feat: support first class function via builtin function

src/builtins.ts

@@ -43,7 +43,8 @@ import {
   NodeKind,
   LiteralExpression,
   ArrayLiteralExpression,
-  IdentifierExpression
+  IdentifierExpression,
+  FunctionExpression
 } from "./ast";
 
 import {
@@ -194,6 +195,8 @@ export namespace BuiltinNames {
   export const instantiate = "~lib/builtins/instantiate";
   export const idof = "~lib/builtins/idof";
 
+  export const experimental_first_class_function = "~lib/builtins/experimental_first_class_function";
+
   export const i8 = "~lib/builtins/i8";
   export const i16 = "~lib/builtins/i16";
   export const i32 = "~lib/builtins/i32";
@@ -3609,6 +3612,26 @@ function builtin_unchecked(ctx: BuiltinFunctionContext): ExpressionRef {
 }
 builtinFunctions.set(BuiltinNames.unchecked, builtin_unchecked);
 
+// experimental_first_class_function(FunctionExpression: *) -> *
+function builtin_experimental_first_class_function(ctx: BuiltinFunctionContext): ExpressionRef {
+  let compiler = ctx.compiler;
+  let module = compiler.module;
+  if (
+    checkTypeAbsent(ctx) |
+    checkArgsRequired(ctx, 1)
+  ) return module.unreachable();
+  let operand = ctx.operands[0];
+  if (operand.kind != NodeKind.Function) {
+    let prototype = ctx.prototype;
+    prototype.program.error(DiagnosticCode._0_expected, operand.range, "FunctionExpression");
+    return module.unreachable();
+  }
+  let functionExpression = <FunctionExpression>operand;
+  let expr = compiler.compileFirstClassFunction(functionExpression);
+  return expr;
+}
+builtinFunctions.set(BuiltinNames.experimental_first_class_function, builtin_experimental_first_class_function);
+
 // call_indirect<T?>(index: u32, ...args: *[]) -> T
 function builtin_call_indirect(ctx: BuiltinFunctionContext): ExpressionRef {
   let compiler = ctx.compiler;
@@ -10668,11 +10691,11 @@ export function compileVisitGlobals(compiler: Compiler): void {
     let global = <Global>element;
     let globalType = global.type;
     let classReference = globalType.getClass();
-    if (
-      classReference &&
-      !classReference.hasDecorator(DecoratorFlags.Unmanaged) &&
-      global.is(CommonFlags.Compiled)
-    ) {
+    let signatureReference = globalType.getSignature();
+    let isGcObject =
+      (classReference != null && !classReference.hasDecorator(DecoratorFlags.Unmanaged)) ||
+      (signatureReference != null && signatureReference.hasEnv);
+    if (isGcObject && global.is(CommonFlags.Compiled)) {
       if (global.is(CommonFlags.Inlined)) {
         let value = global.constantIntegerValue;
         if (i64_low(value) || i64_high(value)) {

src/common.ts

@@ -158,6 +158,7 @@ export namespace CommonNames {
   export const valueof = "valueof";
   export const returnof = "returnof";
   export const nonnull = "nonnull";
+  export const experimental_first_class_function = "experimental_first_class_function";
   // aliases
   export const null_ = "null";
   export const true_ = "true";
@@ -225,6 +226,7 @@ export namespace CommonNames {
   export const Set = "Set";
   export const Map = "Map";
   export const Function = "Function";
+  export const FirstClassFunction = "FirstClassFunctionBase";
   export const ArrayBufferView = "ArrayBufferView";
   export const ArrayBuffer = "ArrayBuffer";
   export const Math = "Math";

src/compiler.ts

@@ -188,7 +188,8 @@ import {
   TypeKind,
   TypeFlags,
   Signature,
-  typesToRefs
+  typesToRefs,
+  SignatureFlags
 } from "./types";
 
 import {
@@ -2054,20 +2055,23 @@ export class Compiler extends DiagnosticEmitter {
 
   // === Table ====================================================================================
 
+  private registerFunctionInTable(instance: Function): u32 {
+    // Add to the function table
+    let functionTable = this.functionTable;
+    let tableBase = this.options.tableBase;
+    if (!tableBase) tableBase = 1; // leave first elem blank
+    let index = tableBase + functionTable.length;
+    functionTable.push(instance);
+    return index;
+  }
+
   /** Ensures that a runtime counterpart of the specified function exists and returns its address. */
   ensureRuntimeFunction(instance: Function): i64 {
     assert(instance.is(CommonFlags.Compiled) && !instance.is(CommonFlags.Stub));
     let program = this.program;
     let memorySegment = instance.memorySegment;
     if (!memorySegment) {
-
-      // Add to the function table
-      let functionTable = this.functionTable;
-      let tableBase = this.options.tableBase;
-      if (!tableBase) tableBase = 1; // leave first elem blank
-      let index = tableBase + functionTable.length;
-      functionTable.push(instance);
-
+      let index = this.registerFunctionInTable(instance);
       // Create runtime function
       let rtInstance = assert(this.resolver.resolveClass(program.functionPrototype, [ instance.type ]));
       let buf = rtInstance.createBuffer();
@@ -6085,12 +6089,13 @@ export class Compiler extends DiagnosticEmitter {
     let functionArg = this.compileExpression(expression.expression, Type.auto);
     let signature = this.currentType.getSignature();
     if (signature) {
+      const thisArg = signature.hasEnv ? functionArg : 0;
       return this.compileCallIndirect(
         signature,
         functionArg,
         expression.args,
         expression,
-        0,
+        thisArg,
         contextualType == Type.void
       );
     }
@@ -7038,6 +7043,38 @@ export class Compiler extends DiagnosticEmitter {
     return module.unreachable();
   }
 
+  compileFirstClassFunction(
+    expression: FunctionExpression
+  ): ExpressionRef {
+    let module = this.module;
+    let flow = this.currentFlow;
+    let sourceFunction = flow.sourceFunction;
+    let declaration = expression.declaration.clone();
+    let anonymousId = sourceFunction.nextAnonymousId++;
+    let contextualTypeArguments = cloneMap(flow.contextualTypeArguments);
+
+    let prototype = new FunctionPrototype(
+      `${sourceFunction.internalName}|anonymous|${anonymousId}`,
+      sourceFunction,
+      declaration
+    );
+    let instance = this.resolver.resolveFirstClassFunction(prototype, contextualTypeArguments, ReportMode.Report);
+    if (!instance) return this.module.unreachable();
+    instance.flow.outer = flow;
+
+    let worked = this.compileFunction(instance);
+    this.currentType = instance.signature.type;
+    if (!worked) return module.unreachable();
+
+    const currentType = this.currentType;
+    if (!instance) return module.unreachable(); 
+    const functionIndexInTable = this.registerFunctionInTable(instance);
+    let ctor = this.ensureConstructor(this.program.firstClassFunctionInstance, expression);
+    let expr = this.makeCallDirect(ctor, [module.i32(0), module.i32(functionIndexInTable), module.usize(0)], expression, /* immediatelyDropped */ false);
+    this.currentType = currentType;
+    return expr;
+  }
+
   private compileFunctionExpression(
     expression: FunctionExpression,
     contextualType: Type,
@@ -8774,7 +8811,7 @@ export class Compiler extends DiagnosticEmitter {
             classInstance.type,
             classInstance.type,
             baseCtor.signature.requiredParameters,
-            baseCtor.signature.hasRest
+            baseCtor.signature.hasRest ? SignatureFlags.Rest : SignatureFlags.None
           ),
           contextualTypeArguments
         );

src/program.ts

@@ -538,6 +538,14 @@ export class Program extends DiagnosticEmitter {
   }
   private _functionPrototype: ClassPrototype | null = null;
 
+  /** Get the first class `Function` instance */
+  get firstClassFunctionInstance(): Class {
+    let cached = this._firstClassFunctionInstance;
+    if (!cached) this._firstClassFunctionInstance = cached = this.requireClass(CommonNames.FirstClassFunction);
+    return cached;
+  }
+  private _firstClassFunctionInstance: Class | null = null;
+
   /** Gets the standard `Int8Array` prototype. */
   get int8ArrayPrototype(): ClassPrototype {
     let cached = this._int8ArrayPrototype;
@@ -1010,6 +1018,12 @@ export class Program extends DiagnosticEmitter {
       this.makeNativeTypeDeclaration(CommonNames.nonnull, CommonFlags.Export | CommonFlags.Generic),
       DecoratorFlags.Builtin
     ));
+    this.nativeFile.add(CommonNames.experimental_first_class_function, new TypeDefinition(
+      CommonNames.experimental_first_class_function,
+      this.nativeFile,
+      this.makeNativeTypeDeclaration(CommonNames.experimental_first_class_function, CommonFlags.Export | CommonFlags.Generic),
+      DecoratorFlags.Builtin
+    ));
 
     // The following types might not be enabled by compiler options, so the
     // compiler needs to check this condition whenever such a value is created
@@ -3741,7 +3755,6 @@ export class FunctionPrototype extends DeclaredElement {
 
 /** A resolved function. */
 export class Function extends TypedElement {
-
   /** Function prototype. */
   prototype: FunctionPrototype;
   /** Function signature. */