Fix reverse mapped type inference when all properties are context-sensitive

[Devansh Jethmalani (devanshj)]

Fixes #64251

The code change feels wrong because there should be a reason why the original code was like that but given there are no tests failing (well there's one baseline change but it doesn't look like a bad change to me) so I thought of opening this PR.

Happy to be proven wrong by showing some counter bad changes. Maybe I can be a little more conservative and target only the linked issue case.

[Copilot]

🔵 Needs a closer look

The unresolved inference issue prevents correctly inferring the generic context member.

Pull request overview

Fixes reverse-mapped type inference when all properties are context-sensitive.

Changes:

• Broadens partial inferability for non-empty object literals.
• Adds regression coverage and compiler baselines.
• Updates existing inference expectations.

The callback is contextually typed, but the generic D["context"] remains inferred as object rather than { foo: number }.

File summaries

File	Summary
tsc/testdata/tests/cases/compiler/reverseMappedTypeWithAllContextSensitiveProperties.ts	Adds regression coverage.
tsc/testdata/baselines/reference/compiler/reverseMappedTypeWithAllContextSensitiveProperties.types	Records inferred types.
tsc/testdata/baselines/reference/compiler/reverseMappedTypeWithAllContextSensitiveProperties.symbols	Records symbol mappings.
tsc/testdata/baselines/reference/compiler/reverseMappedPartiallyInferableTypes.types	Updates inference expectations.
tsc/internal/checker/inference.go	Adjusts reverse-mapped type inferability; generic context inference remains incomplete.

Review details

Suppressed comments (1)

tsc/internal/checker/inference.go:1060

• This change only makes the callback contextually typed; it does not make the generic D infer its context member. The generated .types baseline for this test still reports the call result as { context: object; ... }, so a consumer of const machine = createMachine(...) cannot access machine.context.foo even though the callback parameter can. Please add a return-type assertion to the regression test and adjust the inference path so D["context"] is inferred as { foo: number }, not just used to contextualize entry.

	return t.objectFlags&ObjectFlagsNonInferrableType == 0 || isObjectLiteralType(t) && len(c.getPropertiesOfType(t)) != 0 || isTupleType(t) && core.Some(c.getElementTypes(t), c.isPartiallyInferableType)

• Files reviewed: 5/5 changed files
• Comments generated: 0
• Review effort level: Lite (auto)

Note

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[Devansh Jethmalani (devanshj)]

a consumer of const machine = createMachine(...) cannot access machine.context.foo

nice catch copilot fixed it! (just needed to tweak the userland types, the compiler is already good)

[Ryan Cavanaugh (RyanCavanaugh)]

TypeScript Bot (@typescript-bot) test it

[typescript-automation]

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