fix(javascript): preserve alias and container uncertainty

src/domain/javascript/javascriptSemanticAnalysis.dataflow.test.ts

@@ -209,6 +209,17 @@ describe("JavaScript semantic analysis: read-modify-write", () => {
       "read",
     ]);
   });
+
+  it("does not model a compound binding write as a competing replacement", () => {
+    const ir = analyzeJavaScriptSemantics(`
+      let count = 1;
+      count += 2;
+    `);
+
+    expect(topLevelBinding(ir, "count").value).toMatchObject({
+      status: "unknown",
+    });
+  });
 });
 
 describe("JavaScript semantic analysis: dataflow 2", () => {
@@ -448,21 +459,36 @@ describe("nonfinite static values", () => {
 
 describe("binding write invalidation", () => {
   it.each([
-    "let value = 1; value++; const observed = value;",
-    "let value = 1; --value; const observed = value;",
-    'let value = "old"; [value] = ["new"]; const observed = value;',
-    'let value = "old"; ({key: value} = {key: "new"}); const observed = value;',
-    'let value = "old"; for (value of ["new"]) {} const observed = value;',
-    'let value = "old"; for (value in {new: true}) {} const observed = value;',
-  ])("does not retain an exact initializer across %s", (source) => {
-    const ir = analyzeJavaScriptSemantics(source);
-    expect(topLevelBinding(ir, "observed").value.status).toBe("ambiguous");
-    expect(
-      topLevelBinding(ir, "value").definitions.some(
-        ({ kind }) => kind === "assignment",
-      ),
-    ).toBe(true);
-  });
+    ["let value = 1; value++; const observed = value;", "unknown"],
+    ["let value = 1; --value; const observed = value;", "unknown"],
+    [
+      'let value = "old"; [value] = ["new"]; const observed = value;',
+      "ambiguous",
+    ],
+    [
+      'let value = "old"; ({key: value} = {key: "new"}); const observed = value;',
+      "ambiguous",
+    ],
+    [
+      'let value = "old"; for (value of ["new"]) {} const observed = value;',
+      "ambiguous",
+    ],
+    [
+      'let value = "old"; for (value in {new: true}) {} const observed = value;',
+      "ambiguous",
+    ],
+  ] as const)(
+    "does not retain an exact initializer across %s",
+    (source, status) => {
+      const ir = analyzeJavaScriptSemantics(source);
+      expect(topLevelBinding(ir, "observed").value.status).toBe(status);
+      expect(
+        topLevelBinding(ir, "value").definitions.some(
+          ({ kind }) => kind === "assignment",
+        ),
+      ).toBe(true);
+    },
+  );
 
   it("does not treat destructuring keys or member owners as assigned bindings", () => {
     const ir = analyzeJavaScriptSemantics(`

src/domain/javascript/javascriptSemanticAnalysis.member_mutations.test.ts

@@ -76,6 +76,85 @@ describe("JavaScript semantic values after explicit property mutations", () => {
     ).toEqual({ status: "literal", value: "initial" });
   });
 
+  it("does not propagate writes through an alias after an unconditional rebind", () => {
+    expect(
+      resultValue(`
+        const shared = { mode: "initial" };
+        let alias = shared;
+        alias = { mode: "other" };
+        alias.mode = "updated";
+        return shared.mode;
+      `),
+    ).toEqual({ status: "literal", value: "initial" });
+  });
+
+  it.each([
+    'if (flag) alias = { mode: "other" }; alias.mode = "updated";',
+    'flag && (alias = { mode: "other" }); alias.mode = "updated";',
+    'flag ||= (alias = { mode: "other" }); alias.mode = "updated";',
+    'alias ||= { mode: "other" }; alias.mode = "updated";',
+    'alias ??= { mode: "other" }; alias.mode = "updated";',
+  ])(
+    "keeps possible source aliases unknown across conditional rebinds",
+    (body) => {
+      expect(
+        resultValue(`
+        const shared = { mode: "initial" };
+        let alias = shared;
+        ${body}
+        return shared.mode;
+      `)?.status,
+      ).toBe("unknown");
+    },
+  );
+
+  it("keeps mutation under a bare conditional unknown across a rebind", () => {
+    expect(
+      resultValue(`
+        const shared = { mode: "initial" };
+        let alias = shared;
+        alias = { mode: "other" };
+        if (flag) alias.mode = "updated";
+        return shared.mode;
+      `)?.status,
+    ).toBe("unknown");
+  });
+
+  it("does not treat a short-circuit assignment RHS as an unconditional value", () => {
+    expect(
+      resultValue(`
+        let value;
+        value &&= 2;
+        return value;
+      `)?.status,
+    ).toBe("unknown");
+  });
+
+  it("keeps possible alias mutations conservative across short-circuit assignment", () => {
+    expect(
+      resultValue(`
+        const shared = { mode: "initial" };
+        let alias = shared;
+        alias &&= { mode: "other" };
+        alias.mode = "updated";
+        return shared.mode;
+      `)?.status,
+    ).toBe("unknown");
+  });
+
+  it("propagates short-circuit assignment mutations to the RHS alias candidate", () => {
+    expect(
+      resultValue(`
+        const shared = { mode: "initial" };
+        const other = { mode: "other" };
+        let alias = shared;
+        alias &&= other;
+        alias.mode = "updated";
+        return other.mode;
+      `)?.status,
+    ).toBe("unknown");
+  });
+
   it("retains ordinary immutable object and array projection", () => {
     expect(
       resultValue(

src/domain/javascript/javascriptSemanticAnalysis.ts

@@ -13,8 +13,8 @@ import {
   collectSemanticReferences,
   immutableSemanticBindings,
   immutableSemanticScopes,
-  semanticStaticPropertyKey,
 } from "./javascriptSemanticProjection.js";
+import { semanticStaticPropertyKey } from "./javascriptAstValues.js";
 import type {
   JavaScriptSemanticAnalysisState,
   JavaScriptSemanticBindingState,
@@ -35,7 +35,8 @@ import {
   resolveSemanticModuleCallables,
 } from "./javascriptSemanticReturns.js";
 import { collectJavaScriptDerivedSemantics } from "./javascriptSemanticDerivedAnalysis.js";
-import { propertyName, range } from "./javascriptStaticAnalysisHelpers.js";
+import { range } from "./javascriptStaticAnalysisHelpers.js";
+import { propertyName } from "./javascriptAstValues.js";
 import { semanticCoverage } from "./javascriptSemanticCoverage.js";
 import { semanticResourceLimitsIn } from "./javascriptSemanticResourceLimits.js";
 import {
@@ -409,7 +410,16 @@ const bindInnerDeclaration = (
     });
   else if (t.isAssignmentExpression(node)) {
     if (t.isIdentifier(node.left))
-      addAssignment(node.left, node.right, scope, state);
+      addAssignment(
+        node.left,
+        node.operator === "=" ||
+          node.operator === "||=" ||
+          node.operator === "??="
+          ? node.right
+          : node,
+        scope,
+        state,
+      );
     else
       for (const identifier of assignedPatternIdentifiers(node.left))
         addAssignment(identifier, node, scope, state);

src/domain/javascript/javascriptSemanticMemberMutations.ts

@@ -3,6 +3,7 @@ import * as t from "@babel/types";
 import {
   resolveSemanticBindingState,
   type JavaScriptSemanticAnalysisState,
+  type JavaScriptSemanticBindingState,
 } from "./javascriptSemanticState.js";
 import { evaluateSemanticBinding } from "./javascriptSemanticValues.js";
 import { traverseJavaScriptAst } from "./javascriptSemanticTraversal.js";
@@ -15,10 +16,17 @@ export const collectSemanticMemberMutations = (
   program: t.Program,
   state: JavaScriptSemanticAnalysisState,
 ): void => {
+  const parents = new WeakMap<t.Node, t.Node>();
+  traverseJavaScriptAst(program, {
+    enter: (node, parent) => {
+      if (parent !== null) parents.set(node, parent);
+    },
+  });
   const markValue = (
     node: t.Node,
     path: PropertyPath,
     bindings: ReadonlySet<string>,
+    mutation: t.Node,
   ): void => {
     if (t.isIdentifier(node)) {
       const binding = resolveSemanticBindingState(state, node, node.name);
@@ -27,11 +35,16 @@ export const collectSemanticMemberMutations = (
       if (value.status === "literal" || value.status === "union") return;
       binding.mutatedPaths.push(path);
       const nested = new Set([...bindings, binding.bindingId]);
-      for (const initializer of binding.initializers)
+      for (const initializer of mutationInitializers(
+        binding,
+        mutation,
+        parents,
+      ))
         markValue(
           initializer.node,
           [...initializer.projection, ...path],
           nested,
+          mutation,
         );
       return;
     }
@@ -47,43 +60,130 @@ export const collectSemanticMemberMutations = (
         );
         current = current.object;
       }
-      markValue(current, [...members.reverse(), ...path], bindings);
+      markValue(current, [...members.reverse(), ...path], bindings, mutation);
       return;
     }
     for (const value of referencedValues(node, path))
-      markValue(value.node, value.path, bindings);
+      markValue(value.node, value.path, bindings, mutation);
   };
-  const markTarget = (node: t.Node): void => {
+  const markTarget = (node: t.Node, mutation: t.Node): void => {
     if (t.isMemberExpression(node) || t.isOptionalMemberExpression(node))
       markValue(
         node.object,
         [semanticStaticPropertyKey(node.property, node.computed)],
         new Set(),
+        mutation,
       );
-    else if (t.isRestElement(node)) markTarget(node.argument);
-    else if (t.isAssignmentPattern(node)) markTarget(node.left);
+    else if (t.isRestElement(node)) markTarget(node.argument, mutation);
+    else if (t.isAssignmentPattern(node)) markTarget(node.left, mutation);
     else if (t.isArrayPattern(node)) {
       for (const element of node.elements)
-        if (element !== null) markTarget(element);
+        if (element !== null) markTarget(element, mutation);
     } else if (t.isObjectPattern(node)) {
       for (const property of node.properties)
         markTarget(
           t.isRestElement(property) ? property.argument : property.value,
+          mutation,
         );
     }
   };
   traverseJavaScriptAst(program, {
     enter: (node) => {
-      if (t.isAssignmentExpression(node)) markTarget(node.left);
-      else if (t.isUpdateExpression(node)) markTarget(node.argument);
+      if (t.isAssignmentExpression(node)) markTarget(node.left, node);
+      else if (t.isUpdateExpression(node)) markTarget(node.argument, node);
       else if (t.isUnaryExpression(node, { operator: "delete" }))
-        markTarget(node.argument);
+        markTarget(node.argument, node);
       else if (t.isForOfStatement(node) || t.isForInStatement(node))
-        markTarget(node.left);
+        markTarget(node.left, node);
     },
   });
 };
 
+interface StatementPosition {
+  readonly body: readonly t.Statement[];
+  readonly index: number;
+}
+
+const statementPosition = (
+  statement: t.Statement,
+  parents: WeakMap<t.Node, t.Node>,
+): StatementPosition | null => {
+  const parent = parents.get(statement);
+  if (!t.isProgram(parent) && !t.isBlockStatement(parent)) return null;
+  const index = parent.body.indexOf(statement);
+  return index < 0 ? null : { body: parent.body, index };
+};
+
+const directInitializerPosition = (
+  node: t.Node,
+  parents: WeakMap<t.Node, t.Node>,
+): StatementPosition | null => {
+  const parent = parents.get(node);
+  if (t.isVariableDeclarator(parent) && parent.init === node) {
+    const declaration = parents.get(parent);
+    return t.isVariableDeclaration(declaration)
+      ? statementPosition(declaration, parents)
+      : null;
+  }
+  if (
+    t.isAssignmentExpression(parent) &&
+    parent.operator === "=" &&
+    parent.right === node &&
+    t.isIdentifier(parent.left)
+  ) {
+    const statement = parents.get(parent);
+    return t.isExpressionStatement(statement) && statement.expression === parent
+      ? statementPosition(statement, parents)
+      : null;
+  }
+  return null;
+};
+
+const directMutationPosition = (
+  node: t.Node,
+  parents: WeakMap<t.Node, t.Node>,
+): StatementPosition | null => {
+  if (
+    !t.isAssignmentExpression(node) &&
+    !t.isUpdateExpression(node) &&
+    !t.isUnaryExpression(node, { operator: "delete" })
+  )
+    return null;
+  const statement = parents.get(node);
+  return t.isExpressionStatement(statement) && statement.expression === node
+    ? statementPosition(statement, parents)
+    : null;
+};
+
+const mutationInitializers = (
+  binding: JavaScriptSemanticBindingState,
+  mutation: t.Node,
+  parents: WeakMap<t.Node, t.Node>,
+): JavaScriptSemanticBindingState["initializers"] => {
+  if (binding.initializers.length < 2) return binding.initializers;
+  const mutationPosition = directMutationPosition(mutation, parents);
+  if (mutationPosition === null) return binding.initializers;
+  const positions = binding.initializers.map(({ node }) =>
+    directInitializerPosition(node, parents),
+  );
+  if (
+    positions.some(
+      (position) =>
+        position === null ||
+        position.body !== mutationPosition.body ||
+        position.index >= mutationPosition.index,
+    )
+  )
+    return binding.initializers;
+  const latestIndex = positions.reduce(
+    (latest, position) => Math.max(latest, position?.index ?? -1),
+    -1,
+  );
+  return binding.initializers.filter(
+    (_, index) => positions[index]?.index === latestIndex,
+  );
+};
+
 interface ReferencedValue {
   readonly node: t.Node;
   readonly path: PropertyPath;
@@ -141,5 +241,7 @@ const referencedValues = (
       { node: node.left, path },
       { node: node.right, path },
     ];
+  if (t.isAssignmentExpression(node, { operator: "&&=" }))
+    return [{ node: node.right, path }];
   return [];
 };

src/domain/javascript/javascriptSemanticValues.ts

@@ -4,12 +4,12 @@ import { semanticSlotAtPath } from "./javascriptSemanticSlots.js";
 
 import { invalidateSemanticMutationPath } from "./javascriptSemanticMutationValues.js";
 
+import type { JavaScriptBindingProvenance } from "./javascriptSemanticIr.js";
 import type {
-  JavaScriptBindingProvenance,
   JavaScriptSemanticProperty,
   JavaScriptSemanticResourceLimit,
   JavaScriptSemanticValue,
-} from "./javascriptSemanticIr.js";
+} from "./javascriptSemanticValueTypes.js";
 import {
   resolveSemanticBindingState,
   type JavaScriptSemanticAnalysisState,
@@ -17,7 +17,10 @@ import {
 } from "./javascriptSemanticState.js";
 import { semanticRequireOrigin } from "./javascriptSemanticRequireOrigin.js";
 import { compareCodePoints } from "../canonicalOrdering.js";
-import { semanticStaticPropertyKey } from "./javascriptAstValues.js";
+import {
+  readExactJavaScriptLiteral,
+  semanticStaticPropertyKey,
+} from "./javascriptAstValues.js";
 import {
   semanticAmbiguousProvenance,
   semanticLocalProvenance,
@@ -26,10 +29,8 @@ import {
   uniqueSemanticOrigins,
 } from "./javascriptSemanticProvenance.js";
 import {
-  MAX_SEMANTIC_PRIMITIVE_CANDIDATES,
   semanticPrimitiveCandidates as primitiveCandidates,
   semanticPrimitiveSet as primitiveSet,
-  semanticPrimitiveValue as primitiveValue,
 } from "./javascriptSemanticPrimitives.js";
 import {
   SEMANTIC_EXPRESSION_DEPTH_LIMIT,
@@ -120,6 +121,21 @@ const evaluateBinding = (
       status: "unknown",
       reason: `Binding ${binding.name} has no constant initializer.`,
     };
+  if (
+    binding.initializers.some(
+      ({ node }) =>
+        t.isUpdateExpression(node) ||
+        (t.isAssignmentExpression(node) &&
+          node.operator !== "=" &&
+          node.operator !== "&&=" &&
+          node.operator !== "||=" &&
+          node.operator !== "??="),
+    )
+  )
+    return {
+      status: "unknown",
+      reason: `Binding ${binding.name} has a compound or update write.`,
+    };
   if (binding.initializers.length > 1)
     return {
       status: "ambiguous",
@@ -154,7 +170,7 @@ const evaluateExpression = (
 ): JavaScriptSemanticValue => {
   if (context.expressionDepth > SEMANTIC_EXPRESSION_DEPTH_LIMIT)
     return semanticResourceLimitUnknown("expression-depth");
-  const literal = primitiveValue(node);
+  const literal = readExactJavaScriptLiteral(node);
   if (literal.found) return { status: "literal", value: literal.value };
   if (t.isIdentifier(node)) {
     const binding = resolveSemanticBindingState(context.state, node, node.name);
@@ -408,7 +424,7 @@ const addPrimitiveValues = (
     if (isSemanticResourceLimit(rightValue)) return rightValue;
     return { status: "unknown", reason: "Non-primitive addition." };
   }
-  if (left.length > MAX_SEMANTIC_PRIMITIVE_CANDIDATES / right.length)
+  if (left.length > SEMANTIC_PRIMITIVE_CANDIDATE_LIMIT / right.length)
     return semanticResourceLimitUnknown("primitive-candidates");
   if (exceedsSemanticPrimitiveAdditionByteBudget(left, right))
     return semanticResourceLimitUnknown("primitive-bytes");