Strict tsconfig; more major steps toward ocap style

packages/core/examples/box-and-client.js

@@ -30,7 +30,7 @@ console.time('box-and-client-' + N.toString());
 
 export function boot(thisFacet) {
   thisFacet.spawn('box', function (thisFacet) {
-    thisFacet.actor.dataspace.declareField(this, 'value', 0);
+    thisFacet.declareField(this, 'value', 0);
     thisFacet.addEndpoint(() => {
       // console.log('recomputing published BoxState', this.value);
       return { assertion: BoxState(this.value), analysis: null };

packages/core/src/compiler/grammar.ts

@@ -1,5 +1,5 @@
 import {
-    Item, Items,
+    Token, Items,
     Pattern,
 
     scope, bind, seq, alt, upTo, atom, group, exec,
@@ -11,7 +11,7 @@ import * as Matcher from '../syntax/matcher.js';
 
 export type Expr = Items;
 export type Statement = Items;
-export type Identifier = Item;
+export type Identifier = Token;
 
 export const block = (acc?: Items) =>
     (acc === void 0)
@@ -21,15 +21,6 @@ export const block = (acc?: Items) =>
 export const statementBoundary = alt(atom(';'), Matcher.newline, Matcher.end);
 export const exprBoundary = alt(atom(';'), atom(','), group('{', discard), Matcher.end);
 
-export interface SpawnStatement {
-    isDataspace: boolean;
-    name?: Expr;
-    initialAssertions: Expr[];
-    parentIds: Identifier[];
-    parentInits: Expr[];
-    bootProcBody: Statement;
-}
-
 export const identifier: Pattern<Identifier> = atom();
 
 export function expr(... extraStops: Pattern<any>[]): Pattern<Expr> {
@@ -42,8 +33,34 @@ export function statement(acc: Items): Pattern<void> {
                                 map(statementBoundary, i => i ? acc.push(i) : void 0))));
 }
 
+export interface FacetAction {
+    implicitFacet: boolean;
+}
+
+export function facetAction<I extends FacetAction, T extends I>(
+    pattern: (scope: T) => Pattern<any>): Pattern<T>
+{
+    return i => {
+        const scope = Object.create(null);
+        scope.implicitFacet = true;
+        const p = seq(option(map(atom('.'), _ => scope.implicitFacet = false)), pattern(scope));
+        const r = p(i);
+        if (r === null) return null;
+        return [scope, r[1]];
+    };
+}
+
+export interface SpawnStatement extends FacetAction {
+    isDataspace: boolean;
+    name?: Expr;
+    initialAssertions: Expr[];
+    parentIds: Identifier[];
+    parentInits: Expr[];
+    bootProcBody: Statement;
+}
+
 export const spawn: Pattern<SpawnStatement> & { headerExpr: Pattern<Expr> } =
-    Object.assign(scope((o: SpawnStatement) => {
+    Object.assign(facetAction((o: SpawnStatement) => {
         o.isDataspace = false;
         o.initialAssertions = [];
         o.parentIds = [];
@@ -69,38 +86,50 @@ export const spawn: Pattern<SpawnStatement> & { headerExpr: Pattern<Expr> } =
         headerExpr: expr(atom(':asserting'), atom(':let')),
     });
 
-export interface FieldDeclarationStatement {
+export interface FieldDeclarationStatement extends FacetAction {
     member: Expr;
     expr?: Expr;
 }
 
+// Principal: Dataspace, but only for implementation reasons, so really Facet
 export const fieldDeclarationStatement: Pattern<FieldDeclarationStatement> =
-    scope(o => seq(atom('field'),
-                   bind(o, 'member', expr(atom('='))),
-                   option(seq(atom('='), bind(o, 'expr', expr())))));
+    facetAction(o => seq(atom('field'),
+                         bind(o, 'member', expr(atom('='))),
+                         option(seq(atom('='), bind(o, 'expr', expr()))),
+                         statementBoundary));
 
-export interface AssertionEndpointStatement {
+export interface AssertionEndpointStatement extends FacetAction {
     isDynamic: boolean,
     template: Expr,
     test?: Expr,
 }
 
+// Principal: Facet
 export const assertionEndpointStatement: Pattern<AssertionEndpointStatement> =
-    scope(o => {
+    facetAction(o => {
         o.isDynamic = true;
         return seq(atom('assert'),
                    option(map(atom(':snapshot'), _ => o.isDynamic = false)),
                    bind(o, 'template', expr(seq(atom('when'), group('(', discard)))),
-                   option(seq(atom('when'), group('(', bind(o, 'test', expr())))));
+                   option(seq(atom('when'), group('(', bind(o, 'test', expr())))),
+                   statementBoundary);
     });
 
-export const dataflowStatement: Pattern<Statement> =
-    value(o => {
-        o.value = [];
-        return seq(atom('dataflow'), statement(o.value));
+export interface StatementFacetAction extends FacetAction {
+    body: Statement;
+}
+
+export function statementFacetAction(kw: Pattern<any>): Pattern<StatementFacetAction> {
+    return facetAction(o => {
+        o.body = [];
+        return seq(kw, statement(o.body));
     });
+}
+
+// Principal: Facet
+export const dataflowStatement = statementFacetAction(atom('dataflow'));
 
-export interface EventHandlerEndpointStatement {
+export interface EventHandlerEndpointStatement extends FacetAction {
     terminal: boolean;
     triggerType: 'dataflow' | 'start' | 'stop' | 'asserted' | 'retracted' | 'message';
     isDynamic: boolean;
@@ -108,8 +137,9 @@ export interface EventHandlerEndpointStatement {
     body: Statement;
 }
 
+// Principal: Facet
 export const eventHandlerEndpointStatement: Pattern<EventHandlerEndpointStatement> =
-    scope(o => {
+    facetAction(o => {
         o.terminal = false;
         o.isDynamic = true;
         o.body = [];
@@ -125,8 +155,9 @@ export const eventHandlerEndpointStatement: Pattern<EventHandlerEndpointStatemen
                                         atom('message')),
                                     e => e.text)),
                            option(map(atom(':snapshot'), _ => o.isDynamic = false)),
-                           bind(o, 'pattern', expr()),
-                           option(statement(o.body)))));
+                           bind(o, 'pattern', expr(atom('=>'))),
+                           alt(seq(atom('=>'), statement(o.body)),
+                               statementBoundary))));
     });
 
 export interface TypeDefinitionStatement {
@@ -136,6 +167,7 @@ export interface TypeDefinitionStatement {
     wireName?: Expr;
 }
 
+// Principal: none
 export const typeDefinitionStatement: Pattern<TypeDefinitionStatement> =
     scope(o => seq(bind(o, 'expectedUse', map(alt(atom('message'), atom('assertion')), e => e.text)),
                    atom('type'),
@@ -145,24 +177,39 @@ export const typeDefinitionStatement: Pattern<TypeDefinitionStatement> =
                               bind(o, 'wireName', withoutSpace(upTo(statementBoundary))))),
                    statementBoundary));
 
-export const messageSendStatement: Pattern<Expr> =
-    value(o => seq(atom('send'), bind(o, 'value', withoutSpace(upTo(statementBoundary))), statementBoundary));
+export interface MessageSendStatement extends FacetAction {
+    expr: Expr;
+}
+
+// Principal: Facet
+export const messageSendStatement: Pattern<MessageSendStatement> =
+    facetAction(o => seq(atom('send'),
+                         bind(o, 'expr', withoutSpace(upTo(statementBoundary))),
+                         statementBoundary));
 
-export interface DuringStatement {
+export interface DuringStatement extends FacetAction {
     pattern: Expr;
     body: Statement;
 }
 
+// Principal: Facet
 export const duringStatement: Pattern<DuringStatement> =
-    scope(o => {
+    facetAction(o => {
         o.body = [];
         return seq(atom('during'),
                    bind(o, 'pattern', expr()),
                    statement(o.body));
     });
 
-export const reactStatement: Pattern<Statement> =
+// Principal: Facet
+export const reactStatement = statementFacetAction(atom('react'));
+
+// Principal: none
+export const bootStatement: Pattern<Statement> =
     value(o => {
         o.value = [];
-        return seq(atom('react'), statement(o.value));
+        return seq(atom('boot'), statement(o.value));
     });
+
+// Principal: Facet
+export const stopStatement = statementFacetAction(atom('stop'));

packages/core/src/compiler/internals.ts

@@ -0,0 +1 @@
+export const BootProc = '__SYNDICATE__bootProc';

packages/core/src/compiler/main.ts

@@ -1,6 +1,8 @@
 import fs from 'fs';
 import * as S from '../syntax/index.js';
+import { ArrayList, Substitution } from '../syntax/index.js';
 import * as G from './grammar.js';
+import { BootProc } from './internals.js';
 
 export function main(argv: string[]) {
     let [ inputFilename ] = argv.slice(2);
@@ -12,6 +14,8 @@ export function main(argv: string[]) {
     let tree = reader.readToEnd();
     let macro = new S.Templates();
 
+    tree = macro.template()`import * as __SYNDICATE__ from '@syndicate/core';\n${tree}`;
+
     let passNumber = 1;
     let expansionNeeded = true;
     function expand<T>(p: S.Pattern<T>, f: (t: T) => S.Items) {
@@ -20,29 +24,90 @@ export function main(argv: string[]) {
             return f(t);
         });
     }
+
+    function receiverFor(s: G.FacetAction): Substitution {
+        return (s.implicitFacet) ? 'thisFacet.' : '.';
+    }
+
+    function expandFacetAction<T extends G.FacetAction>(p: S.Pattern<T>, f: (t: T) => S.Items) {
+        expand(p, t => macro.template()`${receiverFor(t)}${f(t)}`);
+    }
+
     while (expansionNeeded) {
         if (passNumber >= 128) {
             throw new Error(`Too many compiler passes (${passNumber})!`);
         }
         expansionNeeded = false;
-        expand(G.spawn,
-               s => macro.template()`SPAWN[${s.name ?? []}][${S.joinItems(s.initialAssertions, ', ')}][[${s.bootProcBody}]]`);
-        expand(G.fieldDeclarationStatement,
-               s => macro.template()`FIELD[${s.member}][${s.expr ?? []}]`);
-        expand(G.assertionEndpointStatement,
-               s => macro.template()`ASSERT[${''+s.isDynamic}][${s.template}][${s.test ?? []}]`);
-        expand(G.dataflowStatement,
-               e => macro.template()`DATAFLOW[${e}]`);
-        expand(G.eventHandlerEndpointStatement,
-               s => macro.template()`EVENTHANDLER[${`${s.terminal}/${s.isDynamic}`}][${s.triggerType}][${s.pattern}][${s.body}]`);
-        expand(G.typeDefinitionStatement,
-               s => macro.template()`TYPEDEF[${s.expectedUse}][${[s.label]}][${S.joinItems(s.fields.map(f => [f]), ' -- ')}][${s.wireName ?? []}]`);
-        expand(G.messageSendStatement,
-               e => macro.template()`SEND[${e}]`);
-        expand(G.duringStatement,
-               s => macro.template()`DURING[${s.pattern}][${s.body}]`);
-        expand(G.reactStatement,
-               e => macro.template()`REACT[${e}]`);
+        expandFacetAction(
+            G.spawn,
+            s => {
+                let proc = macro.template()`function (thisFacet) {${s.bootProcBody}}`;
+                if (s.isDataspace) proc = macro.template()`__SYNDICATE__.inNestedDataspace(${proc})`;
+                let assertions = (s.initialAssertions.length > 0)
+                    ? macro.template()`, new __SYNDICATE__.Set([${S.joinItems(s.initialAssertions, ', ')}])`
+                    : ``;
+                return macro.template()`_spawn(${s.name ?? 'null'}, ${proc}${assertions});`;
+            });
+        expandFacetAction(
+            G.fieldDeclarationStatement,
+            s => {
+                function isArrayProp(): [S.Substitution, S.Substitution] | null {
+                    if (s.member.length === 0) return null;
+                    const x = s.member[s.member.length - 1];
+                    if (!S.isGroup(x)) return null;
+                    if (x.start.text !== '[') return null;
+                    return [s.member.slice(0, s.member.length - 1), x.items];
+                }
+                function isSimpleProp(): [S.Substitution, S.Substitution] | null {
+                    if (s.member.length < 2) return null;
+                    const r = S.value<G.Identifier>(o => S.seq(S.atom('.'), S.bind(o, 'value', G.identifier)))(
+                        new ArrayList(s.member, s.member.length - 2));
+                    if (r === null) return null;
+                    const id = r[0];
+                    return [s.member.slice(0, s.member.length - 2),
+                            [ { start: id.start,
+                                end: id.end,
+                                type: S.TokenType.STRING,
+                                text: JSON.stringify(id.text) } ]];
+                }
+                const [obj, prop] = isArrayProp()
+                    ?? isSimpleProp()
+                    ?? ["__SYNDICATE__.INVALID_PROPERTY_SYNTAX", "''"];
+                return macro.template()`declareField(${obj}, ${prop}, ${s.expr ?? 'void 0'});`;
+            });
+        expandFacetAction(
+            G.assertionEndpointStatement,
+            s => macro.template()`addEndpoint(thisFacet => (${s.test ?? 'true'}) && (${s.template}), ${''+s.isDynamic});`);
+        expandFacetAction(
+            G.dataflowStatement,
+            s => macro.template()`addDataflow(function (thisFacet) {${s.body}});`);
+        expandFacetAction(
+            G.eventHandlerEndpointStatement,
+            s => {
+                return macro.template()`EVENTHANDLER[${`${s.terminal}/${s.isDynamic}`}][${s.triggerType}][${s.pattern ?? []}][${s.body}]`;
+            });
+        expandFacetAction(
+            G.duringStatement,
+            s => macro.template()`DURING[${s.pattern}][${s.body}]`);
+        expand(
+            G.typeDefinitionStatement,
+            s => {
+                const l = JSON.stringify(s.label.text);
+                const fs = JSON.stringify(s.fields.map(f => f.text));
+                return macro.template()`const ${[s.label]} = __SYNDICATE__.Record.makeConstructor(${s.wireName ?? l}, ${fs});`;
+            });
+        expandFacetAction(
+            G.messageSendStatement,
+            s => macro.template()`_send(${s.expr});`);
+        expandFacetAction(
+            G.reactStatement,
+            s => macro.template()`addChildFacet(function (thisFacet) {${s.body}});`);
+        expand(
+            G.bootStatement,
+            s => macro.template()`export function ${BootProc}(thisFacet) {${s}}`);
+        expandFacetAction(
+            G.stopStatement,
+            s => macro.template()`_stop(function (thisFacet) {${s.body}});`);
     }
 
     console.log(S.itemText(tree, { color: true, missing: '\x1b[41m□\x1b[0m' }));

packages/core/src/runtime/dataflow.ts

@@ -101,10 +101,11 @@ export class Graph<SubjectId, ObjectId> {
         }
     }
 
-    defineObservableProperty(obj: object,
-                             prop: string,
-                             value: any,
-                             options: PropertyOptions<ObjectId>)
+    defineObservableProperty<T, K extends keyof T>(
+        obj: T,
+        prop: K,
+        value: T[K],
+        options: PropertyOptions<ObjectId>)
     {
         const { objectId, noopGuard } = options;
         Object.defineProperty(obj, prop, {
@@ -125,9 +126,10 @@ export class Graph<SubjectId, ObjectId> {
         return objectId;
     }
 
-    static newScope(o: object): object {
-        function O() {}
-        O.prototype = o;
-        return new O();
+    static newScope<T, R extends T>(o: T): R {
+        const Scope: { new (): R, prototype: T } =
+            (function Scope () {}) as unknown as ({ new (): R, prototype: T });
+        Scope.prototype = o;
+        return new Scope();
     }
 }

packages/core/src/runtime/dataspace.ts

@@ -82,18 +82,6 @@ export abstract class Dataspace {
         this.pendingTurns = [new Turn(null, [new Spawn(null, bootProc, new Set())])];
     }
 
-    _inScript = true;
-
-    withNonScriptContext<T>(task: Task<T>): T {
-        let savedInScript = this._inScript;
-        this._inScript = false;
-        try {
-            return task();
-        } finally {
-            this._inScript = savedInScript;
-        }
-    }
-
     abstract start(): this;
     abstract ground(): Ground;
 
@@ -101,29 +89,6 @@ export abstract class Dataspace {
         return this.ground().backgroundTask();
     }
 
-    referenceField(obj: DataflowObservableObject, prop: string) {
-        if (!(prop in obj)) {
-            this.dataflow.recordObservation([obj, prop]);
-        }
-        return obj[prop];
-    }
-
-    declareField(obj: DataflowObservableObject, prop: string, init: any) {
-        if (prop in obj) {
-            obj[prop] = init;
-        } else {
-            this.dataflow.defineObservableProperty(obj, prop, init, {
-                objectId: [obj, prop],
-                noopGuard: is
-            });
-        }
-    }
-
-    deleteField(obj: DataflowObservableObject, prop: string) {
-        this.dataflow.recordDamage([obj, prop]);
-        delete obj[prop];
-    }
-
     runTasks() { // TODO: rename?
         this.runPendingTasks();
         this.performPendingActions();
@@ -153,17 +118,15 @@ export abstract class Dataspace {
     }
 
     refreshAssertions() {
-        this.withNonScriptContext(() => {
-            this.dataflow.repairDamage((ep) => {
-                let facet = ep.facet;
-                if (facet.isLive) { // TODO: necessary test, or tautological?
-                    facet.invokeScript(() => ep.refresh());
-                }
-            });
+        this.dataflow.repairDamage((ep) => {
+            let facet = ep.facet;
+            if (facet.isLive) { // TODO: necessary test, or tautological?
+                facet.invokeScript(f => f.withNonScriptContext(() => ep.refresh()));
+            }
         });
     }
 
-    addActor(name: any, bootProc: Script<void>, initialAssertions: Set, parentActor: Actor | undefined) {
+    addActor(name: any, bootProc: Script<void>, initialAssertions: Set, parentActor: Actor | null) {
         let ac = new Actor(this, name, initialAssertions, parentActor?.id);
         // debug('Spawn', ac && ac.toString());
         this.applyPatch(ac, ac.adhocAssertions);
@@ -178,7 +141,7 @@ export abstract class Dataspace {
 
     applyPatch(ac: Actor, delta: Bag) {
         // if (!delta.isEmpty()) debug('applyPatch BEGIN', ac && ac.toString());
-        let removals = [];
+        let removals: Array<[number, Value]> = [];
         delta.forEach((count, a) => {
             if (count > 0) {
                 // debug('applyPatch +', a && a.toString());
@@ -195,7 +158,7 @@ export abstract class Dataspace {
         // if (!delta.isEmpty()) debug('applyPatch END');
     }
 
-    deliverMessage(m: Value, _sendingActor: Actor) {
+    deliverMessage(m: Value, _sendingActor: Actor | null) {
         // debug('deliverMessage', sendingActor && sendingActor.toString(), m.toString());
         this.index.deliverMessage(m);
         // this.index.deliverMessage(m, (leaf, _m) => {
@@ -208,11 +171,11 @@ export abstract class Dataspace {
     }
 
     subscribe(handler: Skeleton.Analysis) {
-        this.index.addHandler(handler, handler.callback);
+        this.index.addHandler(handler, handler.callback!);
     }
 
     unsubscribe(handler: Skeleton.Analysis) {
-        this.index.removeHandler(handler, handler.callback);
+        this.index.removeHandler(handler, handler.callback!);
     }
 
     endpointHook(_facet: Facet, _endpoint: Endpoint) {
@@ -269,7 +232,7 @@ export class Actor {
         let tasks = this.pendingTasks;
         for (let i = 0; i < Priority._count; i++) {
             let q = tasks[i];
-            if (q.length > 0) return q.shift();
+            if (q.length > 0) return q.shift()!;
         }
         return null;
     }
@@ -287,12 +250,12 @@ export class Actor {
         this.pendingTasks[priority].push(task);
     }
 
-    addFacet(parentFacet: Facet, bootProc: Script<void>, checkInScript: boolean = false) {
-        if (checkInScript && !this.dataspace._inScript) {
+    addFacet(parentFacet: Facet | null, bootProc: Script<void>, checkInScript: boolean = false) {
+        if (checkInScript && parentFacet && !parentFacet.inScript) {
             throw new Error("Cannot add facet outside script; are you missing a `react { ... }`?");
         }
         let f = new Facet(this, parentFacet);
-        f.invokeScript(f => this.dataspace.withNonScriptContext(() => bootProc.call(f.fields, f)));
+        f.invokeScript(f => f.withNonScriptContext(() => bootProc.call(f.fields, f)));
         this.scheduleTask(() => {
             if ((parentFacet && !parentFacet.isLive) || f.isInert()) {
                 f._terminate();
@@ -352,7 +315,7 @@ export class Actor {
 }
 
 abstract class Action {
-    abstract perform(ds: Dataspace, ac: Actor): void;
+    abstract perform(ds: Dataspace, ac: Actor | null): void;
 }
 
 class Patch extends Action {
@@ -363,8 +326,8 @@ class Patch extends Action {
         this.changes = changes;
     }
 
-    perform(ds: Dataspace, ac: Actor): void {
-        ds.applyPatch(ac, this.changes);
+    perform(ds: Dataspace, ac: Actor | null): void {
+        ds.applyPatch(ac!, this.changes);
     }
 
     adjust(a: Value, count: number) {
@@ -380,7 +343,7 @@ class Message extends Action {
         this.body = fromJS(body);
     }
 
-    perform(ds: Dataspace, ac: Actor): void {
+    perform(ds: Dataspace, ac: Actor | null): void {
         ds.deliverMessage(this.body, ac);
     }
 }
@@ -397,7 +360,7 @@ class Spawn extends Action {
         this.initialAssertions = initialAssertions;
     }
 
-    perform(ds: Dataspace, ac: Actor): void {
+    perform(ds: Dataspace, ac: Actor | null): void {
         ds.addActor(this.name, this.bootProc, this.initialAssertions, ac);
     }
 }
@@ -405,7 +368,8 @@ class Spawn extends Action {
 class Quit extends Action { // TODO: rename? Perhaps to Cleanup?
     // Pseudo-action - not for userland use.
 
-    perform(ds: Dataspace, ac: Actor): void {
+    perform(ds: Dataspace, ac: Actor | null): void {
+        if (ac === null) throw new Error("Internal error: Quit action with null actor");
         ds.applyPatch(ac, ac.cleanupChanges);
         ds.actors.delete(ac.id);
         // debug('Quit', ac && ac.toString());
@@ -420,9 +384,9 @@ class DeferredTurn extends Action {
         this.continuation = continuation;
     }
 
-    perform(_ds: Dataspace, ac: Actor): void {
+    perform(_ds: Dataspace, ac: Actor | null): void {
         // debug('DeferredTurn', ac && ac.toString());
-        ac.scheduleTask(this.continuation);
+        ac!.scheduleTask(this.continuation);
     }
 }
 
@@ -449,6 +413,7 @@ export class Facet {
     readonly stopScripts: Array<Script<void>> = [];
     readonly children = new IdentitySet<Facet>();
     readonly fields: any;
+    inScript = true;
 
     constructor(actor: Actor, parent: Facet | null) {
         this.id = actor.dataspace.nextId++;
@@ -467,6 +432,16 @@ export class Facet {
         this.fields[DataflowObservableObjectId] = () => this.id;
     }
 
+    withNonScriptContext<T>(task: Task<T>): T {
+        let savedInScript = this.inScript;
+        this.inScript = false;
+        try {
+            return task();
+        } finally {
+            this.inScript = savedInScript;
+        }
+    }
+
     _abort(emitPatches: boolean) {
         this.isLive = false;
         this.children.forEach(child => child._abort(emitPatches));
@@ -517,12 +492,17 @@ export class Facet {
         }, Priority.GC);
     }
 
+    // This alias exists because of the naive expansion done by the parser.
+    _stop(continuation?: Script<void>) {
+        this.stop(continuation);
+    }
+
     stop(continuation?: Script<void>) {
-        this.parent.invokeScript(() => {
+        this.parent!.invokeScript(() => {
             this.actor.scheduleTask(() => {
                 this._terminate();
                 if (continuation) {
-                    this.parent.scheduleScript(parent => continuation.call(this.fields, parent));
+                    this.parent!.scheduleScript(parent => continuation.call(this.fields, parent));
                     // ^ TODO: is this the correct scope to use??
                 }
             });
@@ -539,7 +519,7 @@ export class Facet {
         this.stopScripts.push(s);
     }
 
-    addEndpoint(updateFun: () => EndpointSpec, isDynamic: boolean = true): Endpoint {
+    addEndpoint(updateFun: Script<EndpointSpec>, isDynamic: boolean = true): Endpoint {
         const ep = new Endpoint(this, isDynamic, updateFun);
         this.actor.dataspace.endpointHook(this, ep);
         return ep;
@@ -582,7 +562,7 @@ export class Facet {
             this.scheduleScript(() => {
                 if (this.isLive) {
                     this.actor.dataspace.dataflow.withSubject(subjectId, () =>
-                        subjectFun.call(this.fields));
+                        subjectFun.call(this.fields, this));
                 }
             }, priority);
             return { assertion: void 0, analysis: null };
@@ -624,7 +604,7 @@ export class Facet {
     }
 
     wrap<T extends Array<any>, R>(fn: (f: Facet, ... args: T) => R): (... args: T) => R {
-        return (... actuals) => this.invokeScript(f => fn.call(f.fields, f, ... actuals), true);
+        return (... actuals) => this.invokeScript(f => fn.call(f.fields, f, ... actuals), true)!;
     }
 
     wrapExternal<T extends Array<any>>(fn: (f: Facet, ... args: T) => void): (... args: T) => void {
@@ -638,22 +618,32 @@ export class Facet {
     }
 
     ensureFacetSetup(what: string) {
-        if (this.actor.dataspace._inScript) {
+        if (this.inScript) {
             throw new Error(`Cannot ${what} outside facet setup; are you missing \`react { ... }\`?`);
         }
     }
 
     ensureNonFacetSetup(what: string, keyword: string) {
-        if (!this.actor.dataspace._inScript) {
+        if (!this.inScript) {
             throw new Error(`Cannot ${what} during facet setup; are you missing \`${keyword} { ... }\`?`);
         }
     }
 
+    // This alias exists because of the naive expansion done by the parser.
+    _send(body: any) {
+        this.send(body);
+    }
+
     send(body: any) {
         this.ensureNonFacetSetup('`send`', 'on start');
         this.enqueueScriptAction(new Message(body));
     }
 
+    // This alias exists because of the naive expansion done by the parser.
+    _spawn(name: any, bootProc: Script<void>, initialAssertions?: Set) {
+        this.spawn(name, bootProc, initialAssertions);
+    }
+
     spawn(name: any, bootProc: Script<void>, initialAssertions?: Set) {
         this.ensureNonFacetSetup('`spawn`', 'on start');
         this.enqueueScriptAction(new Spawn(name, bootProc, initialAssertions));
@@ -667,6 +657,33 @@ export class Facet {
     scheduleScript(script: Script<void>, priority?: Priority) {
         this.actor.scheduleTask(this.wrap(script), priority);
     }
+
+    declareField<T extends DataflowObservableObject, K extends keyof T & string>(obj: T, prop: K, init: T[K]) {
+        if (prop in obj) {
+            obj[prop] = init;
+        } else {
+            this.actor.dataspace.dataflow.defineObservableProperty(obj, prop, init, {
+                objectId: [obj, prop],
+                noopGuard: is
+            });
+        }
+    }
+
+    // referenceField(obj: DataflowObservableObject, prop: string) {
+    //     if (!(prop in obj)) {
+    //         this.actor.dataspace.dataflow.recordObservation([obj, prop]);
+    //     }
+    //     return obj[prop];
+    // }
+
+    // deleteField(obj: DataflowObservableObject, prop: string) {
+    //     this.actor.dataspace.dataflow.recordDamage([obj, prop]);
+    //     delete obj[prop];
+    // }
+
+    addChildFacet(bootProc: Script<void>) {
+        this.actor.addFacet(this, bootProc, true);
+    }
 }
 
 export class Endpoint {
@@ -685,6 +702,7 @@ export class Endpoint {
         let initialSpec = ds.dataflow.withSubject(isDynamic ? this : undefined,
                                                   () => updateFun.call(facet.fields, facet));
         this._install(initialSpec);
+        this.spec = initialSpec; // keeps TypeScript's undefinedness-checker happy
         facet.endpoints.set(this.id, this);
     }
 

packages/core/src/runtime/randomid.ts

@@ -38,6 +38,6 @@ export function randomId(byteCount: number, hexOutput: boolean = false): string
     if (hexOutput) {
         return Bytes.from(buf).toHex();
     } else {
-        return _btoa(String.fromCharCode.apply(null, buf)).replace(/=/g,'');
+        return _btoa(String.fromCharCode.apply(null, buf as unknown as number[])).replace(/=/g,'');
     }
 }

packages/core/src/runtime/relay.ts

@@ -16,7 +16,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 //---------------------------------------------------------------------------
 
-import { Value } from 'preserves';
+import { Value, Record } from 'preserves';
 
 import { $Special } from './special.js';
 import { Dataspace, Facet, Actor, Endpoint, Script } from './dataspace.js';
@@ -43,44 +43,47 @@ export class NestedDataspace extends Dataspace {
     }
 
     endpointHook(facet: Facet, innerEp: Endpoint) {
-        const innerDs = this;
         super.endpointHook(facet, innerEp);
-        if (Observe.isClassOf(innerEp.spec.assertion) &&
-            Inbound.isClassOf(innerEp.spec.assertion[0]))
-        {
-            // We know that innerEp.spec.assertion is an Observe(Inbound(...)). Also, if
-            // innerEp.spec.analysis exists, it will be consonant with innerEp.spec.assertion.
-            // Beware of completely-constant patterns, which cause skeleton to be null!
-            this.hookEndpointLifecycle(innerEp, this.outerFacet.addEndpoint(() => {
-                const assertion = Observe(innerEp.spec.assertion[0][0]);
-                const h = innerEp.spec.analysis;
-                const innerCallback = h.callback;
-                const callback = (innerCallback === void 0) ? void 0 :
-                    function (evt: EventType, captures: Array<Value>) {
-                        innerCallback.call(this, evt, captures);
-                        innerDs.start();
-                    };
-                const analysis: Analysis | null = (h === null) ? null :
-                    (h.skeleton === void 0
-                        ? {
-                            skeleton: void 0,
-                            constPaths: h.constPaths,
-                            constVals: h.constVals.map((v) => v[0]),
-                            capturePaths: h.capturePaths.map((p) => p.slice(1)),
-                            assertion,
-                            callback
-                        }
-                        : {
-                            skeleton: h.skeleton[1],
-                            constPaths: h.constPaths.map((p) => p.slice(1)),
-                            constVals: h.constVals,
-                            capturePaths: h.capturePaths.map((p) => p.slice(1)),
-                            assertion,
-                            callback
-                        });
-                return { assertion, analysis };
-            }, false));
-        }
+
+        const innerAssertion = innerEp.spec.assertion;
+        if (!Observe.isClassOf(innerAssertion)) return;
+        const wrapper = innerAssertion[0];
+        if (!Inbound.isClassOf(wrapper)) return;
+
+        // We know that innerAssertion is an Observe(Inbound(...)). Also, if
+        // innerEp.spec.analysis exists, it will be consonant with innerAssertion. Beware of
+        // completely-constant patterns, which cause skeleton to be null!
+
+        const innerDs = this;
+        this.hookEndpointLifecycle(innerEp, this.outerFacet.addEndpoint(() => {
+            const assertion = Observe(wrapper[0]);
+            const h = innerEp.spec.analysis!;
+            const innerCallback = h.callback;
+            const callback = (innerCallback === void 0) ? void 0 :
+                function (evt: EventType, captures: Array<Value>) {
+                    innerCallback.call(null, evt, captures);
+                    innerDs.start();
+                };
+            const analysis: Analysis | null = (h === null) ? null :
+                (h.skeleton === null
+                    ? {
+                        skeleton: null,
+                        constPaths: h.constPaths,
+                        constVals: h.constVals.map(v => (v as Record)[0]),
+                        capturePaths: h.capturePaths.map(p => p.slice(1)),
+                        assertion,
+                        callback
+                    }
+                    : {
+                        skeleton: h.skeleton.members[0],
+                        constPaths: h.constPaths.map(p => p.slice(1)),
+                        constVals: h.constVals,
+                        capturePaths: h.capturePaths.map(p => p.slice(1)),
+                        assertion,
+                        callback
+                    });
+            return { assertion, analysis };
+        }, false));
     }
 
     adjustIndex(a: Value, count: number) {

packages/core/src/runtime/skeleton.ts

@@ -17,7 +17,7 @@
 //---------------------------------------------------------------------------
 
 import { IdentitySet } from './idcoll.js';
-import { is, Value, Record, Set, Dictionary, canonicalString } from 'preserves';
+import { is, Value, Record, Set, Dictionary, canonicalString, preserves } from 'preserves';
 
 import { Bag, ChangeDescription } from './bag.js';
 import { Discard, Capture, Observe } from './assertions.js';
@@ -33,7 +33,8 @@ export enum EventType {
 export type HandlerCallback = (eventType: EventType, bindings: Array<Value>) => void;
 
 export type Shape = string;
-export type Skeleton = null | { shape: Shape, members: Skeleton[] };
+export type NonEmptySkeleton = { shape: Shape, members: Skeleton[] };
+export type Skeleton = null | NonEmptySkeleton;
 export type Path = Array<number>;
 export interface Analysis {
     skeleton: Skeleton;
@@ -58,10 +59,10 @@ export class Index {
             constValMap = new Dictionary();
             continuation.cachedAssertions.forEach((a) => {
                 const key = projectPaths(a, constPaths);
-                let leaf = constValMap.get(key);
+                let leaf = constValMap!.get(key);
                 if (!leaf) {
                     leaf = new Leaf();
-                    constValMap.set(key, leaf);
+                    constValMap!.set(key, leaf);
                 }
                 leaf.cachedAssertions.add(a);
             });
@@ -76,7 +77,7 @@ export class Index {
         if (!handler) {
             const cachedCaptures = new Bag();
             leaf.cachedAssertions.forEach((a) =>
-                cachedCaptures._items.update(projectPaths(a, capturePaths), n => n + 1, 0));
+                cachedCaptures._items.update(projectPaths(a, capturePaths), n => n! + 1, 0));
             handler = new Handler(cachedCaptures);
             leaf.handlerMap.set(capturePaths, handler);
         }
@@ -159,7 +160,7 @@ class Node {
     }
 
     extend(skeleton: Skeleton): Continuation {
-        const path = [];
+        const path: Path = [];
 
         function walkNode(node: Node,
                           popCount: number,
@@ -279,14 +280,14 @@ class Handler {
     }
 }
 
-function classOf(v: any): string | null {
+function classOf(v: any): string {
     if (Record.isRecord(v)) {
         const ci = v.getConstructorInfo();
         return canonicalString(ci.label) + '/' + ci.arity;
     } else if (Array.isArray(v)) {
         return '' + v.length;
     } else {
-        return null;
+        throw new Error(preserves`Cannot route based on ${v}`);
     }
 }
 
@@ -306,10 +307,10 @@ function projectPaths(v: Value, paths: Array<Path>) {
 }
 
 export function analyzeAssertion(a: Value): Analysis {
-    const constPaths = [];
-    const constVals = [];
-    const capturePaths = [];
-    const path = [];
+    const constPaths: Path[] = [];
+    const constVals: Value[] = [];
+    const capturePaths: Path[] = [];
+    const path: Path = [];
 
     function walk(a: Value): Skeleton {
         if (Capture.isClassOf(a)) {
@@ -328,7 +329,7 @@ export function analyzeAssertion(a: Value): Analysis {
             let aa = a as Array<Value>;
             // ^ We know this is safe because it's either Record or Array
             let arity = aa.length;
-            let result = { shape: cls, members: [] };
+            let result: NonEmptySkeleton = { shape: cls, members: [] };
             path.push(0);
             for (let i = 0; i < arity; i++) {
                 path[path.length - 1] = i;
@@ -349,7 +350,7 @@ export function analyzeAssertion(a: Value): Analysis {
 }
 
 export function match(p: Value, v: Value): Array<Value> | false {
-    const captures = [];
+    const captures: Array<Value> = [];
 
     function walk(p: Value, v: Value): boolean {
         if (Capture.isClassOf(p)) {
@@ -376,8 +377,8 @@ export function match(p: Value, v: Value): Array<Value> | false {
     return walk(p, v) ? captures : false;
 }
 
-export function isCompletelyConcrete(p: Value) {
-    function walk(p: Value) {
+export function isCompletelyConcrete(p: Value): boolean {
+    function walk(p: Value): boolean {
         if (Capture.isClassOf(p)) return false;
         if (Discard.isClassOf(p)) return false;
 
@@ -388,8 +389,8 @@ export function isCompletelyConcrete(p: Value) {
     return walk(p);
 }
 
-export function withoutCaptures(p: Value) {
-    function walk(p: Value) {
+export function withoutCaptures(p: Value): Value {
+    function walk(p: Value): Value {
         if (Capture.isClassOf(p)) return walk(p[0]);
         if (Discard.isClassOf(p)) return p;
 

packages/core/src/runtime/stack.ts

@@ -27,8 +27,12 @@ export function push<T>(item: T, rest: Stack<T>): NonEmptyStack<T> {
     return { item, rest };
 }
 
+export function isEmpty<T>(s: Stack<T>): s is null {
+    return s === null;
+}
+
 export function nonEmpty<T>(s: Stack<T>): s is NonEmptyStack<T> {
-    return s !== empty();
+    return s !== null;
 }
 
 export function rest<T>(s: Stack<T>): Stack<T> {
@@ -46,8 +50,9 @@ export function drop<T>(s: Stack<T>, n: number): Stack<T> {
 
 export function dropNonEmpty<T>(s: NonEmptyStack<T>, n: number): NonEmptyStack<T> {
     while (n--) {
-        s = s.rest;
-        if (!nonEmpty(s)) throw new Error("dropNonEmpty popped too far");
+        const next = s.rest;
+        if (!nonEmpty(next)) throw new Error("dropNonEmpty popped too far");
+        s = next;
     }
     return s;
 }

packages/core/src/syntax/codewriter.ts

@@ -12,15 +12,22 @@ export interface SourceMap {
     mappings: string;
 }
 
-export interface Mapping {
-    generatedStartColumn?: number; // zero-based
-    sourceIndex?: number;
-    sourceStartLine?: number; // zero-based (!!)
-    sourceStartColumn?: number; // zero-based
-    nameIndex?: number;
+export interface NoSourceMapping {
+    generatedStartColumn: number; // zero-based
+}
+export interface SourceMapping extends NoSourceMapping {
+    sourceIndex: number;
+    sourceStartLine: number; // zero-based (!!)
+    sourceStartColumn: number; // zero-based
+}
+export interface SourceNameMapping extends SourceMapping {
+    nameIndex: number;
 }
 
-function encodeMapping(entry: Mapping): Array<number> {
+export type NonEmptyMapping = NoSourceMapping | SourceMapping | SourceNameMapping;
+export type Mapping = {} | NonEmptyMapping;
+
+function encodeMapping(entry: NonEmptyMapping): Array<number> {
     const a = [entry.generatedStartColumn];
     if ('sourceIndex' in entry) {
         a.push(entry.sourceIndex);
@@ -33,11 +40,9 @@ function encodeMapping(entry: Mapping): Array<number> {
     return a;
 }
 
-function maybeDelta(newValue: number | undefined, oldValue: number | undefined) {
+function maybeDelta(newValue: number, oldValue: number | undefined): number {
     // console.log('maybeDelta', oldValue, newValue);
-    return (newValue === void 0) ? void 0
-        : (oldValue === void 0) ? newValue
-        : newValue - oldValue;
+    return (oldValue === void 0) ? newValue : newValue - oldValue;
 }
 
 export class CodeWriter {
@@ -45,8 +50,8 @@ export class CodeWriter {
     readonly pos: Pos;
     readonly sources: Array<string> = [];
     readonly chunks: Array<string> = [];
-    readonly mappings: Array<Array<Mapping>> = [];
-    previous: Mapping = {};
+    readonly mappings: Array<Array<NonEmptyMapping>> = [];
+    previous: Partial<SourceNameMapping> = {};
     previousPos: Pos | null = null;
 
     constructor(file: string | null) {
@@ -113,17 +118,21 @@ export class CodeWriter {
             return;
         }
 
-        const n: Mapping = {};
-        n.generatedStartColumn = maybeDelta(this.pos.column, this.previous.generatedStartColumn);
+        let n: NonEmptyMapping = {
+            generatedStartColumn: maybeDelta(this.pos.column, this.previous.generatedStartColumn),
+        };
         this.previous.generatedStartColumn = this.pos.column;
 
         if (p.name !== null) {
             const sourceIndex = this.sourceIndexFor(p.name);
-            n.sourceIndex = maybeDelta(sourceIndex, this.previous.sourceIndex);
+            n = {
+                ... n,
+                sourceIndex: maybeDelta(sourceIndex, this.previous.sourceIndex),
+                sourceStartColumn: maybeDelta(p.column, this.previous.sourceStartColumn),
+                sourceStartLine: maybeDelta(p.line - 1, this.previous.sourceStartLine),
+            };
             this.previous.sourceIndex = sourceIndex;
-            n.sourceStartColumn = maybeDelta(p.column, this.previous.sourceStartColumn);
             this.previous.sourceStartColumn = p.column;
-            n.sourceStartLine = maybeDelta(p.line - 1, this.previous.sourceStartLine);
             this.previous.sourceStartLine = p.line - 1;
         }
 

packages/core/src/syntax/list.ts

@@ -5,10 +5,14 @@ export interface List<T> extends Iterable<T> {
     toArray(): Array<T>;
 }
 
-export function atEnd<T>(xs: List<T>): boolean {
+export function atEnd<T>(xs: List<T>): xs is (List<T> & { item: null, next: null }) {
     return xs.item === null;
 }
 
+export function notAtEnd<T>(xs: List<T>): xs is (List<T> & { item: T, next: List<T> }) {
+    return xs.item !== null;
+}
+
 export class ArrayList<T> implements List<T> {
     readonly items: Array<T>;
     readonly index: number = 0;
@@ -35,9 +39,13 @@ export class ArrayList<T> implements List<T> {
         let i: List<T> = this;
         return {
             next(): IteratorResult<T> {
-                const value = i.item;
-                if (!atEnd(i)) i = i.next;
-                return { done: atEnd(i), value };
+                if (notAtEnd(i)) {
+                    const value = i.item;
+                    i = i.next;
+                    return { done: false, value };
+                } else {
+                    return { done: true, value: null };
+                }
             }
         };
     }

packages/core/src/syntax/matcher.ts

@@ -1,6 +1,6 @@
 import { Token, TokenType, Items, Item, isGroup, isToken, isSpace, isTokenType } from './tokens.js';
 import { Pos } from './position.js';
-import { List, ArrayList, atEnd } from './list.js';
+import { List, ArrayList, atEnd, notAtEnd } from './list.js';
 
 //---------------------------------------------------------------------------
 // Patterns over Item
@@ -15,21 +15,24 @@ export const succeed: Pattern<void> = i => [void 0, i];
 export const discard: Pattern<void> = _i => [void 0, noItems];
 export const rest: Pattern<Items> = i => [i.toArray(), noItems];
 export const end: Pattern<void> = i => atEnd(i) ? [void 0, noItems] : null;
-export const pos: Pattern<Pos> = i => [isGroup(i.item) ? i.item.start.start : i.item.start, i];
+export const pos: Pattern<Pos> = i =>
+    notAtEnd(i)
+    ? [isGroup(i.item) ? i.item.start.start : i.item.start, i]
+    : null;
 
 export const newline: Pattern<Item> = i => {
-    while (!atEnd(i) && isTokenType(i.item, TokenType.SPACE)) i = i.next;
-    if (!isTokenType(i.item, TokenType.NEWLINE)) return null;
+    while (notAtEnd(i) && isTokenType(i.item, TokenType.SPACE)) i = i.next;
+    if (!notAtEnd(i) || !isTokenType(i.item, TokenType.NEWLINE)) return null;
     return [i.item, i.next];
 };
 
 export function skipSpace(i: List<Item>): List<Item> {
-    while (!atEnd(i) && isSpace(i.item)) i = i.next;
+    while (notAtEnd(i) && isSpace(i.item)) i = i.next;
     return i;
 }
 
 export function collectSpace(i: List<Item>, acc: Array<Item>): List<Item> {
-    while (!atEnd(i) && isSpace(i.item)) {
+    while (notAtEnd(i) && isSpace(i.item)) {
         acc.push(i.item);
         i = i.next;
     }
@@ -95,7 +98,7 @@ export function exec(thunk: (i: List<Item>) => void): Pattern<void> {
     };
 }
 
-export function map<T, R>(p: Pattern<T>, f: (T) => R): Pattern<R> {
+export function map<T, R>(p: Pattern<T>, f: (t: T) => R): Pattern<R> {
     return i => {
         const r = p(i);
         if (r === null) return null;
@@ -117,6 +120,7 @@ export interface TokenOptions extends ItemOptions {
 export function group<T>(opener: string, items: Pattern<T>, options: GroupOptions = {}): Pattern<T> {
     return i => {
         if (options.skipSpace ?? true) i = skipSpace(i);
+        if (!notAtEnd(i)) return null;
         if (!isGroup(i.item)) return null;
         if (i.item.start.text !== opener) return null;
         const r = items(new ArrayList(i.item.items));
@@ -129,6 +133,7 @@ export function group<T>(opener: string, items: Pattern<T>, options: GroupOption
 export function atom(text?: string | undefined, options: TokenOptions = {}): Pattern<Token> {
     return i => {
         if (options.skipSpace ?? true) i = skipSpace(i);
+        if (!notAtEnd(i)) return null;
         if (!isToken(i.item)) return null;
         if (i.item.type !== (options.tokenType ?? TokenType.ATOM)) return null;
         if (text !== void 0 && i.item.text !== text) return null;
@@ -139,7 +144,7 @@ export function atom(text?: string | undefined, options: TokenOptions = {}): Pat
 export function anything(options: ItemOptions = {}): Pattern<Item> {
     return i => {
         if (options.skipSpace ?? true) i = skipSpace(i);
-        if (atEnd(i)) return null;
+        if (!notAtEnd(i)) return null;
         return [i.item, i.next];
     };
 }
@@ -150,7 +155,7 @@ export function upTo(p: Pattern<any>): Pattern<Items> {
         while (true) {
             const r = p(i);
             if (r !== null) return [acc, i];
-            if (atEnd(i)) break;
+            if (!notAtEnd(i)) break;
             acc.push(i.item);
             i = i.next;
         }
@@ -202,7 +207,7 @@ export function replace<T>(items: Items,
     const walkItems = (items: Items): Items => {
         let i: List<Item> = new ArrayList(items);
         const acc: Items = [];
-        while (!atEnd(i = collectSpace(i, acc))) {
+        while (notAtEnd(i = collectSpace(i, acc))) {
             const r = p(i);
 
             if (r !== null) {

packages/core/src/syntax/reader.ts

@@ -31,12 +31,12 @@ export class LaxReader implements IterableIterator<Item> {
 
         if (m !== null && !this.stack.some(g => g.start.text === m)) {
             if (this.stack.length > 0) {
-                this.stackTop().items.push(t);
+                this.stackTop()!.items.push(t);
                 return 'continue';
             }
         } else {
             while (this.stack.length > 0) {
-                const inner = this.stack.pop();
+                const inner = this.stack.pop()!;
                 if (inner.start.text === m) {
                     inner.end = t;
                 }
@@ -44,7 +44,7 @@ export class LaxReader implements IterableIterator<Item> {
                 if (this.stack.length === 0) {
                     return inner;
                 } else {
-                    const outer = this.stackTop();
+                    const outer = this.stackTop()!;
                     outer.items.push(inner);
                     if (inner.start.text === m) {
                         return 'continue';
@@ -56,35 +56,50 @@ export class LaxReader implements IterableIterator<Item> {
         return 'eof';