Perf #862: promote non-escaping object literals to generated shape structs

Compilation/CompilationContext.Closures.cs

@@ -27,6 +27,13 @@ public partial class CompilationContext
     // `callvirt Invoke` instead of the per-call $TSFunction wrapper + reflective InvokeMethodValue.
     public Dictionary<string, ArrowFunction> DirectCallArrowBindings { get; set; } = [];
 
+    // Generated value-type "shape" structs for promoted object-literal locals (#862). Shared
+    // program-wide (populated by DefineObjectShapeTypes after analysis). EmitVarDeclaration resolves the
+    // struct by canonical shape key for a promoted local; the property get/set fast paths recognise a
+    // promoted local from its slot's CLR type via ByClrType. See TryGetObjectShapeType /
+    // TryGetPromotedObjectLocal.
+    public ObjectShapeRegistry? ObjectShapes { get; set; }
+
     // ============================================
     // Self-referential capture write-back (issue #421)
     // ============================================

Compilation/CompilationContext.cs

@@ -270,6 +270,31 @@ public IReadOnlyList<string> TakePendingLoopLabels()
         return null;
     }
 
+    /// <summary>
+    /// Resolves the generated shape struct for a promoted object-literal local by its canonical shape
+    /// key (#862), or null if shapes are not threaded into this context / the key is unknown. Used at the
+    /// declaration site to pick the struct type to declare the local with.
+    /// </summary>
+    public ObjectShapeTypeInfo? TryGetObjectShapeType(string canonicalKey) =>
+        ObjectShapes?.ByKey.GetValueOrDefault(canonicalKey);
+
+    /// <summary>
+    /// If <paramref name="variableName"/> currently binds to a promoted object-literal local (a slot
+    /// whose CLR type is one of the generated <c>$Shape_N</c> structs, #862), returns its
+    /// <see cref="LocalBuilder"/> and shape info; otherwise null. The slot's CLR type is the single
+    /// source of truth, so this is automatically scope-correct under shadowing and never misfires for a
+    /// captured/object local — no other code path declares a user local with a shape-struct slot.
+    /// </summary>
+    public (LocalBuilder Local, ObjectShapeTypeInfo Shape)? TryGetPromotedObjectLocal(string variableName)
+    {
+        if (ObjectShapes == null) return null;
+        if (!Locals.TryGetLocal(variableName, out var local)) return null;
+        var slotType = Locals.GetLocalType(variableName);
+        if (slotType != null && ObjectShapes.ByClrType.TryGetValue(slotType, out var shape))
+            return (local, shape);
+        return null;
+    }
+
     // Exception block tracking for proper return handling
     public int ExceptionBlockDepth { get; set; } = 0;
     public LocalBuilder? ReturnValueLocal { get; set; }

Compilation/ILCompiler.ArrowFunctions.cs

@@ -1259,6 +1259,7 @@ private void EmitArrowBody(Expr.ArrowFunction arrow, MethodBuilder method, TypeB
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Async.cs

@@ -714,6 +714,7 @@ private void EmitAsyncStateMachineBodies()
                 ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
                 DisplayClasses = _closures.DisplayClasses,
                 DisplayClassFields = _closures.DisplayClassFields,
                 DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -1131,6 +1132,7 @@ private void EmitAsyncMethodBody(MethodBuilder methodBuilder, Stmt.Function meth
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -1364,6 +1366,7 @@ private void EmitTopLevelAsyncArrowBodies()
                 ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
                 DisplayClasses = _closures.DisplayClasses,
                 DisplayClassFields = _closures.DisplayClassFields,
                 DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.AsyncGenerators.cs

@@ -187,6 +187,7 @@ private void EmitAsyncGeneratorMoveNextAsyncBody(AsyncGeneratorStateMachineBuild
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -291,6 +292,7 @@ private void EmitAsyncGeneratorMethodBody(MethodBuilder methodBuilder, Stmt.Func
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Classes.Accessors.cs

@@ -176,6 +176,7 @@ private void EmitAccessorBody(TypeBuilder typeBuilder, Stmt.Accessor accessor, M
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Classes.ClassExpressions.cs

@@ -499,6 +499,7 @@ private CompilationContext CreateClassExpressionContext(
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Classes.Constructors.cs

@@ -51,6 +51,7 @@ private void EmitConstructor(TypeBuilder typeBuilder, Stmt.Class classStmt, Fiel
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Classes.Methods.cs

@@ -928,6 +928,7 @@ private void EmitPrivateMethodBody(
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -1220,6 +1221,7 @@ private void EmitMethod(TypeBuilder typeBuilder, Stmt.Function method, FieldInfo
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Classes.Static.cs

@@ -69,6 +69,7 @@ private void EmitStaticConstructor(TypeBuilder typeBuilder, Stmt.Class classStmt
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -382,6 +383,7 @@ private void EmitStaticMethodBody(string className, Stmt.Function method)
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -625,6 +627,7 @@ private void EmitStaticAsyncMethodBody(string className, Stmt.Function method)
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Functions.cs

@@ -351,6 +351,7 @@ private void EmitFunctionBody(Stmt.Function funcStmt)
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -1007,6 +1008,7 @@ private void EmitDefaultEntryPoint(List<Stmt> statements)
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -1167,6 +1169,7 @@ private void EmitExeEntryPointWithUserMain(List<Stmt> statements, Stmt.Function
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Generators.cs

@@ -403,6 +403,7 @@ private void EmitGeneratorMoveNextBody(GeneratorStateMachineBuilder smBuilder, S
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,
@@ -513,6 +514,7 @@ private void EmitGeneratorMethodBody(MethodBuilder methodBuilder, Stmt.Function
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.InnerFunctions.cs

@@ -449,6 +449,7 @@ private void EmitInnerFunctionBodies()
                 ArrowMethods = _closures.ArrowMethods,
                 ConstArrowBindings = _closures.ConstArrowBindings,
                 DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+                ObjectShapes = _closures.ObjectShapes,
                 DisplayClasses = _closures.DisplayClasses,
                 DisplayClassFields = _closures.DisplayClassFields,
                 DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.Modules.cs

@@ -705,6 +705,7 @@ private CompilationContext CreateCompilationContext(ILGenerator il)
             ArrowMethods = _closures.ArrowMethods,
             ConstArrowBindings = _closures.ConstArrowBindings,
             DirectCallArrowBindings = _closures.DirectCallArrowBindings,
+            ObjectShapes = _closures.ObjectShapes,
             DisplayClasses = _closures.DisplayClasses,
             DisplayClassFields = _closures.DisplayClassFields,
             DisplayClassConstructors = _closures.DisplayClassConstructors,

Compilation/ILCompiler.State.cs

@@ -138,6 +138,11 @@ private sealed class ClosureCompilationState
         // NonEscapingArrowLocalAnalyzer; the fast path only fires for capturing arrows whose in-scope
         // local slot type matches the display class (so a same-named binding elsewhere never hits it).
         public Dictionary<string, Expr.ArrowFunction> DirectCallArrowBindings { get; } = [];
+
+        // Generated value-type "shape" structs for promoted object-literal locals (#862). Populated
+        // after ObjectLocalPromotionAnalyzer by DefineObjectShapeTypes; the declaration site keys in by
+        // canonical shape key, and the property get/set fast paths key in by the local slot's CLR type.
+        public ObjectShapeRegistry ObjectShapes { get; } = new();
         public Dictionary<Expr.ArrowFunction, TypeBuilder> DisplayClasses { get; } = new(ReferenceEqualityComparer.Instance);
         public Dictionary<Expr.ArrowFunction, Dictionary<string, FieldBuilder>> DisplayClassFields { get; } = new(ReferenceEqualityComparer.Instance);
         public Dictionary<Expr.ArrowFunction, ConstructorBuilder> DisplayClassConstructors { get; } = new(ReferenceEqualityComparer.Instance);

Compilation/ILCompiler.cs

@@ -426,7 +426,9 @@ public void Compile(List<Stmt> statements, TypeMap typeMap, DeadCodeInfo? deadCo
         Phase2_AnalyzeClosures(statements);
         ArrayLocalPromotionAnalyzer.Analyze(statements, _typeMap, _closures.Analyzer);
         NonEscapingArrowLocalAnalyzer.Analyze(statements, _closures.DirectCallArrowBindings, _closures.Analyzer);
+        ObjectLocalPromotionAnalyzer.Analyze(statements, _typeMap, _closures.Analyzer);
         Phase3_CreateProgramType();
+        DefineObjectShapeTypes();
         PreScanBuiltInModuleImports(statements);
         Phase4_DefineDeclarations(statements);
         Phase5_CollectArrowFunctions(statements);
@@ -705,13 +707,59 @@ private void Phase8_EmitEntryPoint(List<Stmt> statements)
         EmitEntryPoint(statements);
     }
 
+    /// <summary>
+    /// Defines one generated value-type <c>$Shape_N</c> struct per distinct promotable object-literal
+    /// shape (#862), de-duplicated by canonical key. Each field becomes a typed public field
+    /// (<c>number</c>→<c>double</c>, <c>boolean</c>→<c>bool</c>, <c>string</c>→<c>string</c>). The structs
+    /// reference only BCL types, so compiled output stays standalone (no SharpTS.dll dependency). They are
+    /// finalized (<c>CreateType</c>) at the top of the finalize phase, before any type that uses them.
+    /// </summary>
+    private void DefineObjectShapeTypes()
+    {
+        if (_typeMap == null) return;
+        foreach (var shape in _typeMap.PromotableObjectLocalShapes)
+        {
+            if (_closures.ObjectShapes.ByKey.ContainsKey(shape.CanonicalKey)) continue;
+
+            var structType = _moduleBuilder.DefineType(
+                $"$Shape_{_closures.ObjectShapes.Counter++}",
+                TypeAttributes.Public | TypeAttributes.Sealed | TypeAttributes.SequentialLayout,
+                _types.ValueType);
+
+            var fieldBuilders = new Dictionary<string, FieldBuilder>(StringComparer.Ordinal);
+            foreach (var (name, kind) in shape.Fields)
+            {
+                var clr = kind switch
+                {
+                    TokenType.TYPE_NUMBER => _types.Double,
+                    TokenType.TYPE_BOOLEAN => _types.Boolean,
+                    _ => _types.String,
+                };
+                fieldBuilders[name] = structType.DefineField(name, clr, FieldAttributes.Public);
+            }
+
+            var info = new ObjectShapeTypeInfo
+            {
+                ClrType = structType,
+                Fields = shape.Fields.Select(f => (f.Name, f.Kind)).ToList(),
+                FieldBuilders = fieldBuilders,
+            };
+            _closures.ObjectShapes.ByKey[shape.CanonicalKey] = info;
+            _closures.ObjectShapes.ByClrType[structType] = info;
+        }
+    }
+
     /// <summary>
     /// Phase 9: Finalize all types by calling CreateType().
     /// </summary>
     private void Phase9_FinalizeTypes()
     {
         _unionGenerator?.FinalizeAllUnionTypes();
 
+        // Finalize generated object-literal shape structs (#862) before any type that uses them.
+        foreach (var info in _closures.ObjectShapes.ByKey.Values)
+            ((TypeBuilder)info.ClrType).CreateType();
+
         // Finalize entry-point display class first (needed by closures)
         _closures.EntryPointDisplayClass?.CreateType();
 
@@ -908,7 +956,9 @@ public void CompileModules(List<ParsedModule> modules, ModuleResolver resolver,
         Phase2_AnalyzeClosures(allStatements);
         ArrayLocalPromotionAnalyzer.Analyze(allStatements, _typeMap, _closures.Analyzer);
         NonEscapingArrowLocalAnalyzer.Analyze(allStatements, _closures.DirectCallArrowBindings, _closures.Analyzer);
+        ObjectLocalPromotionAnalyzer.Analyze(allStatements, _typeMap, _closures.Analyzer);
         Phase3_CreateProgramType();
+        DefineObjectShapeTypes();
         // Scope each module's named-import bindings to that module so local
         // aliases like __platform don't collide between stdlib modules.
         foreach (var m in modules)
@@ -1167,6 +1217,10 @@ private void ModulePhase11_FinalizeTypes()
 
         _unionGenerator?.FinalizeAllUnionTypes();
 
+        // Finalize generated object-literal shape structs (#862) before any type that uses them.
+        foreach (var info in _closures.ObjectShapes.ByKey.Values)
+            ((TypeBuilder)info.ClrType).CreateType();
+
         // Finalize entry-point display class first (needed by closures)
         _closures.EntryPointDisplayClass?.CreateType();