Match Strada's behavior to allow satisfying recursive indexed access

[RyanCavanaugh]

Authored by copilot

Fixes microsoft/TypeScript#63568

Analysis

The regression came from Corsa not matching Strada’s base-constraint cache model.

In Strada, base-constraint resolution has two distinct caches:

• immediateBaseConstraint, cached on every Type
• resolvedBaseConstraint, cached on instantiable/union/intersection types

The key Strada implementation is getResolvedBaseConstraint. It computes resolvedBaseConstraint by calling an inner getImmediateBaseConstraint, and recursive base-constraint walks go through an inner getBaseConstraint helper. Circularity tracking is also keyed to TypeSystemPropertyName.ImmediateBaseConstraint, and resolutionTargetHasProperty checks immediateBaseConstraint at checker.ts#L11525-L11526.

Corsa had collapsed this into a single resolvedBaseConstraint cache and passed an explicit recursion stack through getResolvedBaseConstraint(t, stack). That made conditional/indexed-access constraint recovery diverge in recursive cases like:

FromSchema<Context, Context[keyof Context]>["values"]

In the reduced repro, the checker needs to keep advancing the conditional/indexed-access constraint chain far enough to see the values: string shape. The old Corsa model treated one of those recursive conditional constraints as circular too early, so Wrapped<FromSchema<...>> failed the Type constraint even though Strada accepts the type parameter default.

Fix

This ports Corsa’s base-constraint machinery closer to Strada

The main changes are:

1. Added immediateBaseConstraint to Corsa’s ConstrainedType, matching Strada’s separate immediate/resolved cache split:

   • Strada: types.ts#L6452
   • Corsa: [internal/checker/types.go](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)

2. Renamed the type-resolution property from resolved-base-constraint tracking to immediate-base-constraint tracking:

   • Strada enum/property check: [checker.ts#L1331](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#), [checker.ts#L11525-L11526](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)
   • Corsa equivalent: [internal/checker/checker.go](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)

3. Refactored Corsa’s getResolvedBaseConstraint to mirror Strada’s structure:

   • inner getImmediateBaseConstraint
   • inner getBaseConstraint
   • resolvedBaseConstraint = getImmediateBaseConstraint(t)
   • Strada reference: [checker.ts#L15322-L15367](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)
   • Corsa implementation: [internal/checker/checker.go](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)

4. Updated computeBaseConstraint to use the inner getBaseConstraint helper, matching the Strada flow through type parameters, unions/intersections, index types, indexed accesses, substitutions, and tuples:

   • Strada reference: [checker.ts#L15369-L15440](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)
   • Corsa implementation: [internal/checker/checker.go](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)

5. Kept Corsa’s existing safeguard for pathological recursive conditional constraints, but adjusted indexed-access check types to use the regular constraint path when appropriate. This preserves the existing infinite-constraint behavior while allowing the #63568 recursive mapped/default constraint case to resolve like Strada.

6. Added a regression test:

   • [testdata/tests/cases/compiler/recursiveMappedTypeDefaultConstraint.ts](https://github.com/microsoft/typescript-go/compare/main...RyanCavanaugh:fix63568?expand=1#)

The baseline update also improves the existing infiniteConstraints submodule output by removing one excessive-stack-depth diagnostic while retaining the intended indexing error.

[Copilot]

Pull request overview

Ports the TypeScript-Go checker’s base-constraint caching and recursion handling to more closely match upstream TypeScript (“Strada”), fixing a regression where recursive indexed-access/conditional constraints were treated as circular too early and caused constraint satisfaction failures (TypeScript#63568).

Changes:

• Split base-constraint caching into immediateBaseConstraint vs resolvedBaseConstraint, and key circularity tracking off the immediate cache.
• Refactor getResolvedBaseConstraint/computeBaseConstraint to mirror Strada’s structure and recursion flow, including a targeted tweak for indexed-access constraints inside distributive conditional constraints.
• Add a regression test and update baselines (including reducing one previously-emitted “Excessive stack depth” diagnostic in infiniteConstraints).

Show a summary per file

File	Description
internal/checker/checker.go	Reworks base-constraint computation/caching and circularity tracking to align with Strada and fix premature circularity.
internal/checker/types.go	Adds immediateBaseConstraint to ConstrainedType alongside resolvedBaseConstraint.
internal/checker/utilities.go	Updates call site for the new getResolvedBaseConstraint signature.
testdata/tests/cases/compiler/recursiveMappedTypeDefaultConstraint.ts	New regression repro covering recursive mapped/default constraint satisfaction.
testdata/baselines/reference/compiler/recursiveMappedTypeDefaultConstraint.*	Adds baselines for the new compiler test.
testdata/baselines/reference/submodule/compiler/infiniteConstraints.errors.txt*	Updates submodule baseline to reflect diagnostic changes from the new constraint behavior.

Copilot's findings

• Files reviewed: 9/9 changed files
• Comments generated: 0