female" }));
-        Assert.Equal("They joined", t.Message(new MessageKey("Profile", "Greeting"), new { gender = "other" }));
+        Assert.Equal("He joined", t.Message(new MessageKey("Profile", "Greeting"), ("gender", "male")));
+        Assert.Equal("She joined", t.Message(new MessageKey("Profile", "Greeting"), ("gender", "female")));
+        Assert.Equal("They joined", t.Message(new MessageKey("Profile", "Greeting"), ("gender", "other")));
     }
 
     [Fact]