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Probe forwarded tuples without interning types

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Recognizing the empty-tuple representation interned the unit-only union,
and a rest parameter's IR type was mapped before checking that it is a
tuple at all. Both shifted union ids in programs with ordinary array rest
parameters that read `.length`. Probe through the checker and registry
lookups only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Malte Ubl
2026-10-19 15:15:20 -07:00
co-authored by Claude Opus 5.5
parent cfb50d16e2
commit 46d12eb1e1
1 changed files with 16 additions and 13 deletions
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packages/compiler/src/frontend/lowering/typed-arguments.ts
+16 -13
View File
@@ -1,16 +1,8 @@
import * as ts from "../ts7/adapter.js";
import { bodyReadsArguments } from "../arguments-usage.js";
import { isJsSourceFile, locOf } from "../program.js";
import { unitOnlyUnion } from "../type-mapper.js";
import {
DYN,
type IrExpr,
type IrLocal,
type IrStmt,
type IrType,
arrayOf,
typeEquals,
} from "../../ir/ir.js";
import { restTupleElementTypes, unitOnlyUnion } from "../type-mapper.js";
import { DYN, type IrExpr, type IrLocal, type IrStmt, type IrType, arrayOf } from "../../ir/ir.js";
import type { Lowerer } from "./lowerer.js";
import { captureContextArguments } from "./function-context.js";
import { isThisParameter, type ParamShape } from "./call-signatures.js";
@@ -325,7 +317,9 @@ export function forwardedTupleType(lowerer: Lowerer, node: ts.Expression): IrTyp
ts.isParameter(decl) &&
decl.dotDotDotToken !== undefined &&
ts.isIdentifier(decl.name) &&
!isJsSourceFile(decl.getSourceFile())
!isJsSourceFile(decl.getSourceFile()) &&
// Checker-only probe first: an ordinary array rest never maps here.
restTupleElementTypes(lowerer.typeOf(operand), lowerer.typeCtx) !== null
) {
const t = lowerer.mapTypeOf(lowerer.typeOf(operand));
if (t && isTupleValueType(lowerer, t)) return t;
@@ -335,8 +329,17 @@ export function forwardedTupleType(lowerer: Lowerer, node: ts.Expression): IrTyp
function isTupleValueType(lowerer: Lowerer, t: IrType): boolean {
if (t.kind === "record") return lowerer.shapes.get(t.shapeId)?.tuple === true;
// The empty tuple's representation (mapType's `[]` rule).
return typeEquals(t, arrayOf(unitOnlyUnion(lowerer.unions)));
// The empty tuple's representation (mapType's `[]` rule): an array over
// the unit-only union. Looked up, never interned, so probing a value
// leaves the registries untouched.
if (t.kind !== "array" || t.elem.kind !== "union") return false;
const arms = lowerer.unions.get(t.elem.unionId)?.arms;
return (
arms !== undefined &&
arms.length === 2 &&
arms.some((a) => a.kind === "nullT") &&
arms.some((a) => a.kind === "undefinedT")
);
}
/** The positional reads of a forwarded tuple value (already saved in a